First of all, we need to know what is capacitor-switching contactor: this kind of contactor is specifically used to switch in/off power capacitor, it’s widely used in automatic reactive power factor compensation equipment, it’s applicable to the AC electrical network that is 50hZ, rated working voltage is up to 380V, the capacitor is up to 90kvar. This contactor is of building block type, the resistance circuit part is above the main circuit part, and the resistance circuit is three-way. The design of the main contact is reasonable, with independent load, offering reliable operation. After knowing this, we can see what differences between the capacitor-switching contactor and the common contactor.
1. Different applicable areas
A common contractor is used to control electrical motor, it can control electrical loads such as factory equipment, electric heater, operation mother machine, and various electrical appliance groups. Capacitor-switching contactor is used to switch in/off low voltage shunt power capacitors, widely used in automatic reactive power factor compensation equipment.
2. Different structures
Common contactor consists of an electromagnetic mechanism, contact system, arc extinguishing system, reaction device, bracket, and base. The switching capacitor contactor is composed of charging inrush suppression device and AC contactor. The action mechanism is direct-acting type, the contact is a double breakpoint, the magnetic system is E-shaped iron core, it coordinates with the reaction force for tower spring.
The capacitor-switching contactor is based on the common contactor, adding a contact module and suppression resistor that are intervened in advance to limit the maximum current of the contactor to 60In when it is switched on.
3. Different working theories
Common contactor: When the coil is powered on, the static iron core generates electromagnetic attraction, which makes the moving iron core be closed, then drives the three moving contacts of the contact system to act, the main contact is closed, the auxiliary NC contact is open, the auxiliary NO contact is closed, and the power supply is connected. When the coil is powered off, the electromagnetic attraction of the static iron core disappears, the reaction force of the spring makes the moving iron core and the static iron core separate, the three moving contacts act, which makes the main contact opens, the auxiliary NC contact closed, the auxiliary NO contact open, and the power supply cut off.
Capacitor-switching contactor: Large-capacity capacitor will occur a large charging current when it’s instantaneously energized, which makes the circuit occur overloaded instantly, and the overload will blow the fuse. The capacitor-switching contractor charges the capacitor through the current limiting resistor and then connects the power supply through the internal delay device, this way can reduce the large current impact of the circuit and prevent damage to the line fuse.
