JPH028539Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a start-up protection device for an induction motor, which houses a positive temperature coefficient thermistor element and an overload relay in one exterior case and is attached to the motor.

Conventionally, in a protection device for an induction motor, in which a starting current is passed through a motor (single-phase induction motor) using a positive characteristic thermistor element to start the motor, and an overload relay is used to cut off the overcurrent flowing through the motor, for example, As shown in FIG. 1, the overload relay 11 and the PTC thermistor element 12 are attached separately to the induction motor 13, or as shown in FIG. was thermally coupled and attached to the electric motor 13.

By the way, if the overload relay 11 and the positive temperature coefficient thermistor element 12 are separately attached to the induction motor 13 as shown in FIG. Although it sensitively reacts to the heat of the electric motor 13 and has excellent protection performance for the electric motor 13, it has disadvantages in that it requires a large installation space and the electrical connections for installation are complicated. Furthermore, since the recovery time after activation of the overload relay 11 is usually shorter than the recovery time of the positive temperature coefficient thermistor element 12, the above-mentioned separate installation has the disadvantage that the motor 13 cannot be restarted. . In order to eliminate this drawback, it is necessary to use an overload relay 11 with small variations in operating temperature and return temperature, which increases the cost of the motor start-up protection device.

On the other hand, when the overload relay 11 is configured as shown in FIG.
Since the recovery time of the overload relay 11 can be matched with the recovery time of the positive temperature coefficient thermistor 12 after receiving the residual heat of the motor 13, restarting the electric motor 13 becomes easy. However, in this case, the overload relay 11 is not easily exposed to the heat of the electric motor 13, and the protection performance when the electric motor 13 generates abnormal heat is not sufficient.

The present invention was devised in view of the above-mentioned circumstances regarding conventional motor start-up protection devices, and its purpose is to arrange the overload relay so that it efficiently receives heat from both the motor and the positive temperature coefficient thermistor element. The purpose is to reliably protect the electric motor in the event of an abnormality and to facilitate restarting the electric motor.

For this reason, the present invention accommodates a positive temperature coefficient thermistor element and an overload relay in one exterior case so that the overload relay is disposed between the induction motor and the positive temperature coefficient thermistor element. In the attached induction motor starting protection device, the above-mentioned exterior case is provided with a support member that separates the overload relay accommodating portion and the positive temperature coefficient thermistor element accommodating portion, and this support member is provided with the above two accommodations. A communication hole is provided to communicate the sections with each other, and an opening is provided on the mounting surface to the induction motor that faces the housing section of the overload relay.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 3 shows a starting protection device for an induction motor according to the present invention.

In Fig. 3, 21 is an overload relay;
22 is a positive temperature coefficient thermistor element, 23 is an exterior case that houses the overload relay 21 and the positive temperature coefficient thermistor element 22, 24 is a support member that supports the overload relay 21, and 25 is an outer casing for the motor, compressor, etc. be.

The overload relay 21 includes a bimetal 28 having contacts 26 and 27 at both ends, a temperature adjustment screw 29 that supports the bimetal 28 at its center, and a heater 30 that heats the bimetal 28.
and fixed contacts 31, 32, etc., with which the contacts 26, 27 contact, respectively.

The bimetal 28 is fitted between the head 29a of the temperature adjustment screw 29 and a washer 29b non-removably attached to the lower part of the head 29a so that the temperature adjustment screw 29 can rotate. ,
The threaded portion of the temperature adjustment screw 29 is screwed into a threaded hole 24b located approximately at the center of the support portion 24a of the support member 24.

On the other hand, the fixed contacts 31 and 32 are formed by insert molding or the like into the support portion 24a of the support member 24.
One end of the fixed contact 31 is bent at a right angle so that it can come into contact with the contact 26 of the bimetal 28, and the other end of the fixed contact 31 is similarly bent at a right angle to connect the glass of the motor 25. The tip of the conductive plate 36 connected to the socket 35 of the pin terminal 34 of the terminal 33 is welded.

The heater 30 has one end connected to one end of the fixed contact 32 and the other end connected to the support portion 24 of the support member 24.
They are respectively welded to support metal fittings 37 fixed to a, and the support metal fittings 37 are drawn out of the exterior case 23 by a conductive plate 38.

The support member 24 is housed in a housing part 39 of the overload relay 21 in the outer case 23, and a housing part 40 of the PTC thermistor element 22 between the housing part 39 and the bottom part 23a of the outer case 23 includes:
The positive temperature coefficient thermistor element 22 is sandwiched between the terminal plate 41 and the spring terminal 42.

One end of the terminal plate 41 is a glass terminal 33
It is electrically connected to the socket 44 of the pin terminal 43, and the other end 41a is drawn out of the outer case 23.

Further, the spring terminal 42 is connected to a socket 46 of a pin terminal 45 of the glass terminal 33, which does not appear in FIG.
The other end 42a is electrically connected to the outer case 2.
3. Pulled out.

The induction motor starting protection device shown in FIG. 3 has an equivalent circuit shown in FIG. 4.

As shown in FIG. 4, a power supply G is connected between the tab-on terminal 38a conductive to the conductive plate 38 and the tab-on terminal 41a conductive to the terminal plate 41, and the spring terminal 4
If a phase advance capacitor C is connected between the tab-on terminal 42a and the tab-on terminal 41a which are electrically connected to the terminal 2,
A starting protection device for a PSC motor as shown in FIG. 5 is obtained.

Note that the starting protection device for the RSIR, CSIR, and CSR motors can also be configured by the device shown in FIG. 3.

If you do the above, overload relay 21
is placed between the motor 25 and the PTC thermistor element 22, and the overload relay 21 receives heat from both the motor 25 and the PTC thermistor element 22, so that the PTC thermistor element 22 and the overload relay 21 Together with the return of the thermally coupled positive temperature coefficient thermistor element 22, the overload relay 21 returns, and the motor 25 is reliably restarted.

In addition, the overload relay 21 is connected to the electric motor 25.
The heat generated by the heater 30 causes the bimetal 2 to
8 is activated, and the electric motor 25 can be reliably protected.

In FIG. 3, in order to improve thermal coupling between the overload relay 21 and the motor 25, the mounting surface of the outer case 23 to the motor 25 is opened, or a heat equalizing plate (see FIG. 3) is installed on the mounting surface. (Not shown.)
It is preferable to provide In addition, communication holes 50 and 50 are provided in the support portion 24a of the support member 24 of the overload relay 21 to allow the housing portions 39 and 40 to communicate with each other, thereby allowing heat between the overload relay 21 and the positive temperature coefficient thermistor element 22 to be communicated with each other. It is preferable to improve the bonding.

As is clear from the detailed description above, the present invention provides heat to the overload relay efficiently from both the motor and the positive temperature coefficient thermistor element in the conventional induction motor start-up protection device. The positive temperature coefficient thermistor element and the overload relay are thermally coupled, and the overload relay returns when the positive temperature coefficient thermistor element returns, allowing the motor to be reliably restarted. It operates and ensures the protection of the electric motor.

Furthermore, the overload relay can be used even if the operating temperature varies somewhat, and the cost of the start-up protection device can be significantly reduced.

Furthermore, in this invention, the overload relay and the positive temperature coefficient thermistor element are housed in a single exterior case as a plug-in type, which saves space, makes wiring easy, and is extremely easy to install on the motor. become.

[Brief explanation of drawings]

1 and 2 are explanatory diagrams of a conventional starting protection device for an induction motor, respectively, FIG. 3 is a sectional view of the starting protection device for an induction motor according to the present invention, and FIG.
Fig. 5 is an equivalent circuit diagram of a starting protection device for an induction motor, and Fig. 5 is a drive circuit diagram using a starting protection device for a PSC motor. 21... Overload relay, 22... Positive temperature coefficient thermistor element, 23... Exterior case, 24...
Supporting member, 25...Electric motor, 39, 40...Accommodating portion, 50...Communication hole.

Claims (1)

[Claims for Utility Model Registration] A positive temperature coefficient thermistor element and an overload relay are housed in one exterior case so that the overload relay is disposed between the induction motor and the positive coefficient thermistor element. In the starting protection device for an induction motor installed in a 1. A start-up protection device for an induction motor, characterized in that a communication hole is provided to communicate the housing parts with each other, and an opening is provided on a mounting surface of the overload relay to the induction motor that faces the housing part.