Some people ask, if AC contactor coil is wrongly connected to equal voltage DC, or DC contactor coil is mistakenly connected to equal voltage AC, what will happen?

Let's first understand the difference between AC contactor and DC contactor.

1. The iron core structure is different.

AC contactor coil is connected with alternating current, which will produce eddy current. Therefore, the iron core of AC contactor is composed of silicon steel sheets with mutual insulation. In addition, 50 Hz AC will cross zero 100 times per second, and there is no current at zero point. Therefore, in order to solve the problem of zero point without suction force, a short circuit ring is added to the electromagnet core. The iron core of AC contactor is generally E type.

Iron core of AC contactor

The coil of DC contactor is supplied with direct current, so there is no eddy current and zero crossing. Therefore, the iron core is made of whole soft steel, which is generally U-shaped.

2. The number of coil turns is different.

AC contactor has less coil turns, larger wire diameter and larger current. The coil of DC contactor is slender and has many turns.

3. The operating frequency is different.

The AC contactor has large starting current and the highest operating frequency is 600 times / h. The operating frequency of DC contactor can be up to 2000 times / h.

4. Contact arc extinguishing device is different: AC contactor adopts grid arc extinguishing device, and DC contactor adopts magnetic arc extinguishing device.

According to the above differences, it can be analyzed that:

When the coil of AC contactor is connected with direct current, the coil will become a pure resistance load without inductive reactance, and the coil turns will be small, the resistance will be small, and the current will be large, which will cause the coil to heat up and burn out.

When the coil of DC contactor is connected to AC power: because the coil is slender, the number of turns is large, and the resistance is high, it can not be pulled in, or it can be put out when closing.

Electrician's correct understanding of normally open and normally closed AC contactor

The two most common words in the electrical industry are: normally open and normally closed. Learning electrician often starts with these two most basic words.

Many people often explain this: normally open means that it is disconnected under normal conditions, and it is disconnected when the coil is not powered on. Normally closed means that it is normally closed, and the coil is closed when it is not energized.

AC contactor 1, 3, 5 connected to three-phase power supply, (main circuit part)

2. 4 and 6 connected to three-phase motor

A1 and A2 are the coils of the contactor, which are connected to the control circuit. By controlling the coils (A1 and A2) of the contactor, the motor of the circuit part is controlled (small to large).

13. 14 represents the auxiliary contact of the contactor, and no indicates that it is normally open, that is to say, 13 and 14 are open when no power is applied, and 13 and 14 are closed after being electrified. It is placed in the control circuit part for self-locking (parallel on the start button) to achieve continuous operation.

But I don't think this explanation is comprehensive enough, and my buddies still can't understand it. For example, buttons and change-over switches have normally open and normally closed contacts, but they do not have coils. How can they get electricity?

Normally open: the letter identifies no, which is the abbreviation of the English word normal open. Normal: normal, normal and normal meaning. Open: open, open. Normal open literally means "disconnection" in normal circumstances. But here I think it should be: when the electrical components do not act, it means to disconnect, for example, when the contactor and relay do not pull in, and when the button is not pressed, it is disconnected. Once the contactor and relay are closed and the button is pressed, it will become closed.

Normally closed: the letter identifies NC, and the abbreviation of normal close means close and close. Normal close means that the contact is closed when the electrical component does not act. If the contactor does not pull in and the button is not pressed, the contact will be closed. Once the contactor is closed and the button is pressed, the contact will become disconnected.