JPS581524B2 - Operation circuit of DC operation electromagnet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention applies to repeated operations (called pumping operations) of, for example, electromagnetic contactors.

) This relates to an operating circuit for a DC operating electromagnet having a prevention function.

Figure 1 shows a conventional operating circuit, where 1 is an operating switch connected to a power source, and 2 is an auxiliary contact set to open from the closed state immediately before the suction operation of the movable iron core is completed. , 3 is a resistor called a saving resistor, and 4 is a closing coil.

In the case of electromagnetic contactors, etc., in a no-voltage state, the movable core is
It is in the open state due to the trip spring.

When the switch 1 is opened, the closing coil 4 is energized, the movable core is attracted, and the contactor performs the closing operation.

At this time, just before the suction operation of the movable iron core is completed, the auxiliary contact 2 is released from the closed state, and the auxiliary contact 2 and the resistor 3 connected in parallel are inserted in series with the closing coil 4. The current flowing through the coil 4 is limited to the holding current in the closed state as shown in a in FIG. 4, and the closing operation is completed.

However, setting the position of the opening operation of the auxiliary contact 2 requires very strict dimensional accuracy, and the normal operating position is 0.
Only about 3 to 0.7 h is allowed.

In other words, if the auxiliary contact 2 operates too quickly, the current flowing through the closing coil 4 decreases while the movable core is not yet sufficiently attracted, resulting in a large magnetic resistance in the magnetic circuit and the current flowing through the closing coil 4, which is required to complete closing. As a result, the movable core is pushed back by the trip spring, and the main contact of the contactor, which was once closed and closed, is opened.

When the movable core is pushed back, the auxiliary contact 2 is closed again, so the current in the closing coil 4 increases and attracts the movable core, but as mentioned above, the closing cannot be completed and the movable core ends up This will result in repetitive movements (pumping movements),
The main contact of the contactor repeats closing and opening.

In addition, if the operation of the auxiliary contact 2 becomes slow, the auxiliary contact 2 will not open even though the movable core has been attracted, and an excessive current that is more than necessary will continue to flow through the closing coil 4. This causes the input coil 4 to overheat and burn out.

As described above, the resistance 3 is
In the method of inserting the auxiliary contact 2, it is necessary to set and manage the operating position of the auxiliary contact 2 with high precision, and there is also the disadvantage that similar problems may occur due to positional deviation of the auxiliary contact 2 or contact wear that occurs during use. Ta.

The purpose of this invention is to prevent malfunctions due to misalignment of the auxiliary contact and contact wear by widening the allowable dimensions for setting the operating position of the auxiliary contact, thereby ensuring reliable operation of the contactor and improving its reliability. be.

FIG. 2 is a circuit diagram showing an embodiment of the present invention.
4 is exactly the same as the conventional device described above.

5 is a capacitor connected in parallel with the auxiliary contact 2 and the resistor 3.

In this circuit, during suction operation of the movable iron core, auxiliary contact 2
When the coil is opened from the closed state, a resistor 3 is applied to the closing coil 4.
A parallel circuit of capacitor 5 and capacitor 5 is inserted in series.

Simultaneously with the opening of the auxiliary contact 2, a charging current flows to the capacitor 5 with a time constant T [seconds] - C (F) x R (Ω), [C - capacitor capacity, R - DC resistance of the input coil].
After charging is completed, the current of the closing coil 4 is limited by the resistor 3 so that the current is maintained in the closing state, and the closing operation is completed.

By selecting the capacitance of capacitor 5 to an appropriate value,
The sudden decrease in the current in the closing coil 4 that occurs when the auxiliary contact 2 is opened is compensated for by the charging current in the capacitor 5, resulting in a current waveform as shown in b in Figure 4. There is no reduction in suction force, and even if the opening device of the auxiliary contact 2 is set to a position where it operates quickly, the repetitive motion (bombing motion) of the movable core does not occur and can be completely prevented. I can do it.

The capacitor 5 is charged to a voltage divided by the resistance values of the resistor 3 and the closing coil 4, but when the switch 1 is opened, the closing coil 4 is deenergized and the movable iron core is pulled back by the tripping spring. The auxiliary contact 2 performs a return operation after closing, and the capacitor 5 is short-circuited and the charged electric charge is discharged.

Generally, the closing speed of an electromagnetic contactor, etc. (i.e., the suction speed of the movable iron core) is set to 0.2 to 1 m/see, and in order to increase the allowable dimension of the operating position of the auxiliary contact 2 by 21 m, for example, The capacity of the capacitor 5 is selected so that the charging current of the capacitor 5 necessary for suction flows for a time of 10 ms to 27 ms.

That is, the capacitance of the capacitor 5 may be selected so that the product of the resistance R of the input coil 4 and the capacitance C of the capacitor 5 becomes an appropriate value.

The inventors obtained good results with a capacitor capacity of 20 [μf] in an input coil with a coil resistance of 170 [Ω], and were able to widen the allowable dimension for setting the operating position of the auxiliary contact 2 by two dragons.

It goes without saying that this capacitor 5 is also effective in eliminating sparks from the auxiliary contact 2 due to its operating principle.

In Figure 3, a resistor 6 is connected in series with the capacitor 5 to limit the rush discharge current of the capacitor 5 flowing to the auxiliary contact 2 when the switch 1 is opened and the auxiliary contact 2 is closed again. In addition, when this resistor 6 restricts the charging current of the capacitor 5 during the suction operation of the movable iron core, that is, when the auxiliary contact 2 is opened, and this causes a problem in preventing the repetitive operation (bombing operation) of the movable iron core, this resistor 6 is used. A diode 7 is connected in parallel with 6 to conduct in the charging direction of the capacitor 5.
When the capacitor 5 is charged, the resistor 6 is short-circuited.

In the above description, the present invention has been described with respect to an electromagnetic contactor, but it may also be used in a circuit breaker or an electromagnetic relay that performs a similar operation.

As explained above, the present invention has the effect that repetitive motion (bombing motion) of the movable iron core can be prevented by connecting a capacitor to a resistor connected in parallel with the auxiliary contact.

[Brief explanation of drawings]

Fig. 1 is an operating circuit diagram of a conventional device, Fig. 2 is an operating circuit diagram showing one embodiment of the present invention, Fig. 3 is an operating circuit diagram showing another embodiment of the present invention, and Fig. 4 is a closing coil diagram. 5 is a waveform diagram showing four current waveforms and a terminal voltage waveform of a capacitor 5. FIG. In the figure, 1 is a switch, 2 is an auxiliary contact, 3 is a resistor, 4 is a closing coil, 5 is a capacitor, 6 is a resistor, and 7 is a diode. Note that the same reference numerals in each figure indicate the same parts.

Claims (1)

[Claims] 1 Connected to a closing coil connected to a power source and a movable core that is attracted by the energization of this closing coil. In the operation circuit of the DC operation electromagnet, the operation circuit includes a series body with a contact that operates from a closed state to an open state immediately before the suction operation of the movable iron core is completed, and a resistor connected in parallel with the contact. 1. An operating circuit for a DC-operated electromagnet, characterized in that a capacitor having a capacitance set such that the product of the DC resistance of the input coil becomes a predetermined value is connected in parallel with the contact and the resistor.