JPS6311347Y2 - - Google Patents

Description

[Detailed explanation of the invention] This invention relates to a protection device for an electric compressor.
The purpose is to prevent the compressor from running out of gas.

In general, in so-called suction cool type electric compressors that are cooled by suction refrigerant gas, if refrigerant gas leaks and the motor runs out of gas, the temperature of the motor windings increases, resulting in burnout of the windings. The compressor will not be able to operate.

This proposal has been made in view of the above points, and the embodiment shown in the drawings will be described below.

1 is an operation switch, 2 is a stop switch, 3 is an electromagnetic switch for the compressor, and 4 is a switching circuit operated by an input signal from the temperature detection circuit 5. These are connected to form an operation control circuit for the electric compressor 6. At the same time, the first contact 3 of the compressor electromagnetic switch 3
A is connected in parallel to the operation switch 1, and a second contact 3b is connected in series to the timer 7.

The temperature detection circuit 5 has a negative characteristic thermistor 9 that senses the temperature of the discharge muffler 8 of the electric compressor 1 and a positive characteristic thermistor 11 that senses the temperature of the motor coil 10 connected in series. 9 is provided in parallel with a timer contact 7a which is a normally closed contact of the timer 7.

Next, the operation of the above configuration will be explained.

B. During normal operation First, when starting, the negative characteristic thermistor 9 that senses the temperature of the discharge muffler 8 is short-circuited in advance by the timer contact 7a of the timer 7, so the resistance value of the temperature detection circuit 5 is small, and the resistance value of the temperature detection circuit 5 is small. When closed, the switching circuit 4 is in the ON state, so the compressor electromagnetic switch 3 is excited, its first contact 3a and second contact 3b are both closed, and the electric compressor 6 starts operating. After a certain period of time has elapsed after the start, the timer contact 7a is opened by the timer 7, but at this point the temperature of the discharge muffler 8 has risen, so the resistance of the negative characteristic thermistor 9 decreases, and the temperature of the motor coil 10 is also low. The resistance value of the detection circuit 5 is small, and the switching circuit 4 is
The electric compressor 6 maintains the ON state and performs normal operation.

(b) During gas starvation operation When a gas starvation condition occurs due to a refrigerant gas leak, the temperature of the discharge muffler 8 decreases and the temperature of the motor coil 10 rises, causing both the thermistors 9,
All the resistances of 11 become high, and the temperature detection circuit 5
The resistance value becomes large, and as a result, the switching circuit 4 is turned off and the operation of the electric compressor 6 is stopped. This prevents the motor coil 10 from burning out and protects the electric compressor 6. The electric compressor 6 may be associated with the switching circuit 4 or may be provided in parallel with the timer 7.

As described above, the present invention is an electric compressor that includes a compressor having a discharge muffler and an electric motor that drives this compressor, and controls this electric motor by a signal from a temperature detection circuit. A negative characteristic thermistor that senses the temperature and a positive characteristic thermistor that senses the temperature of the motor coil are provided in series, and a timer contact that closes at startup is provided in parallel with the negative characteristic thermistor, so that there is no risk of gas starvation due to operation. Burnout of the electric motor is prevented and the electric compressor is safely protected.

[Brief explanation of the drawing]

FIG. 1 is an electric circuit diagram showing one embodiment of the present protection device, FIG. 2 is a cutaway front view of the main parts of an electric compressor, and FIG. 3 is a characteristic diagram of a thermistor. 4...Switching circuit, 5...Temperature detection circuit, 9...Negative characteristic thermistor, 11...Positive characteristic thermistor, 7a...Timer contact, 8...Discharge muffler, 10...Motor coil.

Claims (1)

[Scope of utility model registration request] An electric compressor that includes a compressor having a discharge muffler and an electric motor that drives the compressor, guides suction refrigerant gas to the compressor via the electric motor, and controls the electric motor with a signal from a temperature detection circuit, The temperature detection circuit includes a negative characteristic thermistor that senses the temperature of the discharge muffler and a positive characteristic thermistor that senses the temperature of the motor coil, which are connected in series, and a timer contact that closes at the time of starting is connected to the negative characteristic thermistor in parallel. A protection device for electric compressors featuring: