JPS63206187A - Protective device of brushless motor - Google Patents

Abstract

PURPOSE:To prevent a brushless motor against destruction by excessive current, by starting the operation of the motor only when the line voltage value is under a definite one, and by turning off a switching means for a limited time when the DC current value exceeds 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 and a driving means 6 of the switch group 2 are provided. Furthermore, a line voltage detective means 7 to detect the voltage across motor windings and its line voltage judging means 8, a DC current detective means 9 of the switch group 2 and its DC current judging means 10, a timer means 11 and a switching means 12 are provided to constitute a protective device. Thus, the strength of external wind force is detected with line voltage and when the voltage is over the definite value, the switching means 12 is turned off. The load condition is detected by the detective means 9 and when the DC current value is over the definite value, the switching means 12 is turned off for a limited time.

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 induction 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 forced to drive externally due to abnormally strong winds caused by a typhoon, excessive induced voltage is generated inside the brushless motor, a short-circuit current flows within the motor windings, and the semiconductors are destroyed. It had some problems.

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 line voltage detection means for detecting the line voltage of the motor, and an output of the line voltage detection means. A line voltage disconnection means for determining whether the line voltage exceeds a certain value, an opening/closing means inserted between the motor winding and the semiconductor switch group, and a DC current detection means for detecting the DC current flowing through the semiconductor switch group. and a DC current determining means for determining whether the output of the DC current detecting means exceeds a certain value, and a timer means for holding the output of the DC current determining means for a certain period of time, so that the line voltage value is a constant value. In the above case, the switching means is not turned on, and when the direct current value exceeds a certain value while the line voltage value is below a certain value during operation, the switching means is turned off for a certain period of time.

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 the output signal of the phase detection means 5; 7 is a line voltage detecting means for detecting the voltage between the motor windings; 8 is a line voltage detecting means for determining whether the line voltage value detected by the line voltage detecting means 7 exceeds a certain value. A line voltage determining means, 9 a direct current detecting means for detecting the value of the direct current flowing through the semiconductor switch group 2, and 10 a direct current detecting means for determining whether the direct current electronic value detected by the direct current detecting means 9 exceeds a certain value. 11 is a timer means for holding the output of the DC current determining means 10 for a certain period of time; and 12 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, 15 is a propeller fan, 16 is a brushless motor, and 17 is a heat exchanger.

Now, in order to cool the heat exchanger 17, the brushless motor 1
The ON 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 16 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 in which the brushless motor 16 is rotated in the opposite direction by external wind power. In this state, a short circuit current (solid line and dotted arrow) flows. This current naturally increases as the number of rotations of the brushless motor 16 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 16 exceeds a certain level, all the 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 16 and the line voltage with respect to the wind speed when the brushless motor 16 is rotated by external wind power when all the elements of the semiconductor switch group 2 are in the OFF state. In the present invention,
The strength of the external wind force is detected by the line voltage, and when the line voltage exceeds a certain value, the opening/closing means 12 is turned off, and the external wind force increases while the brushless motor 16 is being operated with the line voltage below a certain value. When the load on the brushless motor 16 increases, the load condition is detected by the DC current detection means 9, and when the DC current value exceeds a certain value, the opening/closing means 12 is turned off for a certain period of time.
By FF, the winding 3 of the brushless motor 16
This prevents excessive current flowing through the semiconductor switch group 2, and also prevents joint hunting.

FIG. 6 shows a flow chart of the present invention.

FIG. 7 shows a specific embodiment of the photocoupler 218'!
: Detect the line voltage VAC of the υ motor and set the reference voltage 26
and is compared by the comparator 23. Here, when the outdoor fan operation command is not issued (when the outdoor fan is stopped), the reference voltage 26 is set to zero, the transistor 24 is turned off, and the relay 25 is always kept in the OFF state. When an outdoor fan operation command is issued, the reference voltage 26 is set to a certain appropriate value and compared with the line voltage detection value detected by the photocoupler 21. When the line voltage value is above a certain value, the DC current is detected by the resistors 2B and 29.30, and compared with the reference voltage 27 by the comparator 31, and when the DC current value is above the certain value, The relay 25 is turned off by holding the output signal of the comparator 31 for a certain period of time using the monostable multi-by-break 32.

Note that 22 is a flywheel diode.

Effects of the Invention As described above, the present invention provides a system for driving an outdoor fan of a brushless smoker air conditioner, including a line voltage detection means for detecting voltage between motor windings, and a line voltage detection means for detecting voltage between motor windings, and a line voltage detection means for detecting voltage between motor windings. line voltage determining means for determining whether the voltage has exceeded the line voltage, opening/closing means inserted between the semiconductor switch group and the motor winding, direct current detection means for detecting the direct current flowing through the semiconductor switch group, and direct current detection means for detecting the direct current flowing through the semiconductor switch group; DC current determination means for determining whether or not the DC current exceeds a certain value;
A timer means is provided to hold the output of the disconnection means for a certain period of time,
When the line voltage value is above a certain value, the switching means is turned off.
In other words, only when the line voltage value is below a certain value is the condition for starting brushless motor operation.Furthermore, if the load increases during operation, the load state is detected by DC current, and the DC current value is kept at a constant value. If the voltage exceeds the limit, the opening/closing means is turned off for a certain period of time.With a simple configuration, even if the brushless motor is forcibly rotated forward due to abnormal external wind force such as a typhoon, excessive current will flow through the windings of the brushless motor. First, it is possible to prevent 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 element 1 is OFF, Figure 4 is a circuit diagram showing the operating state of the protection device of the same brushless motor during forward rotation, and Figure 5 is the same brushless motor. FIG. 6 is a circuit diagram showing the operating state of the motor protection device during reverse rotation, FIG. 6 is a flow chart of the brushless motor protection device, and 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... ...Line voltage judgment means, 9
・River: DC current detection means, 10: DC current or disconnection means, 11. River: Timer means, 12...
・Opening/closing means. Name of agent: Patent attorney Toshio Nakao and one other person? −
Manual lesson 1. +Group a-Ming Figure 2 Figure 3 A Speed Figure 4 Figure 6

Claims (1)

[Claims] A group of semiconductor switches constituting 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 a means for rotating the rotor in a fixed direction based on an 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. line voltage detection means; line voltage determination means for determining whether the line voltage value detected by the line voltage detection means exceeds a certain value; and a direct current for detecting a direct current flowing through the semiconductor switch group. It is comprised of a current detection means, a DC current determination means for determining whether the DC current value exceeds a certain value, and a timer means for holding the output signal of the DC current determination means for a certain period of time, and the line voltage value is If the voltage is above a certain value, the opening/closing means is not turned on and no short-circuit current is allowed to flow through the motor windings, and the direct current value exceeds a certain value while the line voltage value is below a certain value. A brushless motor protection device configured to turn off the opening/closing means for a certain period of time.