JPH03212196A - Control circuit for electromagnetic contactor - Google Patents

Abstract

PURPOSE:To prevent erroneous function of an auxiliary relay by connecting a resistor, having impedance equal to or lower than the coil impedance of the auxiliary relay, in parallel with the auxiliary relay. CONSTITUTION:A resistor 7 is connected in parallel with an auxiliary relay 3, where the resistance R of the parallel resistor 7 is selected equal to or lower than the inner impedance of the auxiliary relay 3. Under stop state, where a stop command switch 5 is turned OFF by this parallel circuit, current io flowing through the internal circuit of an electronic instantaneous stop restart relay 6 to the circuit of the auxiliary relay 3 is branched into a current i1 flowing through a relay coil and a current i2 flowing through the parallel resistor 7. Consequently, voltage across the operating coil of the auxiliary relay 3 drops below a specified release voltage resulting in a reliable OFF function of an electromagnetic contactor.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a control circuit for an electromagnetic contactor used to control the operation of electric motors installed in various industrial plants.

[Conventional technology]

In industrial plants, as a momentary power outage protection measure for electric motors, etc., when the power supply voltage of the main circuit temporarily drops or is lost and then recovers immediately, in order to maintain operation of the plant equipment, the equipment is switched off at the same time as the power supply voltage is restored. A low-voltage release method for restarting is often used.

Here, taking an electric motor as an example, FIG. 2 shows a conventional example of an operation control circuit for an electric motor using the above-mentioned low voltage release method. 3 is a magnetic contactor auxiliary relay (88K), 4.5 is a run/stop command switch, and 6 is an electronic instantaneous restart relay with a built-in microcomputer.

With this circuit, the electric motor 1 is operated by the operation command switch 4. Operation and stop are controlled by operating the stop command switch 5. Also, there was a power outage while the motor was running.

In the event that the power supply voltage temporarily drops or is lost due to a malfunction or the like and is immediately recovered, the electronic instantaneous power failure restart relay 6 is activated and the magnetic contactor 2 is activated at the same time as the power supply voltage is restored. Close it and restart the electric motor 1.

On the other hand, as the auxiliary relay 3 of the electromagnetic contactor 2 used in combination with the electronic instantaneous restart relay 6 as described above, the recent trend is to replace the conventional auxiliary relay with a low internal impedance of the relay coil.

High impedance type relays, commonly called mini control relays, which have large impedance (about IOK to 2 OKΩ) are widely used.

[Problem to be solved by the invention]

By the way, if a high impedance type relay is used as an auxiliary relay in a magnetic contactor control circuit, such as the motor operation control circuit shown in Figure 2, the following malfunctions may occur in terms of control operation. It may cause

In other words, in a circuit constructed by combining the auxiliary relay 3 with the electronic instantaneous restart relay 6 as shown in FIG. A small current io flows through the operating coil of the auxiliary relay 3 through the internal circuit indicated by the dotted line. For this reason, especially if the auxiliary relay 3 is a high impedance type relay, the relay will not release, and as a result, even though the electric Ill has given a stop command, the electromagnetic contactor 2 will not switch off and stop. do not.

The present invention has been made in consideration of the above points, and an object of the present invention is to provide a control circuit for an electromagnetic contactor that can prevent the above-mentioned auxiliary relay from malfunctioning by adding a small number of circuit components. do.

[Means to solve the problem]

In order to solve the above problems, the present invention provides a control circuit for an electromagnetic contactor that combines an electronic instantaneous restart relay, a high impedance type auxiliary relay, and a run/stop command switch. , a parallel resistor having an impedance value equal to or lower than the coil impedance of the auxiliary relay shall be connected.

[Effect]

In a circuit in which a parallel resistor is connected to the auxiliary relay as described above, when the control circuit is stopped, the current flowing to the auxiliary relay's operating coil through the electronic instantaneous restart relay is shunted to the parallel resistor, and the auxiliary relay's operating coil is It works to reliably lower the voltage between the terminals to below the release voltage of the relay, thus preventing the electromagnetic contactor from malfunctioning in a stopped state.

〔Example〕

FIG. 1 shows a control circuit diagram of an embodiment of the present invention,
Identical parts corresponding to FIG. 2 are given the same reference numerals.

In FIG. 1, the control circuit of the electromagnetic contactor 1 is basically the same as that in FIG. 2, but according to the present invention, a parallel resistor indicated by the reference numeral 7 is connected to the auxiliary relay 3. The resistance R of this parallel resistor 7 is selected to have an impedance value equal to or less than the internal impedance of the auxiliary relay 3.

With this circuit, in the stopped state with the stop command switch 5 turned off, the amount of current 〇 flowing into the circuit of the auxiliary relay 3 through the internal circuit of the electronic instantaneous restart relay 6 is equal to the current i1 passing through the relay coil and the parallel resistance 7. The current passing through i is divided into two parts. Therefore, the voltage between the terminals of the operating coil of the auxiliary relay 3 drops below the specified release voltage, thereby ensuring that the electromagnetic contactor 1 is turned off.

〔Effect of the invention〕

As described above, the present invention is a control circuit for an electromagnetic contactor used for controlling the operation of an electric motor, etc., and includes an electronic instantaneous restart relay, a high impedance type auxiliary relay, and a control circuit for controlling the operation of an electric motor.
In a combination of stop command switches, even though a stop command has been given because a parallel resistor with an impedance value equal to or lower than the coil impedance of the auxiliary relay is connected to the auxiliary relay. It is possible to reliably prevent malfunctions in which the auxiliary relay does not release and therefore the electromagnetic contactor does not turn off.

[Brief explanation of drawings]

Claims (1)

[Claims] 1) A control circuit for an electromagnetic contactor used to control the operation of electric motors, which combines an electronic instantaneous restart relay with a high-impedance auxiliary relay, and a run/stop command switch. On the other hand, a control circuit for an electromagnetic contactor characterized in that a parallel resistor having an impedance value equal to or lower than the coil impedance of the auxiliary relay is connected.