JPS60166773A - Method for stopping motor-driven compressor - Google Patents

Abstract

PURPOSE:To enable long life of a motor-driven compressor by realizing soft stop by once electrifying a motor through a voltage drop type transformer at the time of stop and interrupting electricity to the motor, in the motor-driven compressor provided with the voltage drop tupe transformer. CONSTITUTION:When stopping a motor-driven compressor during operation, a switch 31 is opened. Then a contact 32a1 is opened but a contact 33a1 is closed. But a contact 32a2 is opened and a contact 34a is also opened. At the same time a contact 32b1 is closed and contacts 35a1, 35a2 are closed. Then a motor 21 is connected to a single phase AC power supply through a voltage drop type transformer 38 and at the same tine contact 32b2 is closed and as a contact 33a3 is closed, a timer 36 is excited. And when set time elapsed, a limit time constant open contact 36a is closed, then a contact 37 is opened and the motor 21 is stopped. Therefore, shock at the time of stop of the motor 21 can be minimized.

Description

[Detailed description of the invention] The present invention relates to a method for stopping an electric compressor.

For example, in a conventional reciprocating electric refrigeration compressor, as shown in the vertical cross-sectional view of FIG. The internal mechanism is suspended from the housing 6 by a suspension mechanism (not shown), and compressed gas passes through a shock loop 7 and is discharged to the outside.

The induction motor used to drive such a compressor is a single-phase induction motor 21 as shown in the circuit diagram of FIG. 2, and is connected to the power supply by a switch 22 outside the compressor.
The switch 22 is closed to operate, and the switch 22 is opened to stop the operation. In the roof tile, 23 is a driving capacitor, 24 is an auxiliary coil, and 25 is a main coil.

However, such electric refrigeration compressors have the following problems when stopped.

In other words, when stopping the compressor, if the switch 22 is momentarily opened, approximately 360011111 (
An electric motor that generates torque while rotating with a 2-pole 6011z power supply will momentarily stop generating torque, whereas a rotating body has inertia and tries to continue rotating due to inertia, while the load There is gas inside the cylinder of the compression section.
Even if the power is cut off, the compressor function remains intact.

Therefore, as long as the rotational force due to inertia is greater than the force compressing the gas, even if the power is cut off, the rotation speed will gradually decrease because the gas will continue to rotate due to inertia while compressing the gas. Accordingly, the inertial force gradually decreases, and when the inertial force becomes less than the repulsive force of gas pressure, the compressor suddenly stops.

When this sudden stop occurs, a force in the opposite direction to the rotational direction acts on the internal mechanisms 1 to 4, and this force is absorbed by the suspension mechanism and shock loop 7, but if it is too large to be absorbed, the force is ...It is transmitted to Uzing 6, causing large vibrations throughout the compressor.

As a result, a large force is applied when the compressor stops, which shortens the life of the shock loop 7 and suspension mechanism, and the life of the entire compressor and its external piping is also shortened due to the amount of vibration and the number of times the compressor stops. Put it away.

The present invention has been proposed in view of the above circumstances, and an object of the present invention is to provide a method of stopping an electric compressor that can be stopped quietly and prolonging the life of an electric compressor.

To this end, the present invention provides an electric compressor equipped with a step-down transformer, in which when the compressor is stopped, power is first supplied to the motor via the step-down transformer, and then power to the motor is cut off.

An embodiment of the present invention will be described with reference to the drawings. FIG. 3 is a circuit diagram thereof.

In the above figure, the same symbols as in Fig. 2 indicate the same members as in the same figure, 31 is a start/stop switch, 32 is an auxiliary relay, 32al132a is its normally open contact, 32b
,,32b.

is its normally closed contact.

33 is a relay, 33a+ 133a+.

33a is the normally open contact, 34 is the relay, 34a is the normally open contact, 35 is the relay, 35a+, 35a+ is the normally open contact, 36 is the timer, 36a is the normally open time contact, 37 is the auxiliary relay, 37b is its normally closed contact, and 38 is a step-down transformer.

Such a circuit operates as follows.

(1) Starting and operation: By closing switch 31 during starting, relay X+ 32 is energized, so contact 32a
1 is closed, relay 52.33 is energized, and contact 33a is closed.

At the same time, contact 32a2 is closed and relays X and 34 are excited, so contact 34a is closed and single-phase AC power is supplied to motor 21.

At this time, contact 33a2 is closed. Then, relays 52 and 33 are self-held.

Further, since contacts 32b, 32b are open, relays X and 35 and timer 36 are not energized, and therefore relays X and 37 are also not energized.

This condition continues while driving.

(2) When stopped: To stop the compressor during operation, use the switch. switch 31 is opened.

Then, relays X and 32 are de-energized and the contact point 32a1 is opened, but since the relays 52 and 33 are self-held by the contact point 33a2, they remain energized, and therefore the contact point 33a is also closed. ing.

However, since contact 3 "2a" is open, relay X23
4 becomes non-energized, the contact 34a becomes open.

At the same time, contact 321) is closed, so relay
5 is excited, and contacts 35a and +35at are closed.

In this way, the electric motor 21 is connected to the single-phase AC power supply via the step-down transformer 38, and at the same time, the contact 3
Since the contact 2b2 is closed and the contact 33a is closed, the timer ~36 is excited and starts timing.

After the set time of timer 36 has elapsed. Then, the time-limited normally open contact 36a is closed.

') Ray-X, 37 is excited, so the contact 37b is opened, the power supply to the motor is cut off, and the motor 21
stops.

According to such a circuit, the lower the voltage applied to the electric motor, the smaller the torque generated by the electric motor becomes. , the motor generates less torque and continues operating.

Eventually, the torque generated by the motor becomes smaller compared to the load such as gas pressure, and the motor gradually stalls and eventually stops, but in addition to the rotational inertia force, a torque in the rotational direction is generated, albeit a low torque. As a result, the torsional force at the time of stopping due to the repulsive force of the gas pressure in the cylinder cancels each other out and weakens, so the shock at the time of stopping becomes smaller.

Although the above embodiment has been described with reference to a single-phase motor, it can also be easily implemented with a three-phase motor.

In short, according to the present invention, in an electric compressor equipped with a step-down transformer, when the electric compressor is stopped, power is first supplied to the motor through the step-down transformer, and then the power to the motor is cut off, thereby extending the life of the electric compressor. The present invention is industrially extremely useful because it provides a stopping method that can be used in a variety of situations.

[Brief explanation of the drawing]

FIG. 1 is a vertical sectional view showing a known reciprocating electric refrigeration compressor, FIG. 2 is a circuit diagram of FIG. 1, and FIG. 3 is a circuit diagram showing an embodiment of the present invention. 23... Operating capacitor, 24... Auxiliary coil, 25
...Main coil, 31...Start/stop switch, 32
... Auxiliary relay, 32a, 32at +++ Normally open contact, 32b, 32
b,...Normally closed contact, 33...Relay, 33a+H
33at 133a+... Normally open contact, 34... Relay, 34a... Normally open contact, 35... Relay, 35a
1135a2... Normally open contact, 36... Timer, 3
6a... Normally open time contact, 37... Auxiliary relay, 37
b... Normally closed contact, 38... Step-down transformer. Sub-Agent Patent Attorney Masafumi Tsukamoto

Claims (1)

[Claims] In an electric compressor equipped with a step-down transformer, when the motor is stopped, electricity is first supplied to the motor via the step-down transformer, and then
A method for stopping an electric compressor, comprising cutting off power to the electric motor.