RU2237345C2 - Two-engine electric drive - Google Patents

Abstract

FIELD: electric engineering.

SUBSTANCE: device has two asynchronous engines, into rotor circuit of which rectifiers are switched, anode groups of which are comprised of diodes, and cathode - of thyristors, connected to each other in parallel. In series to these connected are inverter with constant output frequency, powering rectifier, and smoothing reactor. To inverter output windings of both engines stators are connected. Control electrodes of rectifiers thyristors are connected to rotor windings of respective engines through two diode groups and resistor with controlled resistance.

EFFECT: simplified construction, increased reliability, possible adjustment of angular speed of engines while returning sliding energy into circuit of engines stator windings, synchronized angular speeds of engines.

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Description

The invention relates to electrical engineering and can be used in electric drives of production mechanisms, where the engines operate at a common load, for example on hoisting-and-transport mechanisms.

Known AC electric drive containing two induction motors, a thyristor switch in the winding circuit of the stators of electric motors, a series-connected comparison unit, an amplifier and a pulse-phase control unit, the output of which is connected to the input of the thyristor switch, a reference unit, two speed sensors, each of which is installed on the shaft of the corresponding electric motor, a pulse generator, a switch whose input is connected to the output of the speed sensors, and the output of which is connected to about the input of the comparison unit [1]. The disadvantage of this device is its complexity, since it is necessary to install speed sensors, rotation sensors, a pulse generator and a control system for aligning engine speeds.

Closest to the proposed one is a twin-motor drive containing two induction motors with a phase rotor, two unregulated bridge rectifiers, the input of the first rectifier connected to the rotor windings of the first motor, and the input of the second rectifier connected to the rotor windings of the second motor, unregulated bridge rectifiers connected together in parallel moreover, the positive output of the first rectifier is connected to the positive output of the second rectifier, and the negative output of the first It is connected to the negative output of the second rectifier, the positive input of the inverter is connected to the positive outputs of unregulated rectifiers, the output of which is connected to the motor stators windings connected in parallel, and the negative input of the inverter is connected through the smoothing reactor to the negative output of the supply rectifier, and the positive output of the supply rectifier is connected to negative outputs of unregulated rectifiers, the power input of the supply rectifier is connected to the network, and its control input is It is connected to the output voltage control device, the inverter is autonomous, its control unit is connected to the output frequency control device.

The disadvantage of this device is its complexity, since to control the engine speed it is necessary to simultaneously change the frequency at the inverter output and the voltage at the output of the supply rectifier using the inverter and rectifier control units, which requires the use of a two-channel control system.

The proposed twin-motor drive contains two induction motors with a phase rotor, two three-phase bridge rectifiers, the input of the first bridge rectifier connected to the rotor windings of the first motor, and the input of the second bridge rectifier connected to the rotor windings of the second motor, another third rectifier, the input of which is connected to the power supply network, three-phase inverter, the output of which is connected to the windings of the stators of the motors connected in parallel, the first two bridge rectifiers are interconnected pa allele, moreover, the positive output of the first rectifier is connected to the positive output of the second rectifier, and the negative output of the first rectifier is connected to the negative output of the second rectifier, the positive input of these two rectifiers is connected to the positive input of the three-phase inverter, the negative input of which is connected to the negative output of the third rectifier, the positive input which is connected to one terminal of the winding of the smoothing reactor, the other terminal of the winding of which is connected to negative the outputs of two parallel-connected bridge rectifiers, in which the gates that make up the rectifier's negative output groups are made of diodes, and the gates that make up the rectifier's positive output groups are made of thyristors, the cathode of one of the six protective circuits is connected to the control input of each of the six thyristors of these two rectifiers diodes, the anodes of which are connected to a common point and connected to one terminal of an adjustable resistor, to the other terminal of which are connected the cathodes of other These are diodes, the anode of the first of these diodes is connected to the first phase of the rotor winding of the first motor, the anode of the second diode is connected to the second phase of the rotor winding of the first motor, the anode of the third diode is connected to the third phase of the rotor winding of the first motor, the anode of the fourth diode is connected to the first phase of the rotor winding of the second motor, the anode of the fifth diode is connected to the second phase of the rotor winding of the second engine, and the anode of the sixth diode is connected to the third phase of the rotor winding of the second motor, to the common point of connection of the positive outputs of the first the second and second bridge rectifiers connected to the cathode of the additional diode, the anode of which is connected to the common point of connection of the negative outputs of the first and second bridge rectifiers.

In this two-motor electric drive, the engine speeds are controlled by changing the resistance value of the control resistor, while synchronizing the speed of the engines. The electric drive has a simple design and high reliability.

Figure 1 shows the electrical circuit of the device, figure 2 - experimental mechanical characteristics.

The twin-motor drive contains two induction motors 1 and 2, the ends of the windings of the rotors of the motors are connected to the inputs of the bridge rectifiers 3 and 4, connected in parallel so that the positive output of the rectifier 3 is connected to the positive output of the rectifier 4 to a common point 5, and the negative output of the rectifier 3 is connected to negative output of rectifier 4 to common point 6, rectifier 3 has a group of valves 7 connected to common point 5 of positive output of rectifiers 3 and 4 made of thyristors, same rectifier 3 has a group of veins Ilei 8, connected to the common point 6 of the negative output of rectifiers 3 and 4, is made of diodes, rectifiers 4 have a valve group 9, connected to a common point 5 of the positive output of rectifiers 3 and 4, is made of thyristors, for the same rectifier 4 group of valves 10 connected to the common point 6 of the negative output of the rectifiers 3 and 4, is made of diodes. A positive terminal from the input of a three-phase inverter 11 is connected to a common point 5 of the positive output of rectifiers 3 and 4, a negative terminal from the input of which is connected to a negative terminal from the output of rectifier 12, a terminal from the positive output of which is connected to the first terminal of the smoothing reactor winding 13, and the second terminal of the winding which is connected to a common point 6 of the connection of the rectifiers 3 and 4, the three-phase output of the inverter 11 is connected to the parallel-connected three-phase windings of the stators of the motors 1 and 2, the input of the rectifier 12 is connected en to the mains. The cathode of one of the six protective diodes 14 is connected to the control electrode of the thyristors 7 of the rectifier 3 and the thyristors 9 of the rectifier 4, the anodes of which are connected to a common point 15, to which one terminal of an adjustable resistor 16 is connected, the other terminal of which is connected to a common point 17, which also the cathodes of three diodes 18, 19, 20 and three more diodes 21, 22, 23 are connected, the anode of the diode 18 is connected to the first phase of the rotor winding of the motor 1, the anode of the diode 19 is connected to the second phase of the rotor winding of the motor 1, the anode of the diode 20 is connected to the third phase motor rotor windings 1, the anode of the diode 21 is connected to the first phase of the winding of the rotor of the motor 2, the anode of the diode 22 is connected to the second phase of the winding of the rotor of the motor 2, the anode of the diode 23 is connected to the third phase of the winding of the rotor of the motor 2. A diode cathode is connected to the common point 5 of the connection of the rectifiers 3 and 4 24, and to the common point 6 of the connection of the rectifiers 3 and 4, the anode of the diode 24 is connected.

A twin-engine electric drive operates as follows. When the rectifier 12 is turned on, the supply voltage is supplied through the reactor 13 and the diode 24 to the input of the inverter 11, when turned on, the voltage from its output is supplied to the parallel connected windings of the stators of the motors. EMF is induced in the windings of the rotors of engines 1, 2. The voltage from the terminals of the windings of the rotor of the motor 1 through the diodes 18-20, the resistor 16 and the protective diodes 14 is supplied to the control electrodes of the group of thyristors 7 of the rectifier 3, and the voltage from the terminals of the windings of the rotors of the motor 2 through the diodes 21-23, the resistor 16 and the protective diodes 14 to the control electrodes of the group of thyristors 9 of the rectifier 4. The groups of thyristors 7 and 9 open, and the voltage from the outputs of the rectifiers 3 and 4 is added to the voltage at the output of the rectifier 12 and this total voltage is applied to the input of the inverter 11.

The inverter 11 is the source of the back EMF of Eu, introduced into the circuit of the rotors of the motors 1 and 2. However, the sum of the voltage of the rectifier 12 Ud and the rectified EM of the rotors of the motors E _2d * S, proportional to the slip S, is greater than the EMF of the inverter Eu, which determines the current flow in the rectified circuit id:

where R _E is the equivalent total resistance of all elements, reduced to a straightened circuit;

ΔU _вΣ is the total voltage drop across the valves of the circuit.

. Если, например, двигатель 1 обогнал двигатель 2, его скольжение уменьшается S₁<S₂, тогда

, и мостовой выпрямитель 4 подпирает мостовой выпрямитель 3. В результате эквивалентная противоЭДС в цепи ротора двигателя 1 становится больше, чем эквивалентная противоЭДС в цепи ротора двигателя 2, поэтому двигатель 1 подтормаживается и скорости двигателей выравниваются. Таким образом, в электроприводе осуществляется синхронизация скоростей двигателей.When the speeds are equal and the motors EMF slip, their rotor windings are equal to each other

. If, for example, engine 1 overtakes engine 2, its slip decreases S ₁ <S ₂ , then

, and the bridge rectifier 4 supports the bridge rectifier 3. As a result, the equivalent counter-EMF in the rotor circuit of the engine 1 becomes larger than the equivalent counter-EMF in the rotor circuit of the engine 2, so the engine 1 is braked and the speed of the motors are equalized. Thus, in the electric drive, the synchronization of engine speeds is carried out.

In this electric drive, the windings of the stators and rotors of engines 1 and 2 are connected to a common electric circuit using a DC link, and the slip energy of the motors is transferred from the rotor chains of the motors directly to the windings of their stators, providing the drive with high energy performance. The supply rectifier 12 may be uncontrolled, made of diodes, in this case, the voltage at its output Udo will have a constant value Udo = const. In figure 2, line 1 shows the mechanical characteristic under the condition Udo = const and Ry _min , that is, the resistance of the resistor 16 has a minimum value. In this case, the thyristor groups 7 of the rectifier 3 at any speed of the motors 1 and 2 receive a control signal from the windings of the rotors of the motors, sufficient to open them, i.e. work in diode mode.

и

возрастают, следовательно, возрастает ток управления группами тиристоров выпрямителей 3 и 4. В точке Б на линии 2 (см. фиг.2) тиристоры выпрямителей 3 и 4 будут открытыми и двигатели 1 и 2 будут работать при установившейся скорости вращения. При изменении нагрузки на валах двигателей 1 и 2 при постоянном значении сопротивления Ry резистора 16 двигатели будут работать на механической характеристике, показанной на фиг.2 линией 2. При дальнейшем увеличении сопротивления Ry резистора 16 двигатели 1 и 2 перейдут на механическую характеристику с меньшей скоростью W₂, показанной на фиг.2 линией 3. При еще большем увеличении сопротивления Ry резистора 16 двигатели 1 и 2 перейдут на механическую характеристику, показанную на фиг.2 линией 4 и т.д. Таким образом, установившуюся частоту вращения двигателей 1 и 2 регулируют путем изменения сопротивления Ry резистора 16.With increasing resistance Ry of the resistor 16, the voltage drop from the control current of the groups of thyristors 7 of the rectifier 3 and the thyristors 9 of the rectifier 4 increases on it. The control current of the groups 7 and 9 of the thyristors decreases. If the motors worked at point A on line 1 (see Fig. 2), then with an increase in resistance Ry, the thyristors of group 7 of rectifier 3 and group 9 of rectifier 4 receive a control current insufficient to open them, so these thyristors will be in a closed state. The rotor currents of the engines 1 and 2 are interrupted, the motors are braked to a speed of W ₁ , while the slip S ₁ and S _{2 of the} motors increase, the EMF of the rotors of the engines

and

therefore, the control current of the groups of thyristors of rectifiers 3 and 4 increases. At point B on line 2 (see FIG. 2), the thyristors of rectifiers 3 and 4 will be open and motors 1 and 2 will work at a steady rotation speed. When the load on the shafts of the engines 1 and 2 changes with a constant value of the resistance Ry of the resistor 16, the motors will operate on the mechanical characteristic shown in Fig. 2 by line 2. With a further increase in the resistance Ry of the resistor 16, the motors 1 and 2 will switch to the mechanical characteristic with a lower speed W ₂ , shown in FIG. 2 by line 3. With an even greater increase in the resistance Ry of resistor 16, motors 1 and 2 will switch to the mechanical characteristic shown in FIG. 2 by line 4, etc. Thus, the steady-state speed of the motors 1 and 2 is controlled by changing the resistance Ry of the resistor 16.

In this device, the inverter 11 provides only one frequency of the output voltage equal to the rated frequency of the motors, which greatly simplifies the design of the inverter, reduces its cost and increases reliability. The supply rectifier 12 can be unregulated, made of diodes, which simplifies its design, reduces its cost and increases reliability.

Thus, the twin-motor drive has a simple and reliable system for controlling the angular speed of motors down from the main speed with a control range of up to 10: 1, while the sliding energy from the rotor winding is returned to the stator winding, which ensures the economical operation of the electric drive at any angular speed of the motor. In addition, in a twin-engine electric drive, the synchronization of the angular speeds of the engines is provided.

Literary sources

1. USSR author's certificate No. 904171, MKI N 02 P 5/46, 13.06.80.

2. RF patent No. 2160495. Twin-engine electric drive, V. N. Meshcheryakov, V. V. Fedorov, D. S. Osipov, MKI N 02 P 7/74, 10.12.2000, bull. Number 34.

Claims (1)

A two-motor electric drive containing two induction motors with a phase rotor, two three-phase bridge rectifiers, the input of the first bridge rectifier connected to the rotor windings of the first motor, and the input of the second bridge rectifier connected to the rotor windings of the second motor, the third rectifier, the input of which is connected to the mains, a three-phase inverter, the output of which is connected to the windings of the stators of the motors connected in parallel, the first two bridge rectifiers are connected together in parallel, and the negative output of the first rectifier is connected to the positive output of the second rectifier, and the negative output of the first rectifier is connected to the negative output of the second rectifier, the positive input of the three-phase inverter is connected to the positive outputs of which the negative input is connected to the negative output of the third rectifier, the positive input of which is connected to one terminal of the winding of the smoothing reactor, the other terminal of the winding of which is connected to the negative terminals of two parallel flax-connected bridge rectifiers, characterized in that for two parallel-connected bridge rectifiers, the gates making up the negative output groups of the rectifier are made of diodes, and the gates making up the positive output groups of the rectifier are made of thyristors to the control electrode of each of the six thyristors of these two rectifiers the cathode of one of the six protective diodes is connected, the anodes of which are connected to a common point and connected to one terminal of an adjustable resistor, to the other terminal of which cathodes of the other six diodes are connected to a common point, the anode of the first of these diodes is connected to the first phase of the rotor winding of the first motor, the anode of the second diode is connected to the second phase of the rotor winding of the first motor, the anode of the third diode is connected to the third phase of the rotor winding of the first motor, the anode of the fourth the diode is connected to the first phase of the rotor winding of the second motor, the anode of the fifth diode is connected to the second phase of the rotor winding of the second motor, and the anode of the sixth diode is connected to the third phase of the rotor winding of the second motor, the common point of connection of the positive outputs of the first and second bridge rectifiers connected to the cathode of the additional diode, the anode of which is connected to a common point of connection of the negative outputs of the first and second bridge rectifiers.

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