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Any place you find an electrical motor there's constantly a contactor to drive and run that motor. An electric contactor is merely an electrically controlled switch, likewise called a relay, utilized for switching a power circuit.

It is created so that when sufficient current circulations through a coil built into the contactor, the electromagnetic field which is produced causes the contacts to be pulled in. The contacts, in turn operate as the switch.

The contacts are appropriately sized by the designer of the circuit to manage current circulation without overheating. Contactors are offered in a variety of sizes for particular applications. The design of the contacts themselves allow the contactor to be opened and closed repeatedly with minimal damage. This, obviously can and will differ depending on the load present and failure can come rather rapidly to an incorrectly sized contactor.

Contactors are designed and integrated in two popular setups, single stage (or single pole) and 3 stage (three pole). This designation simply represents the variety of circuits that can be run at the same time. The coil is the means of running the contacts. When it is energized with an appropriate voltage, it produces enough magnetic force to pull the contacts into a closed position, or close the power circuit. When the coil circuit is opened, spring pressure returns the contacts into the employment opportunity threrefore opening the power circuit.

The most typical issue with a contactor, single or 3 phase would be an unsuccessful coil. This would trigger the contactor to cannot energize when voltage is being applied to the coil. It can be tested in two methods, initially in a power on circumstance, a check of the voltage at the coil terminals must provide a definite answer regarding whether the coil is energizing.

On contactors with overload resets you'll have to check the overload circuit of the contactor for failure or an open circuit if you do not read the proper voltage directly from the coil terminals. Of course you will need to validate the voltage with the label or nameplate on the coil. Any doubt as to your finding, you can inspect for coil continuity.

An open circuit (or high resistance) would represent an open coil whereas any moderate resistance would usually show that the coil is conducting electrical power. A reading of 0 ohms would indicate a brief circuit within the coil but this is unusual due to the fact that energizing a shorted coil typically amounts to excess heat, excess existing, and an ultimate opening of the coil internally.

The next most common failure is in the contacts themselves. They can fail in an open position, literally burned or melted open as a result of the contactor being improperly sized or the aftermath of a shorted load such as an overloaded motor. This can be checked by powering down the contactor circuit, both control and power circuit, and getting rid of the power leads from the load side of the contactor. Stimulate the coil control circuit and look for the proper voltage on the load terminals.

Correct voltage going into the contactor and lack of voltage going out of the contactor while it is energized or closed is a classic case of a failed contact. Another failure to the contacts would be a welded, or stuck contact which stays closed even when the contactor is de-energized. This circumstance can cause further issues or damage downstream in the circuit potentially by energizing a couple of legs of a three phase motor. With the control and power circuit de-energized this can be consulted an ohmmeter set on any range. A low ohm or 0 ohm reading would indicate a closed contact when in truth it must be open.

Additional contactor problems include mechanical failure such as in the return springs or the frame of the contactor and the majority of the time a visual evaluation suffices to find an issue such as this. These failures typically happen after extreme heating or after the operating or life span of the contactor has actually been gone beyond.

In general, the contactor troubleshooting is simple, yet an ignored failure within one of these crucial components can often confuse even an experienced electrician or upkeep professional.

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