MV Systems

Vacuum Contactor


A contactor is an electrically controlled switch used for switching an electrical power circuit, similar to a relay except with higher current ratings. A contactor is controlled by a circuit which has a much lower power level than the switched circuit. Vacuum contactors utilize vacuum bottle encapsulated contacts to suppress the arc. This arc suppression allows the contacts to be much smaller and use less space than air break contacts at higher currents. As the contacts are encapsulated, vacuum contactors are used fairly extensively in dirty applications, such as mining. Vacuum contactors are only applicable for use in AC systems.

The AC arc generated upon opening of the contacts will self-extinguish at the zero-crossing of the current waveform, with the vacuum preventing a re-strike of the arc across the open contacts. Vacuum contactors are therefore very efficient at disrupting the energy of an electric arc and are used when relatively fast switching is required, as the maximum break time is determined by the periodicity of the AC waveform.


S.no Description
1 Checking & cleaning of Insulators, Partitions, shrouds & Panel interior
2 Cleaning & Lubrication of drive mechanism as per manual
3 Cleaning & Lubrication of wheel as well as moving parts of breaker truck & Interlocking plate.
4 Cleaning & Lubrication of shutter mechanism, Door hinges and locks
5 Checking the Door, Bkr Truck & Earth Sw./Earthing truck interlocks functional
6 Checking and if required adjust allignment for smooth movement of CB truck
7 Checking Tightness of busbar & cable connection by Torque Wrench (For pnls)
8 Checking Tightness of Bolts in Drive Mechanism & Pole assy by Torque Wrench
9 Checking electrical operation of Tripping and Closing Coils.
10 Checking Tightness of control wiring at Terminals.
11 Checking position of coding pins of control plug, if applicable
12 Checking Mechanical operation of breaker by manual spring charging
13 Checking Draw-out male-female isolating power contact and if required clean & apply grease.
14 Checking healthiness of vaccum & Contact Erosion.
15 Checking healthiness of space heater & Thermostat.
16 Checking status of control fuses.
17 Checking of Earthing connection.
18 Breaker operation counter reading.
19 IR Values of Bkr(isolated)using 5KV megger. - in ON Pos. R-E/Y-E/B-E/R-Y/Y-B/B-R - in OFF Pos. R-R/Y-Y/B-B
20 Visual check of Gaskets.
21 Checking LT chamber illumination lamp
22 General Checking of breaker & panel for any abnormal condition
23 Millivolt Drop Test across Switching Contacts & at draw out contacts