JPH0736670B2 - Electric compressor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to an electric circuit of an electric compressor applied to an air conditioner or the like.

(Problems to be Solved by Prior Art and Invention) As one conventional example of this type, there is a circuit configuration shown in FIG.

1 is a main winding of an electric motor, 2 is an auxiliary winding that generates 90 ° phase-advancing magnetic flux with it, 3 is an overload relay that shuts off the circuit when an overcurrent flows through the load, and 6 is an operating (phase shifting) capacitor ,
7 is a so-called positive characteristic thermistor starter (hereinafter referred to as "PTC starter") in which the electric resistance of the semiconductor increases as the temperature rises.
, 8 is a commercial AC power supply.

In the conventional example shown in FIG. 5, since a relatively large current flows through the auxiliary winding 2 through the PTC starter 7 having a low resistance value at the time of starting, starting is performed with a large torque. Since the resistance value of the PTC starter 7 increases during normal operation, only a predetermined current flows through the auxiliary winding 2 through the capacitor 6. In this case, only the current of the main winding 1 flows through the overload relay 3 and the trip does not occur in a normal operating state. On the other hand, when restrained, the currents flowing through the main winding 1 and the auxiliary winding 2 both increase, but the overload relay 3 trips in accordance with the increase in the current flowing through the main winding 1.

Further, FIG. 6 is a circuit diagram showing the configuration of another conventional example.

This places the overload relay 3 in the main circuit of the electric compressor,
The PTC starter 7 was connected in parallel with the operating capacitor without the overload relay 3.

However, in the conventional example (Fig. 5), the PTC
When the starter 7 suffers a short circuit failure, an excessive current continues to flow in the auxiliary winding 2 and the auxiliary winding 2 is burned out.

Also in the other conventional example (FIG. 6), similarly, the PTC starter 7 fails and the winding burnout cannot be protected at the time of short circuit.

For this reason, a method of inserting and connecting an overcurrent relay or a fuse in the circuit of the PTC starter 7 or the circuit of the auxiliary winding 2 is conceivable, but there is a problem in that the cost increases because extra parts are required.

Further, in the case of FIG. 5, when the operating current of the electric compressor is large, it is difficult to adjust the current operating point with the overload relay 3, that is, the temperature is high during operation, and thus tripping is easy,
On the other hand, if it is set so that it will not trip during operation, it will not trip even when the electric compressor is locked at low temperatures, making it difficult to protect the electric compressor.

Therefore, assuming that the auxiliary winding 2 is prevented from being burnt in the case of a short circuit failure of the PTC starter 7 of the above-mentioned conventional example,
There is a circuit configuration shown in FIG. In the figure,
The overload relay 3 comprises a bimetal contact 4 and a heater 5 as a breaking unit, and an operating capacitor 6 and a PTC starter 7 are connected in parallel via the heater 5.

Therefore, with such a configuration, when restrained or when the PTC starter 7 has a short-circuit failure, current flows through the heater 5 to generate heat and the operating time of the bimetal contact 4 is shortened, thereby improving the protective characteristics of the electric compressor. You can

However, the one shown in FIG. 4 has a configuration in which the operating capacitor 6 is connected to the power source 8 via the overload relay 3, and not only the main winding 1 but also the auxiliary winding 2 during normal operation. Since the flowing current flows to the overload relay 3,
There is a risk of malfunction of the overload relay 3.

Here, the present invention overcomes the disadvantages of the conventional example, and provides an electric compressor that prevents burnout of the auxiliary winding when the PTC starter has a short-circuit fault, without malfunction of the overload relay during operation. To aim.

[Structure of Invention]

(Means for Solving Problems) A main winding connected to a power supply via an overload relay, and an auxiliary winding connected to a power supply via an overload relay and via a positive temperature coefficient thermistor starter, One end is connected between the power supply and the overload relay, and the other end is provided with an operating capacitor connected between the positive temperature coefficient thermistor starter and the auxiliary winding.

(Operation) From the circuit configuration according to the present invention, the resistance value of the PTC starter increases under normal conditions, almost no current flows there, and the overload relay does not malfunction during operation.

Further, even when the PTC starter has a short circuit failure, the overload relay is inserted and connected to the auxiliary winding circuit, so that the auxiliary winding is not burned.

(Embodiment) An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

FIG. 1 is a circuit diagram showing the configuration of an embodiment of the present invention.

The main winding 1 is connected to the power supply 8 via the overload relay 3,
In the circuit of the auxiliary winding 2, the PTC starter 7 is connected to the power supply 8 via the overload relay 3, and the operating capacitor 6 is a means directly connected to the power supply 8 without passing through the overload relay 3.

With such a connection configuration, an excessive current several times as large as the current that normally flows in the auxiliary winding 2 flows when the PTC starter 7 has a short circuit failure. This excessive current flows through the overload relay 3 together with the current of the main winding 1, whereby the overload relay 3 operates and burnout of the auxiliary winding 2 is prevented.

On the other hand, when the PTC starter 7 is operating normally, the resistance value increases during operation after the compressor is started, and only a current of several mA to several tens mA flows. Therefore, the current flowing through the overload relay 3 is hardly changed by the PTC starter 7, and the malfunction of the overload relay 3 does not occur.

Circuit configurations of other embodiments of the present invention are shown in FIGS. 2 and 3, respectively.
Shown in the figure.

These are the PTC starter 7 and the heater 5 of the overload relay 3.
The circuit is connected to the circuit.

In this way, the PTC starter 7 is connected to the heater 5 of the overload relay 3.
If the circuit is connected to the above circuit, the overload relay 3 operates more quickly and surely due to the heat generation of the heater 5 due to the current when the PTC starter 7 short-circuits, and the protection characteristic is improved.

In addition, in FIG. 2 and FIG. 3, the PTC starter 7
If a short circuit occurs in the heater 5, the heater 5 may be blown by an excessive current.

〔The invention's effect〕

Thus, according to the present invention, among the auxiliary winding circuits, only the PTC starter is connected to the power source via the overload relay, so that the following remarkable effects can be obtained.

It is possible to prevent the auxiliary winding from being burnt out when the PTC starter is short-circuited, without the overload relay malfunctioning due to an increase in the operating current flowing through the overload relay.

It is cheaper than the method of inserting and connecting an overcurrent relay or a fuse in the auxiliary winding circuit.

It is easy to adjust the operating point of the overload relay even if the operating current is relatively large.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing the structure of an embodiment of the present invention, FIGS. 2 and 3 are circuit diagrams showing the structure of another embodiment of the present invention, and FIGS. 2 is a circuit diagram showing the configuration of the electric compressor of FIG. DESCRIPTION OF SYMBOLS 1 ... Main winding of motor, 2 ... Auxiliary winding of motor, 3 ... Overload relay, 4 is a breaking part, 5 is a heater, 6 ... Operating capacitor, 7
… Positive temperature coefficient thermistor starter (PTC starter), 8… Power supply.

Claims (3)

[Claims] 1. A main winding connected to a power supply via an overload relay, an auxiliary winding connected to the power supply via the overload relay and via a positive temperature coefficient thermistor starter, and one end of the power supply. An electric compressor comprising: an operating capacitor connected between the overload relay and the other end connected between the positive temperature coefficient thermistor starter and the auxiliary winding. 2. A thermal dynamic overload relay comprising a bimetal and a heater, wherein the PTC thermistor starter is connected to a heater circuit of the overload relay.
The electric compressor according to the item. 3. The electric compressor according to claim 2, further comprising a heater which is blown by an overcurrent when the short circuit failure of the positive temperature coefficient thermistor starter occurs.