JPS63206189A - Brushless motor protection device - Google Patents

Abstract

PURPOSE:To prevent a semiconductor switch group against destruction by excessive current, by starting the operation of a brushless motor only when the line voltage value is under a definite one. CONSTITUTION:From a DC power source 1 a semiconductor switch group 2 to control the current of a winding 3 of a brushless motor, a phase detective means 5 of a rotor 4, and a driving means 6 of the switch group 2 are provided. Furthermore, a voltage detective means 7 across the motor winding, a voltage judging means 8 and a switching means 9 are provided to constitute a protective device. The strength of external wind force is thus detected with the line voltage and when it is over a definite value, the excessive current flowing through the winding 3 of the brushless motor and the switch group 2 can be prevented by turning off the switching means 9.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a protection device for a brushless motor when the brushless motor is applied to drive an outdoor fan of an air conditioner.

BACKGROUND OF THE INVENTION In recent years, efforts have been made to improve the operating efficiency of fan drive motors for the purpose of highly efficient operation of air conditioners. Therefore, the conventionally used injection motors are being replaced with brushless motors, which have higher operating efficiency. Particularly in separate air conditioners, many of the indoor fan motors are brushless motors, and the use of outdoor brushless motors is being considered in the future.

Problems to be Solved by the Invention However, when a brushless motor is applied as a motor for driving an outdoor fan of a separate air conditioner,
When the fan is forcibly driven from the outside due to abnormally strong winds caused by a typhoon, excessive induced voltage is generated inside the brushless motor, short-circuit current flows through the motor windings, and semiconductors are destroyed. It had a point.

In view of the above problems, the present invention provides a brushless motor protection device that prevents semiconductors from being destroyed by short-circuit current even if the fan is forcibly driven from the outside.

Means for Solving the Problems In order to solve the above problems, the brushless motor protection device of the present invention includes a line voltage detection means for detecting the line voltage of the motor, and an output of the line voltage detection means. It consists of a judgment means for determining whether or not a certain value has been exceeded, and an opening/closing means inserted between the motor windings and a group of semiconductor switches. OF the means
The configuration is such that F.

According to the brushless motor protection device of the present invention, even if the fan is forcibly driven from the outside due to abnormally strong winds caused by a typhoon, short-circuit current will not flow through the motor windings, and semiconductors will be protected from excessive current. can be prevented from being destroyed.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a basic configuration diagram of the present invention. In the same figure, 1
2 is a DC power supply, and 2 is a group of semiconductor switches that control the current flowing through the winding 3 of the brushless motor. 4 is a rotor of a brushless motor, which is composed of a permanent magnet. 5 is a phase detection means for detecting the magnetic pole position of the rotor 4; 6 is a phase detection means for generating a signal necessary for rotating the rotor 4 in a certain direction based on a high-force signal from the phase detection means 5; A driving means for driving 2, a line voltage detecting means 7 for detecting the voltage between the motor windings, and a line voltage detecting means 8 for determining whether the line voltage level detected by the line voltage detecting means 7 exceeds a certain value. 9 is an opening/closing means inserted between the semiconductor switch group 2 and the motor winding 3.

FIG. 2 is a configuration diagram of an outdoor unit of an air conditioner.

In the figure, 11 is a propeller fan, 12 is a brushless motor, and 13 is a heat exchanger.

Now, in order to cool the heat exchanger 13, the brushless motor 1
The ○N and OFF states of the semiconductor switch group 2 when the semiconductor switch group 2 is rotated in a fixed direction will be explained with reference to FIGS. 4 and 5.

FIG. 4 shows the state when the brushless motor 12 is rotated in the forward direction by external wind power. In this state, no current flows through the motor winding 3, and only between the upper and lower arms of the semiconductor switch group 2. Only the DC voltage vDc increases.

On the other hand, FIG. 5 shows a state when the brushless motor 12 is rotated in the opposite direction by external wind power. In this state, a short-circuit current (solid line and dotted arrows) flow. This current naturally increases as the number of rotations of the brushless motor 12 increases, and eventually destroys the elements of the semiconductor switch group 2.

Therefore, when the number of rotations in the reverse direction of the brushless motor 12 exceeds a certain level, all elements of the semiconductor switch group 2 are turned off.
Must be kept in FF state.

FIG. 3 shows the relationship between the rotational speed of the brushless motor 12 and the line voltage with respect to the wind speed when the brushless motor 12 is rotated by external wind power when all the elements of the semiconductor switch group 2 are in the FF state. . In the present invention, the strength of the external wind is detected by the line voltage, and when the line voltage exceeds a certain level, the opening/closing means 9 is turned OFF, thereby reducing the excessive current flowing through the winding 3 of the brushless motor 12 and the semiconductor switch group 2. It prevents electric current.

FIG. 6 shows a flowchart representing the above operation.

FIG. 7 shows a specific example in which the line voltage VAC of the winding 3 of the brushless motor is detected by resistors 21 and 22,
The output is rectified by a diode bridge 23 and a smoothing capacitor 24, and a detection voltage 25 proportional to the line voltage VAC is applied.
get. By comparing the detected voltage 25 and the reference voltage 29 with the comparator 26, when the line voltage VAC becomes a certain level or more (when the detected voltage 25 becomes more than the reference voltage 29), the transistor 27 Leh 28
This is to cut off the power supply and turn off the relay 28.

Here, when the outdoor fan operation command is not issued (when the outdoor fan is stopped), the reference voltage 29 is set to zero, and the relay 2
Keep B always OFF. When an outdoor fan operation command is issued, the reference voltage 29 is set to a certain appropriate value and compared with the line voltage detection voltage 25 by a comparator 26.

Note that 30 is a flywheel diode.

Effects of the Invention As described above, the present invention provides a system in which a brushless motor is applied to drive an outdoor fan of an air conditioner. A means for determining whether the line voltage exceeds #4J and a switching means inserted between the semiconductor switch group and the motor winding are provided, and when the direct line voltage exceeds a certain level, the switching means is turned OFF. The brushless motor starts operating only when the inter-voltage voltage is below a certain level.With a simple configuration, even if the brushless motor is forcibly rotated by abnormal external wind force caused by a typhoon, the winding of the brushless motor will not start. This prevents excessive current from flowing through the wires and prevents damage to the semiconductor switch group due to excessive current.

[Brief explanation of the drawing]

Fig. 1 is a basic configuration diagram of a protection device for a brushless motor showing an embodiment of the present invention, Fig. 2 is a configuration diagram of an outdoor unit of an air conditioner, and Fig. 3 is a basic configuration diagram of a protection device for a brushless motor showing an embodiment of the present invention. A characteristic diagram showing the relationship between wind speed, line voltage, and motor rotation speed when the element is turned off. Figure 4 is a circuit diagram showing the operating state of the protection device of the same brushless motor during forward rotation. Figure 5 is the same diagram. FIG. 6 is a flowchart of the brushless motor protection device; FIG. 7 is a circuit diagram showing an embodiment of the brushless motor protection device. . 2... Semiconductor switch group, 5... Phase detection means, 6... Drive means, 7... Line voltage detection means, 8... ...Judgment means, 9...
・Opening/closing means. Do - Tehakabuchi Minato≠ 3-! L & q - Opening/closing means Figure 1? Fig. 2 Fig. 3 Aki Sho Fig. 4 1°0,・ Fig. 6

Claims (1)

[Claims] A semiconductor switch group for controlling the winding current of the brushless motor, a phase detection means for detecting the magnetic pole position of the rotor composed of a permanent magnet, and for rotating the rotor in a fixed direction based on the output signal of the phase detection means. A driving means that generates a necessary signal and drives the semiconductor switch group using the signal, an opening/closing means inserted between the motor winding and the semiconductor switch group, and a voltage between the motor windings that is detected. It is comprised of a line voltage detection means and a judgment means for determining whether the line voltage value detected by the line voltage detection means exceeds a certain value, and when the line voltage value exceeds the certain value. A protection device for a brushless motor is configured to turn off the opening/closing means.