JPS63206186A - Protective device of brushless dc motor - Google Patents

Abstract

PURPOSE:To prevent a motor against the destruction of parts, by detecting whether the motor is rotating by external force and whether it is generating the current, and by connecting armature winding to a motor drive circuit only when the current is smaller than a definite value. CONSTITUTION:In a brushless DC motor, the position of a rotor 1 is detected with a phase detection device 2, by which position signal the current direction to cause the current to flow from a DC power source 5 to a stator armature winding 4 with a motor drive control device 13 is changed over by driving a transistor 6 to rotate the rotor 1. A relay 11 is provided for the changeover means to change over the armature winding 4 from a motor drive circuit 8 to a resistance 12 to connect. This relay 11 is excited with the abovementioned control device 13 and connects the armature winding 4 to the motor drive circuit 8. The winding current is detected by a current detection device 14. In case the detected current value is larger than the set current value, a current value processing device 16 is provided to output the current large signal to the control device 13. The destruction of semiconductor parts by the short-circuit current is thereby prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a protection device for a brushless DC motor used in an outdoor V1 of an air conditioner.

BACKGROUND OF THE INVENTION A brushless DC motor conventionally used in this type of air conditioner generally has a drive circuit as shown in FIG. In FIG. 4, 1 is a rotor with v11+IiA of a brushless DC motor to which a fan (Zeza shown in the figure) of an air conditioner outdoor unit is directly connected, and the position of rotor 1 is detected by a phase detection device 2. . Upon receiving the driving command, the motor drive control device 3 drives the transistor 6 to change the direction of the current flowing from the DC power supply 5 to the dielectric winding FiJ4 of the motor stator based on the position of the rotor 1 detected by the phase detection device 2. Then, the rotor 1 is rotated by forming magnetic poles in the stator that are opposite 5t to mt of the rotor 1.

Reference numeral 7 denotes a diode for protecting the transistor, which together with the DC power supply 5 iJ3 and the transistor 6 forms a first circuit 8 in the 11th section. Note that 9 is a breaker that cuts off the current flowing through the armature valley wire 4.

Problems to be Solved by the Invention Since the outdoor unit of an air conditioner is installed in a well-ventilated location, it is often exposed to natural wind directly. Therefore, the natural wind may cause the outdoor unit's fan mechanism to rotate, or the solar insulated direct current motor connected directly to the fan to rotate.

If the motor is rotating naturally in the positive direction by applying the external force of the natural wind, 3 is 7-ri 1. Suppose that Qu 1 and QL 2 of the transistor 6 are turned on, and everything else is turned off.At this point, the voltage Vl-24 generated between Ml and M2 of the armature winding 4 is the armature'. 11/l M
The voltage is supplied to the DC power supply 5 side through Du1 of the die door, with the 1 side being Φ and the M2 side being O. As mentioned above, when the motor is rotating in the forward direction due to natural wind, the voltage rise alone is not a big problem, but at this same moment, the motor is rotating in the opposite direction due to natural wind. If so, the generated tu cat Vt
-2 is the opposite voltage ((+) and (-) in Figure 4),
As shown by the broken line C in FIG. 4, a short-circuit current flows from QL2/J of transistor 6 to DL1 of the diode, and at the same time, as shown by the solid line, a short-circuit current flows from DL2 of diode 7 to Qu1 of transistor 6. ! r8m F flows.

Furthermore, when the external force to which the fan is subjected increases, the number of rotations increases during times such as typhoons, and when the fan rotates in the opposite direction, the short-circuit current increases, causing serious problems such as destroying semiconductor components such as the transistor 6 and the diode 7. There was a problem.

The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a brushless DC motor protection device that can prevent damage to the semiconductor components constituting the motor drive circuit 8.

Means for Solving the Problems In order to solve the above problems, the present invention provides an arrangement in which the armature winding of a brushless DC motor is switched and connected to a motor drive circuit and a resistance circuit in which the armature winding forms a closed circuit. a current detecting device that detects a current flowing from the electronic α-element winding to the resistor circuit; and an output of the current detecting device is pan-nosed, and when the detected output is below a certain value, the switching device is configured to The motor is equipped with a motor drive V control device that drives the armature winding and connects the armature winding to the motor drive circuit side.

Effect With the above configuration, before the brushless DC motor starts driving, the armature winding is connected to the resistance circuit side by the switching means. When the motor is being rotated by an external force such as natural wind, the resistance is A current is flowing through. This current is detected by a current detection device to detect whether or not the remoter is rotating due to an external force and lightning is occurring, and only when the detection output of the current detection device is below a certain value, the armature is switched off by a switching device. By connecting the winding to the motor drive circuit side, when the current generated by the external force flows to the semiconductor component of the motor drive circuit as a short-circuit current, the semiconductor component is prevented from being destroyed.

EXAMPLE Hereinafter, an example of the present invention will be explained based on FIGS. 1, 2, and 3.

FIG. 1 is a circuit diagram of a brushless DC motor using the brushless DC motor protection device of the present invention. Components having the same functions as those of the conventional example are given the same reference numerals and their explanations will be omitted.

In FIG. 1, a relay 11 is a switching means for switching and connecting the armature winding 4 to the motor drive circuit 8 and the resistor 12. When the relay 11 is excited by the motor drive control device 13, the armature winding 4 is connected to the motor drive circuit 8. When the relay 11 is not energized, that is, before the motor starts driving, the armature winding 4 and the resistor 12 form a closed circuit. 14 is a current detection Vt position that detects the armature winding current flowing in the fi 43 child winding 4, and a current detector (hereinafter referred to as CT) 15 that detects the armature winding current;
The current value processing device 16 is connected to T15 and outputs a large current signal to the motor drive control device 13 when the armature @ line current is larger than the set current value 1c.

Current value place 1! I! The set current value 1c of the device 16 is set as follows. As shown in FIG. 2, when the brushless DC motor is rotating at the rated rotation speed nN during normal operation, the current value flowing through the electric prewinding 84 is IN, and the brushless DC motor directly connected to the fan is rotating in reverse. When the relay 11 is energized and the transistor 6 is driven, the armature winding 4, the transistor 6, and the diode 7 are short-circuited and a short-circuit current flows, which destroys semiconductor components such as the transistor 6 and the diode 7. If the current value is 18, the 1c is set between IN and 1 day. The short circuit current value is proportional to the reverse rotation speed of the brushless DC motor due to natural wind.

The motor drive control device 13 is operated by a driving command signal,
Based on the signal from the current value processing device 16, the following operation is performed according to the flowchart shown in FIG. The motor drive control device 13 starts with the current value processor 3! l! device 16
Check whether a current signal is input from the relay 11).If a large current signal is not input, that is, if the current value flowing through the armature winding 4 is below a certain value, the relay 11 is excited to connect the armature winding 4 to the motor drive circuit 8 (step 22), and drive the transistor 6 to start normal operation (step 23). If a large current signal is input, all transistors 6
In step 24), the motor drive circuit 8 is not driven and the relay 11 is not energized, and the resistor 12 is connected to the electric coil 4 (step 24), and then the process is waited for a certain period of time (step 25). ), again at the end of standby (step 21)
Return to , and check if a large current signal is being input.

In this way, when starting motor drive, it is checked whether the armature current value is larger than the set current value, and if there are no people, that is, if the current value is less than the set current value, the armature winding 4 is connected to the side of the motor drive circuit 8. By repeatedly stopping the motor drive for a certain period of time and waiting when the voltage is large, the current generated in the motor by the external force flows through the motor drive circuit 8 as a short F6 current, and the transistor 6 and diode It is possible to prevent semiconductor components such as 7 from being destroyed.

In this embodiment, the current value processing device 16 determines whether the armature current value is equal to or higher than the set current value, but the function of the current value processing device 16 is simply to output a signal of the armature current value. It is also possible to input a signal of the armature current value to the motor drive control device 13 to determine whether the M current value is greater than or equal to the set M current value.

Effects of the Invention As described above, according to the present invention, the armature winding is connected to the motor drive circuit by the switching means only when the current value flowing through the armature winding at the start of motor drive is below a certain value. Therefore, the current that is generated when the motor rotates naturally due to external forces such as wind and flows into the armature winding, and a large current exceeding a certain value flows through the motor drive circuit as a short-circuit current, causing the motor to drive. It is possible to prevent damage to the semiconductor components of the circuit. Therefore, when a brushless DC motor protection device is used in a product that is installed outdoors, such as an outdoor unit of an air conditioner, the motor drive circuit can be reliably protected in abnormal conditions such as a typhoon. Failures can be avoided. Further, the motor includes switching means;
Since it can be realized by providing a resistor and a current detection device, it can be easily realized without the need to change the motor drive circuit itself, and moreover, it is possible to perform a highly reliable protective operation with an inexpensive configuration.

[Brief explanation of the drawing]

Figures 1 to 3 show one embodiment of the present invention, Figure 1 is a circuit diagram of a brushless DC motor using a brushless DC motor protection device, and Figure 2 shows the motor rotation speed, short circuit current and normal A characteristic diagram showing the relationship with the operating current, FIG. 3 is a flowchart of main parts of the motor drive control device in the same device, and FIG. 4 is a circuit diagram of a conventional brushless DC motor. 1... Armature winding, 8... Motor drive circuit, 11...
... Relay, 12... Resistor, 13... Motor drive control device, 14... Current detection device. Agent Yoshihiro Morimoto
Figure 2

Claims (1)

[Claims] 1. A switching means for switching and connecting an armature winding of a brushless DC motor to a motor drive circuit and a resistance circuit forming a closed circuit with the armature winding; A current detection device for detecting current, and an output of the current detection device are inputted, and when the detected output is below a certain value, the switching means is driven to connect the armature winding to the motor drive circuit side. Brushless DC motor protection device with motor drive control device.