JPS60162415A - Overload protecting circuit of motor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to an overload protection circuit 1 for an electric motor.

[Technical background of the invention and its problems] For example, a nuclear power plant is equipped with an emergency reactor cooling system (hereinafter referred to as BCCB system), and the reactor cooling water flow path is controlled by opening and closing electric valves. This is ensured by In this case, even if the electric motor for opening and closing the electric valve becomes overloaded, the electric valve is forcibly opened and closed without stopping the electric motor.

This is due to the requirement to protect the nuclear reactor.

On the other hand, in the ECC8 system, periodic equipment function tests are required, and in the case of this electric valve unit test, overload protection of the motor for the electric valve is performed by the overload protection circuit t. However, if a signal that requires activation of the ECC8 system (hereinafter referred to as an accident signal) is detected during a unit test, the overload protection function of the electric valve motor is activated in order to protect the reactor as described above. It's designed so that it doesn't get any easier. Similar control circuits are still used for electric motors that drive equipment such as pumps.

Figures 1 and 2 are conventional circuit diagrams. To explain its operation, during normal operation, the control switch 4 is OFF and the relay 5 is not energized, so its contact 5b remains closed. It is.

Then, the power source 17 for the contactors 15 and 16 is supplied regardless of the excitation of the relay 3, resulting in a circuit that bypasses the overload relay 2.

On the other hand, when testing the function of a single electric valve, the control switch 4 is turned on. If the contact 8b of the relay 8 is closed, the relay 5 is energized and the contact 5b is opened.

Therefore, the power supply 17 of the contactor 15 and the contactor 16 is opened and closed by the contact 3b of the relay 3, so that the function of the overload relay 20 is activated.

During this functional test, if the gccs system is required to operate,
Limit switch 6 is turned on and relay 7 is energized.

Then, the contact 7a is closed and the relay 8 is energized.

Then, the contact 8b is opened, so the relay 5 is de-energized and the overload relay 2 is bypassed.

By the way, in the ECC8 series, in addition to the functional test of the electric valve alone,
In addition, system maintenance tests are also required to ensure that the devices that make up the system and the logic that controls them function properly. In this case, a simulated accident signal is input from the test signal input connector 9. Therefore, in this case, the relay 8 may be energized and the function of the overload relay 2 may be bypassed in the same operation as when the above-mentioned fault signal is generated.

For this reason, in the conventional system, maintenance testing of the system, that is,
The simulated accident signal, rather than the actual accident signal, bypasses the protection function of the electric valve motor. For this reason, even in a simple test, the electric motor is overloaded and forced into operation. This shortens the life of the electric motor, which in turn greatly affects the operating rate of the plant.

[Purpose of the invention]

The present invention makes use of the conventional thermal bypass circuit during normal plant operation and in the event of an accident, and during system maintenance tests.
The purpose is to provide the function of an overload protection circuit to prevent motor burnout due to overload with test signals.

[Summary of the Invention] In order to achieve this object, at the same time as a simulated fault signal is input during a system maintenance test, a signal contact that is inputting a simulated signal is connected to an overload protection control circuit, and the contact is used to simulate the failure signal during the system maintenance test. is characterized by an overload protection circuit.

Examples of the present invention] Examples of the present invention will be described below. FIG. 1 is a circuit diagram of an overload relay section of a motor for an electric valve as described above, and an overload relay 2 is provided to protect the motor 1 from overload. When the motor 1 becomes overloaded, this overload relay 2
The operation of operation b causes the relay 3 to be energized. In other words, the power supply 1 for the power supply 15 and 16 for the power supply contactor 15 and 16 for the motor 1 is
7 is opened and closed by contact 3b or contact 5b.

FIG. 3 is a diagram of a motor overload protection circuit of the present invention with additional signal contacts during system maintenance tests. When the limit switch 6 for detecting the accident signal is detected, the temperature rises and the V-7
is excited. When relay 7 operates, its contact 7a closes, so relay 8 acts as an amplification contact and coil L 220
works. That is, when an actual accident signal is input during the test, the protection function is bypassed. During a system maintenance test, that is, when a simulated accident signal is input through the connector 9, the relay 8 operates and its contact 8b opens, but the relay 10 also operates and its contact 10a closes. Therefore, the relay 5 remains in its operating state. That is, the overload protection function is not bypassed.

Assume that the control switch 4 is now closed to perform a functional test of the valve alone. Then, when a simulated trip signal is input through the system maintenance test connector 9, the relays 8 and 10 operate. This causes contact 1
Since 0a is closed, the relay 5 is in an excited state. When the relay 5 is energized, its contact 5b is opened. Here, when the electric motor 1 becomes overloaded and the overload relay 2 operates, the relay 8 is excited and its contact 3b is opened.

Since the contacts 5b and 3b of the power source 17 of the electric motor 1 are open, the power is turned off, that is, both the contactors 15 and 16 are opened, so the electric motor 1 is stopped and overload protection is achieved.

At times other than system maintenance tests, no simulated signal is input to the converter 9, so the relay 10 is de-energized and its contact 10a is also open. In other words, overload protection is bypassed during normal operation.

〔Effect of the invention〕

As described above, according to the present invention, even if a simulated trip signal is input during a plant system maintenance test, it is useless because the overload protection function in the motor control circuit is satisfied and the motor is protected. damage to the electric motor can be prevented.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of an overload relay section of an electric valve motor, FIG. 2 is a conventional overload protection bypass control circuit diagram, and FIG. 3 is an overload protection bypass control circuit diagram after the invention. J... Electric motor 2... Overload relay kite 3.5, 7.8.10... Relay 4... Control switch 6... Accident trip signal contact 9... Connector 15.16...・Contactor 17
...Contact power supply Fig. 1/ Fig. 2 Fig. 3 Wl

Claims (1)

[Claims] When testing a single motor, the overload protection function is activated to prevent the motor from being overloaded, and when testing a system in which the motor is installed, the overload protection function is excluded, and during the single test of the motor, the overload protection function is activated to prevent the motor from being overloaded. When an accident signal of ζ is input, the overload protection function is excluded. An overload protection circuit for an electric motor, characterized in that the overload protection function is excluded when the actual accident signal is input during the test.