JPS63268492A - Driving device of brushless motor - Google Patents

Abstract

PURPOSE:To control the pulsation of motor winding current and to minimize the current capacity of a switching element, by providing a motor winding current limiting circuit which actuates when the motor winding current exceeds the preset limit value. CONSTITUTION:A measurement, operation and control circuit 7 of rotating speed gives control signals to a semiconductor commutator circuit 9 through a drive circuit 8 in accordance with the outputs of a rotor position detection circuit 6, a rotating speed command value generation circuit 10 and an average current detection circuit 11. On the other hand, a current limiting circuit 12 interrupts the signal of a drive circuit 8 to limit the winding current when the winding current exceeds the preset limit value. In this way, the current capacity of a switching element can be minimized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a brushless motor drive device, and particularly to a brushless motor drive device that limits motor winding current and controls one of the switching elements of an inverter.
The present invention relates to a drive device for a plastic/less motor suitable for reducing 1L flow capacity.

[Conventional technology]

A conventional device has the following configuration, as described in, for example, Japanese Patent Application Laid-Open No. 149782/1982. That is,
To control the rotational speed of a brushless motor in a brushless motor drive device for an air conditioner that has a refrigeration cycle configured with a refrigerant compressor etc. driven by a brushless motor that can rotate at rotational speed II (@l). The voltage applied to the brushless motor is controlled.

[Problem that the invention seeks to solve]

The above-mentioned conventional technology does not take into consideration ripples in the DC voltage applied to the brushless motor and pulsations in the motor winding current caused by pulsating torque due to refrigerant gas compression, and as shown in FIGS. 3 and 4, Flow through the motor windings in detail.
was pulsating. Figure 3 shows the applied voltage ■ and the winding current ■
This is a diagram showing the relationship between the vertical axis and the applied voltage.
The magnitude of L flow l is shown, and the horizontal axis shows time t. FIG. 4 is a diagram showing the relationship between the torque 'r and the winding current l, where the vertical axis shows the magnitude of the torque T and the winding current, and the horizontal axis shows the time t. Therefore, it is necessary to use a switching element that can withstand the peak value of the motor winding current, resulting in the problem of an increase in the current capacity of the switching element.

An object of the present invention is to suppress pulsation of motor winding current and reduce the current capacity of a switching element.

[Means for solving problem 1] The above object is to provide a detection circuit for the motor winding + tts'tpta flowing through the switching element in a brushless motor drive device, and to detect the motor winding current exceeding a preset limit value. This is achieved by providing a motor winding IWt flow limiting circuit which is activated when

[Effect]

The rotational speed e of the brushless motor changes in proportion to the magnitude of the applied pressure, and the magnitude of the winding current is proportional to the motor shaft output torque. Therefore, when the applied voltage fluctuates due to ripples, or when the motor load torque fluctuates due to gas compression, pulsations occur in the motor winding current, that is, the current flowing through the switching element of the planless motor drive device, and the switching element A current capacity that can withstand the peak value of pulsating current is required.

The present invention uses a current i15+1 limiting circuit to control the motor winding current so that it does not flow beyond a preset limit value, and when pulsation occurs in the current, the peak value above This is to keep the value within the limit value.

Assuming that the moment of inertia of the rotating system of the flangeless motor and compressor is J1, the angular velocity is ω, the gas compression torque of the compressor is TG, and the motor shaft output torque is TM, the moment of force of this rotating system satisfies the following equation.

J-Mill-1-TG-’IL”M-Q t In this system, if the motor winding current is limited.

During the period when the current is restricted, the shaft torque 'vM is insufficient, but the moment of inertia Jdw releases energy to make up for this deficiency. As a result, although the rotational speed t of the motor decreases, the brushless motor can maintain full rotation.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail. FIG. 1 is an overall configuration diagram of an air conditioner equipped with a brushless motor drive device i1 showing an embodiment of the present invention. lri refrigerant refrigerant compression compressor, 2 and 2' are heat exchangers, 3 and 3' are blowers, and 4 is a pressure reducer. ′＠It constitutes a freezing cycle. 5t/i compressor drive brushless motor, 6 is a rotor position detection circuit, 7 is a rotational speed measurement/calculation/control circuit, 8 is a drive circuit, 9 is a semiconductor commutator circuit, 10 is a rotational speed command generation circuit , 11 is the average I
A La detection circuit, 12 a t-current limiting circuit, and 13 a motor winding current detection circuit, these constitute a brushless motor drive device.

In this embodiment, a winding current detection circuit 13 is provided in the brushless motor drive device, and when the winding tlL flow exceeds a preset limit value, the '#lt flow limiting circuit is activated and the drive circuit 8 is The signal is cut off and the winding current is limited as shown in FIG. During the period when the current is limited, the energy generated by the motor decreases and the rotational speed decreases, but as shown in Figure 2, the lack of energy is compensated for during the period when the pulsating current is low, and the average rotational speed increases. Rotation speed command generation circuit lO
The rotational speed is controlled to be equal to the rotational speed rudder command sent from the controller.

Also, the load on the motor increases and i! If the winding current always reaches the limit value rC due to the rigidity of the current limiting circuit 12, it will be impossible to continue operating the motor if the load increases further. Therefore, an average current detection circuit 11 is provided, and when the average current exceeds the limit value, the motor rotation speed is reduced regardless of the rotation speed, reducing the operating load and preventing motor operation in the event of an overload. Make it last.

As described above, according to this embodiment, it is possible to drive a brushless motor while suppressing the peak value of the current flowing through the switching of the flangeless motor drive device.

〔Effect of the invention〕

According to the present invention, since the peak value of the motor winding i'a current flowing through the switching element of the brushless motor drive device can be suppressed, the current capacity of the switching element can be reduced.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of an air conditioner equipped with a bra/less motor drive device showing an embodiment of the present invention, and FIG.
FIGS. 3 and 4 are diagrams showing the winding 111, a controlled by the illustrated drive device, and FIGS. 3 and 4 are diagrams showing the relationship between the applied voltage and load torque applied to the winding and the winding current. 1...Compressor, 2...Heat exchanger, 3...Blower,
4... Pressure reducer, 5... Brushless motor, 6...
Rotor position detection circuit, 7...Rotational speed measurement/calculation/
Control circuit, 8... Drive circuit, 9... Semiconductor commutator circuit, 10... Rotation speed command generation circuit, 11
... Average current detection circuit, 12 ... Current limit circuit, 1
3... Current detection circuit. Representative Patent Attorney Katsuo Ogawa] I No. 1 Figure 1--71 Silkwood' 5--τ Lasires 7-ta t+---LIII Burning) 1 Projection circuit + 2- @:, circle! #jF1 times 16 B--@shiL detection circuit

Claims (1)

[Claims] 1. In a brushless motor drive device that drives a brushless motor using an inverter, a means for detecting a motor winding current flowing through a switching element of the inverter, and a motor winding that is activated when the motor winding current exceeds a preset limit value. A brushless motor drive device comprising current limiting means.