CN112088487A - Electric motor system and turbo compressor including the same - Google Patents

Abstract

The invention provides an electric motor system and a turbo compressor including the same. The motor system (30) includes: a bearingless motor (40, 50); power supply units (61, 62) for applying voltages to armature windings (46a to 46c, 56a to 56c) and support windings (47a to 47c, 57a to 57c) provided on stators (44, 54) of bearingless motors (40, 50), respectively; and a control unit (60) that controls the power supply units (61, 62) such that one of an armature voltage VA that IS a voltage applied to the armature windings (46 a-46 c, 56 a-56 c) and a support current IS that IS a current flowing through the support windings (47 a-47 c, 57 a-57 c) IS increased and the other IS decreased. As a result, the bearingless motor can be operated in accordance with a predetermined power source capacity.

Description

Electric motor system and turbo compressor including the same

technical field

The present invention relates to an electric motor system and a turbo compressor including the electric motor system.

Background technique

Conventionally, there has been known a bearingless motor having a motor function for driving the rotor to rotate and a magnetic bearing function for controlling the radial position of the rotor (for example, Patent Document 1). In the bearingless motor of this document, the supporting force for maintaining the magnetic linearity and magnetically supporting the rotor can be efficiently generated.

Patent Document 1: Japanese Laid-Open Patent Publication No. 2004-336968

SUMMARY OF THE INVENTION

- The technical problem to be solved by the invention -

When operating a bearingless motor, it is necessary to provide a power supply for supplying electric power to the bearingless motor. The power supply capacity of such power supplies is limited, and the current and voltage that can be output are limited. However, few attempts have been made to make bearingless motors operate with the limited power supply capacity described above.

An object of the present invention is to make a bearingless motor operate with a predetermined power supply capacity.

-Technical solutions to solve technical problems-

The technical solution of the first aspect of the present invention is directed to the motor system 30 . The motor system 30 includes: a drive shaft 31, which drives a load 21 to rotate; bearingless motors 40, 50, respectively having rotors 41, 51, and provided with armature windings 46a-46c, 56a-56c and support windings 47a-47c, 57a The stators 44 and 54 of the to 57c drive the drive shaft 31 to rotate and support the radial load of the drive shaft 31 in a non-contact manner; the power supply parts 61 and 62 are used to supply the armature windings 46a to 46c, 56a to 56c and The support windings 47a to 47c and 57a to 57c apply a voltage; and the control unit 60 controls the power supply units 61 and 62 so that one of the armature voltage VA and the support current IS increases and the other decreases, the The armature voltage VA is a voltage applied to the armature windings 46a to 46c and 56a to 56c, and the support current IS is a current flowing through the support windings 47a to 47c and 57a to 57c.

In the technical solution of the first aspect, by increasing one of the armature voltage VA and the bearing current IS and decreasing the other of the armature voltage VA and the bearing current IS, the motor system 30 can be used according to the use of the motor system 30. The armature voltage VA and the support current IS are adjusted within the range of the power supply capacity of the power supply units 61 and 62 according to the operating conditions of various equipment.

A second aspect of the present invention is based on the first aspect, and is characterized in that the control unit 60 controls the power supply units 61 and 62 so that the armature voltage VA increases and the bearing current IS decreases , or the above-mentioned bearing current IS is increased and the above-mentioned armature voltage VA is decreased.

In the technical solution of the second aspect, the radial support force can be maintained, and the support current IS or the armature voltage VA can be reduced.

A third aspect of the present invention is based on the first aspect or the second aspect, wherein the control unit 60 controls the power supply units 61 and 62 to increase the armature voltage VA And the said support current IS does not exceed the predetermined 1st upper limit value.

In the third aspect, the support current IS can be kept from exceeding the first upper limit value, and on the other hand, the armature current IA, which is the current flowing in the armature windings 46a to 46c and 56a to 56c, can be increased. radial bearing force. This is particularly effective when the radial support force is increased in a state where the support current IS reaches the first upper limit value or a value near the first upper limit value.

A fourth aspect of the present invention is based on the technical solution of any one of the above-mentioned first to third technical solutions, wherein the control unit 60 controls the power supply units 61 and 62 so that the support The current IS increases and the above-mentioned armature voltage VA does not exceed the predetermined second upper limit value.

In the fourth aspect, the armature voltage VA can be prevented from exceeding the second upper limit value. However, for example, when the rotational speed of the bearingless motors 40 and 50 is increased, the radial support force caused by the armature current IA may will decline. On the other hand, by increasing the support current IS, the above-mentioned decrease can be compensated by the radial support force by the support current IS.

The technical solution of the fifth aspect of the present invention is based on the technical solution of any one of the technical solution of the first aspect to the technical solution of the fourth aspect, and is characterized in that the control unit 60 controls the power supply units 61 and 62 so that the power The armature voltage VA decreases and the bearing current IS increases, or the bearing current IS decreases and the armature voltage VA increases.

In the technical solution of the fifth aspect, the support current IS or the armature voltage VA can be increased while maintaining the radial support force.

A sixth aspect of the present invention is based on the technical solution of any one of the first technical solution to the fifth technical solution, and is characterized in that the control unit 60 controls the power supply units 61 and 62 so that the electrical The armature voltage VA decreases and the above-mentioned support current IS exceeds the predetermined first lower limit value.

In the technical solution of the sixth aspect, the support current IS can be made to exceed the first lower limit value. Thereby, the heat generation in the support coils 47a-47c and 57a-57c can be utilized as needed, for example.

A seventh aspect of the present invention is based on any one of the first to sixth aspects of the present invention, wherein the control unit 60 controls the power supply units 61 and 62 so that the support The current IS decreases and the above-mentioned armature voltage VA exceeds the predetermined second lower limit value.

In the technical solution of the seventh aspect, the armature voltage VA can be made to exceed the second lower limit value. Thereby, the heat generation in the armature windings 46a-46c and 56a-56c can be utilized as needed, for example.

The technical solution of the eighth aspect of the present invention targets the turbo compressor 12 . The turbo compressor 12 includes: a motor system 30 according to any one of the first to seventh technical solutions; and an impeller 21 connected to the drive shaft 31 of the motor system 30 and serving as the above-mentioned Load 21.

In the technical solution of the eighth aspect, in the turbo compressor 12 , the impeller 21 is driven to rotate by the bearingless motors 40 and 50 .

A ninth aspect of the present invention is based on the sixth aspect of the present invention, characterized in that the turbo compressor 12 is provided in the refrigerant circuit 11 that performs the refrigeration cycle and is configured to use the impeller 21 to compress the refrigerant, When the turbo compressor 12 is operated in the region C where the rotational stall occurs or the surge region D, the control unit 60 controls the power supply units 61 and 62 so that the armature voltage VA increases and the support current IS does not increase. Exceeds the specified first upper limit value.

In the ninth aspect, when the turbo compressor 12 is operated in the region C where the rotational stall occurs or the surge region D, that is, when the load torque of the bearingless motors 40 and 50 is small, the required diameter is When the radial support force is large, the radial support force caused by the armature current IA can be increased. Therefore, even if the support current IS is kept below the first upper limit value, the radial support force of the bearingless motors 40 and 50 can be increased by increasing the armature current IA.

Description of drawings

FIG. 1 is a schematic diagram illustrating a configuration of an air conditioner according to an embodiment;

2 is a longitudinal sectional view illustrating the structure of a turbo compressor;

3 is a transverse cross-sectional view illustrating the structure of the bearingless motor;

FIG. 4 is a diagram for explaining an operation region of the turbo compressor.

Detailed ways

(air conditioner)

FIG. 1 illustrates the configuration of the air conditioner 10 according to the embodiment. The air conditioner 10 includes a refrigerant circuit 11 . The refrigerant circuit 11 includes a turbo compressor 12, a condenser 13, an expansion valve 14, and an evaporator 15, and is configured to perform a refrigeration cycle as a refrigerant cycle. For example, the condenser 13 and the evaporator 15 are constituted by a transverse fin heat exchanger, and the expansion valve 14 is constituted by an electric valve.

(Turbo compressor)

FIG. 2 illustrates the structure of the turbo compressor 12 shown in FIG. 1 . The turbo compressor 12 is provided in the refrigerant circuit 11, and is configured to compress the refrigerant by an impeller 21 to be described later. In this example, the turbo compressor 12 includes a casing 20 , an impeller 21 , and an electric motor system 30 . The motor system 30 includes a drive shaft 31 , a first bearingless motor 40 and a second bearingless motor 50 , a control unit 60 , a first power supply unit 61 and a second power supply unit 62 . In this example, the motor system 30 further includes a first bottoming bearing 71 , a second bottoming bearing 72 , and a thrust magnetic bearing 73 .

In addition, in the following description, an "axial direction" is a rotation axis direction, and is a direction of the axial center of the drive shaft 31, and a "radial direction" is a direction orthogonal to the axial direction of the drive shaft 31. In addition, the "outer peripheral side" is the side away from the axial center of the drive shaft 31 , and the "inner peripheral side" is the side close to the axial center of the drive shaft 31 .

〔case〕

The casing 20 is formed in a cylindrical shape with both ends closed, and is arranged so that the cylindrical axis direction is the horizontal direction. The space in the casing 20 is divided by a wall portion 20a, the space on the right side of the wall portion 20a constitutes an impeller chamber S1 for housing the impeller 21, and the space on the left side of the wall portion 20a constitutes a housing for the first bearingless motor 40 and the second bearingless motor 40. The motor room S2 of the electric motor 50. In addition, the first bearingless motor 40 and the second bearingless motor 50 , the first bottoming bearing 71 and the second bottoming bearing 72 , and the thrust magnetic bearing 73 are accommodated in the motor room S2 , and these are fixed to the motor room S2 on the inner peripheral wall.

[Drive shaft]

The drive shaft 31 is provided to rotate the load 21 (the impeller 21 in this example). In this example, the drive shaft 31 extends in the axial direction within the housing 20 and connects the impeller 21 with the first bearingless motor 40 and the second bearingless motor 50 . Specifically, the impeller 21 is fixed to one end of the drive shaft 31 ; the first bearingless motor 40 and the second bearingless motor 50 are arranged in the middle of the drive shaft 31 . In addition, a disk-shaped portion (hereinafter also referred to as a disk portion 31a) is provided at the other end portion of the drive shaft 31 (ie, the end portion of the drive shaft 31 opposite to the end portion of the drive shaft 31 to which the impeller 21 is fixed). In addition, the disk part 31a is made of a magnetic material (for example, iron).

[Impeller (load)]

The impeller 21 is formed of a plurality of blades so as to have a substantially conical outer shape, and is accommodated in the impeller chamber S1 in a state of being fixed to one end portion of the drive shaft 31 . The suction pipe P1 and the discharge pipe P2 are connected to the impeller chamber S1. The suction pipe P1 is provided to guide the refrigerant (fluid) to the impeller chamber S1 from the outside. The discharge pipe P2 is provided to return the high-pressure refrigerant (fluid) compressed in the impeller chamber S1 to the outside. That is, in this example, the compression mechanism is constituted by the impeller 21 and the impeller chamber S1.

[Bearingless Motor]

The first bearingless motor 40 and the second bearingless motor 50 have the same structure as each other. Therefore, only the structure of the first bearingless motor 40 will be described here.

The first bearingless motor 40 has a stator 44 and a pair of rotors 41, and is configured to drive the drive shaft 31 to rotate and to support a radial load of the drive shaft 31 in a non-contact manner. The rotor 41 is fixed to the drive shaft 31 , and the stator 44 is fixed to the inner peripheral wall of the casing 20 .

As shown in FIG. 3 , in this example, the first bearingless motor 40 is constituted by a consequent pole type bearingless motor.

The rotor 41 of the first bearingless motor 40 has a rotor core 42 and a plurality of (four in this example) permanent magnets 43 embedded in the rotor core 42 . The rotor core 42 is made of a magnetic material (eg, laminated steel plates), and is formed in a cylindrical shape. A shaft hole through which the drive shaft 31 passes is formed in the central portion of the rotor core 42 .

The plurality of permanent magnets 43 have a predetermined angular pitch (in this example, an angular pitch of 90°) with each other in the circumferential direction of the rotor 41 . The outer peripheral surface sides of the four permanent magnets 43 serve as N poles, and a portion of the outer peripheral surface of the rotor core 42 located between the four permanent magnets 43 in the circumferential direction of the rotor 41 functions as an S pole and is a dummy S pole. In addition, the outer peripheral surface side of the four permanent magnets 43 may be an S pole.

The stator 44 of the first bearingless motor 40 is made of a magnetic material (eg, laminated steel plates), and has a back yoke 45 , a plurality of teeth (not shown), and armature windings 46 a to 46 c wound around the teeth and The support windings 47a to 47c are provided. The back yoke portion 45 is configured in a cylindrical shape. The armature windings 46a to 46c and the support windings 47a to 47c are wound around each tooth portion by distributed winding. It should be noted that the armature windings 46a to 46c and the support windings 47a to 47c may be wound around each tooth portion in a concentrated winding method.

The armature windings 46a to 46c are windings wound around the inner peripheral side portion of the tooth portion. The armature windings 46a to 46c are represented by the U-phase armature winding 46a surrounded by a thick solid line in FIG. 3 , the V-phase armature winding 46b surrounded by a thick broken line in FIG. 3 , and the thin solid line in FIG. 3 . The W-phase armature winding 46c shown is surrounded.

The support coils 47a to 47c are coils wound around the outer peripheral side portions of the teeth. The support windings 47a to 47c are shown surrounded by a U-phase support winding 47a surrounded by a thick solid line in FIG. 3 , a V-phase support winding 47b shown surrounded by a thick broken line in FIG. 3 , and shown surrounded by a thin solid line in FIG. 3 . The W-phase support winding 47c is constituted.

〔Bottom Bearing〕

The first bottoming bearing 71 is provided near one end (right end in FIG. 2 ) of the drive shaft 31 , and the second bottoming bearing 72 is provided near the other end of the driving shaft 31 . The first bottoming bearing 71 and the second bottoming bearing 72 are configured so that the driving shaft 31 is operated when the first bearingless motor 40 and the second bearingless motor 50 are not energized (that is, when the driving shaft 31 is not floating). support.

[Thrust Magnetic Bearing]

The thrust magnetic bearing 73 includes a first thrust electromagnet 74a and a second thrust electromagnet 74b, and is configured to support the disk portion 31a of the drive shaft 31 in a non-contact manner by electromagnetic force. Specifically, the first thrust electromagnet 74a and the second thrust electromagnet 74b are formed in annular shapes, respectively, and face each other across the disk portion 31a of the drive shaft 31, and the first thrust electromagnet 74a and the second thrust electromagnet 74a are used. The combined electromagnetic force of the iron 74b supports the disk portion 31a of the drive shaft 31 in a non-contact manner.

[Various sensors]

Various sensors (not shown), such as a position sensor, a current sensor, and a rotational speed sensor, are provided in each part of the motor system 30 . For example, the first bearingless motor 40 and the second bearingless motor 50 are provided with position sensors (not shown) that output detection signals corresponding to the radial (diameter) positions of the rotors 41 and 51, and the thrust magnetic The bearing 73 is provided with a position sensor (not shown) that outputs a detection signal corresponding to a position in the thrust direction (axial direction) of the drive shaft 31 . These position sensors are constituted by, for example, an eddy current type displacement sensor that detects a gap (distance) with the object to be measured.

[Control Department]

The control unit 60 is configured to generate and output an armature voltage command value, a support voltage command value, and a thrust voltage command based on detection signals from various sensors provided in each unit of the motor system 30 and information such as the target rotational speed of the drive shaft 31 . The value is such that the rotational speed of the drive shaft 31 reaches a predetermined target rotational speed in a state where the drive shaft 31 is supported in a non-contact manner. The armature voltage command value is a command value for controlling the voltages supplied to the armature windings 46 a to 46 c and 56 a to 56 c of the first bearingless motor 40 and the second bearingless motor 50 . The support voltage command value is a command value for controlling the voltages supplied to the support windings 47 a to 47 c and 57 a to 57 c of the first bearingless motor 40 and the second bearingless motor 50 . The thrust voltage command value is a command value for controlling the voltage supplied to the windings (not shown) of the first thrust electromagnet 74 a and the second thrust electromagnet 74 b of the thrust magnetic bearing 73 . The control unit 60 includes, for example, an arithmetic processing unit such as a CPU, a storage unit such as a memory that stores programs and information for operating the arithmetic processing unit, and the like.

[Power Supply Department]

The first power supply unit 61 is configured to supply voltages to the armature windings 46a to 46c and 56a to 56c of the first bearingless motor 40 and the second bearingless motor 50 based on the armature voltage command value output from the control unit 60 . The second power supply unit 62 is configured to supply voltages to the support windings 47a to 47c and 57a to 57c of the first bearingless motor 40 and the second bearingless motor 50 based on the support voltage command value output from the control unit 60 . The respective windings 46a to 46c and 56a are controlled by controlling the voltages applied to the armature windings 46a to 46c and 56a to 56c and the support windings 47a to 47c and 57a to 57c of the first bearingless motor 40 and the second bearingless motor 50 . -56c, 47a - 47c, 57a - 57c), the torque and supporting force generated by the first bearingless motor 40 and the second bearingless motor 50 can be controlled. The first power supply unit 61 and the second power supply unit 62 are constituted by, for example, PWM (Pulse Width Modulation) amplifiers. The first power supply unit 61 and the second power supply unit 62 constitute a power supply unit.

(Operation area of turbo compressor)

FIG. 4 is a diagram for explaining an operation region of the turbo compressor 12 . In this figure, the horizontal axis represents the refrigerant mass flow rate, and the vertical axis represents the compression work. The turbo compressor 12 can be operated in a predetermined operation region by being supplied with electric power from the first power supply unit 61 and the second power supply unit 62 .

The predetermined operation region mainly includes a stable operation region A, a high-load torque region B, and a turbulent flow region C inside the surge line indicated by the thick line in FIG. 4 , and a surge region D outside the surge line . In this specification, the high-load torque region B is also referred to as a "region where the maximum driving torque of the turbo compressor 12 is required". In addition, the turbulent flow region C is also referred to as a "region where a rotational stall occurs".

The stable operation region A is the region indicated by the symbol A in FIG. 4 , and in the stable operation region A, the load torque of the impeller 21 and the drive shaft 31 (that is, the torque for driving the impeller 21 and the drive shaft 31 to rotate) It is relatively small and the radial load of the drive shaft 31 is also relatively small.

The high load torque region B is the region indicated by the symbol B in FIG. 4 . In this high load torque region B, the load torque of the impeller 21 and the drive shaft 31 is relatively large, and the radial load of the drive shaft 31 is also relatively large. . The load torque of the impeller 21 and the drive shaft 31 in the turbo compressor 12 is the highest at the upper rightmost point in FIG. 4 in the high load torque region B. As shown in FIG. However, in the high-load torque region B, the radial load of the drive shaft 31 in the turbo compressor 12 is not maximized.

The turbulent flow region C is the region indicated by the symbol C in FIG. 4 , and in this turbulent flow region C, the load torque of the impeller 21 and the drive shaft 31 is relatively small, and the radial load of the drive shaft 31 is relatively large.

The surge region D is the region indicated by the symbol D in FIG. 4 , and the turbo compressor 12 may be temporarily operated in the surge region D in an emergency such as a power failure. In this surge region D, the load torque of the impeller 21 and the drive shaft 31 is relatively small, and the radial load of the drive shaft 31 is relatively large. The radial load of the drive shaft 31 in the turbo compressor 12 is maximum at a predetermined point in the surge region D. As shown in FIG.

(Operation of the control part and the power supply part)

The operation of the control unit 60 , the first power supply unit 61 , and the second power supply unit 62 will be described. The control unit 60 supplies voltages to the armature windings 46a to 46c, the support windings 47a to 47c of the first bearingless motor 40, and the armature windings 56a to 56c and the support windings 57a to 57c of the second bearingless motor 50 to generate armature currents IA and the support current IS, so that the radial support force for supporting the radial load corresponding to the state of the turbo compressor 12 is output.

Here, the radial support force is the radial support force caused by the support current IS and the radial support force caused by both the armature current IA and the support current IS (also referred to as the armature current IA in this specification). The sum of the radial bearing forces). Regarding the radial support force caused by both the armature current IA and the support current IS, when the d-axis component of the armature current IA (hereinafter referred to as the d-axis current) is increased, the radial support force increases, and when When the d-axis current is decreased, the radial support force decreases; when the absolute value of the q-axis component of the armature current IA (hereinafter referred to as the q-axis current) is increased, the radial support force increases, and when q This radial support force decreases as the absolute value of the shaft current decreases.

For example, in the steady operation region A, the control unit 60 controls the first power supply unit 61 (so-called maximum torque/current control) so that the armature windings 46a to 46c and 56a to 56c most efficiently generate torque with respect to the armature current IA , and the second power supply unit 62 is controlled so that a radial support force corresponding to the state of the turbo compressor 12 is output to the support windings 47a to 47c and 57a to 57c.

In addition, for example, in a region other than the steady operation region A, the control unit 60 controls the first power supply unit 61 and the second power supply unit 62 so that the armature windings 46 a to 46 c of the first bearingless motor 40 and the second bearingless motor 50 One of the voltage applied to the armature windings 56a to 56c, ie, the armature voltage VA, and the current flowing through the support windings 47a to 47c, 57a to 57c, ie, the support current IS, increases and the other decreases. Hereinafter, several examples of such control will be described.

[Strong magnetic flux control]

The control unit 60 performs the armature windings 46a to 46c, for example, in the turbulent flow region C and the surge region D where the load torque is relatively small and the radial load is large, when the operation of the turbo compressor 12 ends, and when the turbo compressor 12 is started. Strong magnetic flux control of 56a to 56c (ie, control to generate positive d-axis current).

Here, the control unit 60 increases the armature voltage command value to the first power supply unit 61 to increase the armature voltage VA in the first bearingless motor 40 and the second bearingless motor 50, and decreases the armature voltage VA for the second bearingless motor 40 and the second bearingless motor 50. The bearing current IS in the first bearingless motor 40 and the second bearingless motor 50 is reduced by the bearing voltage command value of the power supply unit 62 . The control unit 60 also controls the first power supply unit 61 and the second power supply unit 62 so that the bearing current IS in the first bearingless motor 40 and the second bearingless motor 50 does not exceed a predetermined first upper limit value (for example, by the second upper limit value). The power supply capacity of the power supply unit 62 is determined). As a result, the armature current IA, which is the current flowing in the armature windings 46a to 46c and 56a to 56c, can be increased without increasing the support current IS, thereby increasing the radial support force. Therefore, the power supply capacity of the second power supply unit 62 can be set relatively small with respect to the maximum radial support force that can be generated by the first bearingless motor 40 and the second bearingless motor 50 .

In addition, the control unit 60 may perform strong magnetic flux control by the first power supply unit 61 and control the strong magnetic flux by the second power supply unit 62, for example, when the temperatures of the support windings 47a to 47c and 57a to 57c reach a predetermined reference value or higher. Reduce the bearing current IS. Accordingly, while maintaining the radial support force, copper loss in the support windings 47a to 47c and 57a to 57c can be reduced, and an excessive temperature rise of the support windings 47a to 47c and 57a to 57c can be suppressed. As a result, the reliability of the turbo compressor 12 can be improved.

In addition, for example, when the rotation speeds of the first bearingless motor 40 and the second bearingless motor 50 are relatively small and the armature voltage VA is relatively small, the control unit 60 may generate a strong magnetic flux through the first power supply unit 61 . control, and the support current IS is reduced by the second power supply unit 62 . As a result, the armature voltage VA can be increased while maintaining the radial support force, and the control of the first bearingless motor 40 and the second bearingless motor 50 can be improved by improving the output accuracy of the armature voltage VA. sex.

In addition, when oil exists in the air gap between the rotor 41 and the stator 44 of the first bearingless motor 40 and between the rotor 51 and the stator 54 of the second bearingless motor 50, the control unit 60 may pass the first The first power supply unit 61 performs strong magnetic flux control, and the support current IS is reduced by the second power supply unit 62 . Thereby, the copper loss and iron loss in the armature windings 46a to 46c and 56a to 56c can be increased, and the oil in the air gap can be heated by the heat generation, and the viscosity of the oil can be lowered. As a result, the rotation losses of the first bearingless motor 40 and the second bearingless motor 50 can be reduced.

In addition, when the air conditioner 10 performs the heating operation, the control unit 60 may control the strong magnetic flux by the first power supply unit 61 and reduce the support current IS by the second power supply unit 62 . Thereby, the copper loss and iron loss in the armature windings 46a to 46c and 56a to 56c can be increased, and the refrigerant existing in the motor room S2 can be heated by the heat generation. The heat accumulated in the refrigerant by this heating is released to the air in the target space in the condenser 13 . Therefore, the heating capacity of the air conditioner 10 can be improved.

In addition, when the demagnetization resistance of the permanent magnets 43 of the first bearingless motor 40 and the permanent magnets 53 of the second bearingless motor 50 is small, the control unit 60 may perform strong magnetic flux control through the first power supply unit 61 . , and the support current IS is reduced by the second power supply unit 62 . Demagnetization of the permanent magnets 43 and 53 may occur due to the magnetic flux generated by the support current IS, but demagnetization is less likely to occur by performing such control. Therefore, since the permanent magnets 43 and 53 having a small coercive force can be used, the design freedom of the first bearingless motor 40 and the second bearingless motor 50 can be improved while reducing the cost.

[Weakening flux control]

For example, in the high-speed operation region, the control unit 60 performs the flux weakening control of the armature windings 46a to 46c and 56a to 56c (that is, control to generate a negative d-axis current). It should be noted that the high-speed operation region means that the armature voltage VA exceeds a predetermined second upper limit value (for example, determined by the power supply capacity of the first power supply unit 61 ) when the flux weakening control is not performed. The rotation speed of the rotation speed is the area where the operation is performed. In addition, the armature current IA increases when the flux-weakening control is performed compared to the case where the flux-weakening control is not performed.

Here, the control unit 60 increases the support voltage command value to the second power supply unit 62 to increase the support current IS in the first bearingless motor 40 and the second bearingless motor 50, and decreases the support voltage to the first power supply unit 62. The armature voltage VA in the first bearingless motor 40 and the second bearingless motor 50 is reduced by the armature voltage command value of 61. Further, the control unit 60 controls the first power supply unit 61 and the second power supply unit 62 so that the armature voltage VA in the first bearingless motor 40 and the second bearingless motor 50 does not exceed the second upper limit value. Thereby, the turbo compressor 12 can be operated in the high-speed operation region without increasing the armature voltage VA, and the decrease in the radial support force accompanying the flux weakening control can be compensated for by the increase in the support current IS. Therefore, the power supply capacity of the first power supply unit 61 can be set relatively small with respect to the width of the high-speed operation region of the turbo compressor 12 .

In addition, the control unit 60 may perform the flux weakening control when the turbo compressor 12 is activated, for example. When the turbo compressor 12 is started, the drive shaft 31 is supported by the first bottoming bearing 71 and the second bottoming bearing 72 . Therefore, when the permanent magnets 43 and 53 of the first bearingless motor 40 and the second bearingless motor 50 When a relatively large radial support force is required, the weak magnetic flux control seems to reduce the magnetic force of the permanent magnets 43 and 53 and reduce the required radial support force. Therefore, the controllability of the first bearingless motor 40 and the second bearingless motor 50 can be improved.

In addition, when oil exists in the air gap between the rotor 41 and the stator 44 in the first bearingless motor 40 and in the air gap between the rotor 51 and the stator 54 in the second bearingless motor 50, the control unit 60 It is also possible to perform flux weakening control and to increase the support current IS. Thereby, the copper loss in the support windings 47a to 47c and 57a to 57c can be increased, and the oil in the air gap can be heated by the heat generation, and the viscosity of the oil can be lowered. As a result, the rotation losses of the first bearingless motor 40 and the second bearingless motor 50 can be reduced.

In addition, when the air conditioner 10 performs the heating operation, the control unit 60 may perform the flux weakening control and increase the support current IS. Thereby, the copper loss in the support coils 47a to 47c and 57a to 57c can be increased, and the refrigerant existing in the motor room S2 can be heated by the heat generation. The heat accumulated in the refrigerant by this heating is released to the air in the target space in the condenser 13 . Therefore, the heating capacity of the air conditioner 10 can be improved.

[Regeneration Control]

For example, the control unit 60 performs regeneration control (ie, control for generating a negative q-axis current) at the end of the operation in which the radial load becomes large.

Here, the control unit 60 increases the armature voltage command value to the first power supply unit 61 to increase the armature voltage VA in the first bearingless motor 40 and the second bearingless motor 50, and decreases the armature voltage VA for the second bearingless motor 40 and the second bearingless motor 50. The bearing current IS in the first bearingless motor 40 and the second bearingless motor 50 is reduced by the bearing voltage command value of the power supply unit 62 . Further, the control unit 60 controls the first power supply unit 61 and the second power supply unit 62 so that the bearing current IS in the first bearingless motor 40 and the second bearingless motor 50 does not exceed the first upper limit value. Thereby, the armature current IA can be increased without increasing the support current IS, and the radial support force can be increased. Therefore, the power supply capacity of the second power supply unit 62 can be set relatively small with respect to the maximum radial support force that can be generated by the first bearingless motor 40 and the second bearingless motor 50 . In addition, by regenerating the rotational energy, energy saving of the turbo compressor 12 can be achieved, and the time for stopping the rotation can be shortened.

In addition, when the radial load suddenly increases when the first bearingless motor 40 and the second bearingless motor 50 are controlled while generating a positive q-axis current by the first power supply unit 61, the control unit 60 may Regenerative control in which a negative q-axis current whose absolute value is larger than the positive q-axis current is generated. Accordingly, the radial support force can be increased without increasing the support current IS by the second power supply unit 62 . It should be noted that it is also conceivable to increase the absolute value of the positive q-axis current without reversing the polarity, and to obtain the same effect.

-Effect of Embodiment-

The motor system 30 of the present embodiment includes: a drive shaft 31 that drives the load bearing 21 to rotate; a first bearingless motor 40 and a second bearingless motor 50 having rotors 41 and 51, respectively, and armature windings 46a to 46c, 56a to 56c and the stators 44 and 54 supporting the windings 47a to 47c and 57a to 57c drive the drive shaft 31 to rotate and support the radial load of the drive shaft 31 in a non-contact manner; The armature windings 46a to 46c and 56a to 56c apply voltage; the second power supply unit 62 applies voltage to the support windings 47a to 47c and 57a to 57c; and the control unit 60 controls the first power supply unit 61 and the The second power supply unit 62 increases one of the armature voltage VA and the support current IS, which is a voltage applied to the above-mentioned armature windings 46a to 46c and 56a to 56c, and decreases the other, The support current IS is a current flowing through the support windings 47a to 47c and 57a to 57c described above.

Therefore, by increasing one of the armature voltage VA and the bearing current IS and decreasing the other, the first power supply unit 61 and the second power supply can be adjusted according to the operating conditions of various devices using the motor system 30 . The armature voltage VA and the bearing current IS are adjusted within the range of the power supply capacity of each part 62 . That is, when the power supply capacities of the first power supply unit 61 and the second power supply unit 62 are limited, respectively, in order to obtain desired outputs from the first bearingless motor 40 and the second bearingless motor 50, the power supply units 61 and 62 are When the power supply capacity of one of them is insufficient, the shortage can be compensated by the power supply units 61 and 62 of the other.

Further, in the motor system 30 of the present embodiment, the control unit 60 controls the first power supply unit 61 and the second power supply unit 62 such that the armature voltage VA increases and the bearing current IS decreases, or the bearing The current IS increases and the aforementioned armature voltage VA decreases. When such control is employed, the operating area of the motor system 30 can be widened.

Further, in the motor system 30 of the present embodiment, the control unit 60 controls the first power supply unit 61 and the second power supply unit 62 so that the armature voltage VA increases and the support current IS does not exceed a predetermined first upper limit. Therefore, the support current IS can be kept from exceeding the first upper limit value, while the radial support force caused by the armature current IA, which is a current flowing through the armature windings 46a to 46c and 56a to 56c, can be increased. This corresponds to, for example, the case where the strong magnetic flux is controlled by the first power supply unit 61 . This is particularly effective when the radial support force is increased in a state where the support current IS reaches the first upper limit value or a value near the first upper limit value.

In addition, in the motor system 30 of the present embodiment, the control unit 60 controls the first power supply unit 61 and the second power supply unit 62 so that the bearing current IS increases and the armature voltage VA does not exceed a predetermined second upper limit. Therefore, the armature voltage VA may not exceed the second upper limit value. However, for example, when the rotational speeds of the first bearingless motor 40 and the second bearingless motor 50 are increased, the radial support force caused by the armature current IA has may decline. This case corresponds to, for example, the case where the flux weakening control is performed by the first power supply unit 61 . On the other hand, the support current IS can be increased by the second power supply unit 62, and the decrease can be compensated for by the radial support force caused by the support current IS.

Further, in the motor system 30 of the present embodiment, the control unit 60 controls the first power supply unit 61 and the second power supply unit 62 so that the armature voltage VA decreases and the support current IS increases, or the support The current IS decreases and the aforementioned armature voltage VA increases. When such control is employed, for example, heat generation in the armature windings 46a to 46c and 56a to 56c or the support windings 47a to 47c and 57a to 57c can be utilized as necessary.

Further, in the motor system 30 of the present embodiment, the control unit 60 controls the first power supply unit 61 and the second power supply unit 62 so that the armature voltage VA decreases and the support current IS exceeds a predetermined first lower limit value. Therefore, the support current IS can exceed the first lower limit value. Thereby, for example, the heat generated in the support windings 47a to 47c and 57a to 57c can be utilized as needed, or the detection accuracy of the support current IS can be improved to improve the performance of the first bearingless motor 40 and the second bearingless motor 50 . of control.

Further, in the motor system 30 of the present embodiment, the control unit 60 controls the first power supply unit 61 and the second power supply unit 62 so that the bearing current IS decreases and the armature voltage VA exceeds a predetermined second lower limit value. Therefore, the armature voltage VA can exceed the second lower limit value. Thereby, for example, the heat generation in the armature windings 46a to 46c and 56a to 56c can be used as necessary, or the output accuracy of the armature voltage VA can be improved to improve the performance of the first bearingless motor 40 and the second bearingless motor 50. control.

Further, the turbo compressor 12 of the present embodiment includes the motor system 30 of the present embodiment, and the impeller 21 which is connected to the drive shaft 31 of the motor system 30 and serves as the load 21 . Therefore, in the turbo compressor 12 , the impeller 21 is driven to rotate by the first bearingless motor 40 and the second bearingless motor 50 .

In addition, the turbo compressor 12 of the present embodiment is provided in the refrigerant circuit 11 that performs the refrigeration cycle, and is configured so that the refrigerant is compressed by the impeller 21, and the turbo compressor 12 is caused to rotate in the region C or the surge region where the rotational stall occurs. When D is operating, the control unit 60 controls the first power supply unit 61 and the second power supply unit 62 so that the armature voltage VA increases and the support current IS does not exceed a predetermined first upper limit value. Therefore, when the load torque of the first bearingless motor 40 and the second bearingless motor 50 is small and the required radial supporting force is large, the radial supporting force caused by the armature current IA can be increased. . Therefore, even if the support current IS is suppressed to be equal to or less than the first upper limit value, the increase in the armature current IA can increase the radial support force of the first bearingless motor 40 and the second bearingless motor 50 .

(Other Embodiments)

The above-described embodiment may adopt the following configurations.

For example, the motor system 30 may have only one bearingless motor, or may have three or more bearingless motors. Here, in the former case, the motor system 30 preferably has radial magnetic bearings.

In addition, the types of the first bearingless motor 40 and the second bearingless motor 50 are not limited to the commutation pole type. For example, a surface magnet type (SPM: Surface Permanent Magnet) in which permanent magnets are attached to the surface of the rotor may be used. The interior of the rotor is an embedded magnet type (IPM: Interior Permanent Magnet), an insertion type, a BPM (Buried Permanent Magnet) type, a positive salient pole type, etc., in which a permanent magnet is embedded. In addition, the types of the two bearingless motors 40 and 50 may be different from each other. In addition, each bearingless motor 40 and 50 may be a bearingless motor in which the d-axis self-inductance and q-axis self-inductance of the armature are substantially equal and do not have saliency, and the d-axis self-inductance of the armature is smaller than the q-axis self-inductance. In addition, any of a bearingless motor having a reverse saliency and a bearingless motor having a positive saliency and a d-axis self-inductance of the armature larger than the q-axis self-inductance. Here, as the bearingless motor having no saliency polarity, there are reversing pole type, surface magnet type, etc.; as the bearingless motor having reverse saliency polarity, there can be mentioned the built-in magnet type, the plug-in type, and the BPM type. etc. As a bearingless motor having a positive saliency, a positive saliency type etc. can be mentioned.

In addition, the number of the impellers 21 included in the turbo compressor 12 may be two or more, for example, one impeller 21 may be installed on each of both ends of the drive shaft 31 .

In addition, the control method of the first power supply unit 61 in the steady operation region A may be a method other than the maximum torque/current control, for example, maximum efficiency control (control to minimize loss) and control with a power factor of 1 may be used. (Control to make the power factor substantially 1).

It should be noted that, of course, the application of the motor system 30 is not limited to the turbo compressor 12 .

As mentioned above, although embodiment and modification were described, it is understood that various changes can be made to the aspect and the specific situation without departing from the spirit and scope of the claims. In addition, as long as the functions of the objects of the present invention are not affected, the above-described embodiments and modifications may be appropriately combined or replaced.

－Industrial Applicability－

As described above, the present invention is useful for an electric motor system and a turbo compressor provided with the electric motor system.

-Symbol Description-

11 Refrigerant circuit

12 Turbo compressor

21 Impeller (load)

30 Motor system

31 Drive shaft

40 The first bearingless motor (bearingless motor)

41 Rotor

46a～46c Armature winding

47a～47c Support winding

50 Second bearingless motor (bearingless motor)

51 Rotor

56a～56c Armature winding

57a～57c Support winding

60 Control Department

61 The first power supply unit (power supply unit)

62 Second power supply unit (power supply unit)

Claims (9)

1. An electric motor system, comprising:

a drive shaft (31) that rotationally drives the load (21);

bearingless motors (40, 50) each having a rotor (41, 51) and a stator (44, 54) provided with armature windings (46a to 46c, 56a to 56c) and support windings (47a to 47c, 57a to 57c), and configured to rotationally drive the drive shaft (31) and contactlessly support a radial load of the drive shaft (31);

power supply units (61, 62) for applying voltages to the armature windings (46a to 46c, 56a to 56c) and the support windings (47a to 47c, 57a to 57c), respectively; and

and a control unit (60) that controls the power supply units (61, 62) such that one of an armature voltage VA that IS a voltage applied to the armature windings (46a to 46c, 56a to 56c) and a support current IS that IS a current flowing through the support windings (47a to 47c, 57a to 57c) IS increased and the other IS decreased.

2. The motor system of claim 1,

the control unit (60) controls the power supply units (61, 62) such that the armature voltage VA increases and the support current IS decreases, or such that the support current IS increases and the armature voltage VA decreases.

3. The motor system according to claim 1 or 2,

the control unit (60) controls the power supply units (61, 62) such that the armature voltage VA increases and the support current IS does not exceed a predetermined first upper limit value.

4. The motor system according to any one of claims 1 to 3,

the control unit (60) controls the power supply units (61, 62) such that the support current IS increases and the armature voltage VA does not exceed a predetermined second upper limit value.

5. The motor system according to any one of claims 1 to 4,

the control unit (60) controls the power supply units (61, 62) such that the armature voltage VA decreases and the support current IS increases, or such that the support current IS decreases and the armature voltage VA increases.

6. The motor system according to any one of claims 1 to 5,

the control unit (60) controls the power supply units (61, 62) such that the armature voltage VA decreases and the support current IS exceeds a predetermined first lower limit value.

7. The motor system according to any one of claims 1 to 6,

the control unit (60) controls the power supply units (61, 62) such that the support current IS decreases and the armature voltage VA exceeds a predetermined second lower limit value.

8. A turbocompressor, characterized in that it comprises:

the electric motor system (30) of any one of claims 1 to 7; and

and an impeller (21) connected to the drive shaft (31) of the motor system (30) and serving as the load (21).

9. The turbocompressor according to claim 8,

the turbo compressor (12) is provided in a refrigerant circuit (11) that performs a refrigeration cycle and configured to compress a refrigerant by the impeller (21),

when the turbo compressor (12) IS operated in a region (C) or a surge region (D) where rotating stall occurs, the control unit (60) controls the power supply units (61, 62) so that the armature voltage VA increases and the support current IS does not exceed a predetermined first upper limit value.

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