Pull-In and Hold-In Current

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The coils for each relay can be connected to an electronic circuit board or they can be connected with switches to make a motor control circuit. The main point to remember is that the voltage used to energize the coil should match the coil rating. Just as in the coil of a solenoid, the amount of current that the coil uses when it's first energized and pulls in will be larger than the hold-in current. The pull-in current may also be called the inrush current and it's a rating that's normally listed in the relay specifications. The inrush current is generally three to five times larger than the hold-in current, which may be called the seal-in or sealed current, and it will also be listed in the specification for the coil. The diagram for pull-in and hold-in current for a relay coil is similar to the example of pull-in and hold-in current for solenoids shown previously (see below).

pull-in & hold-in current for solenoidss

Some specifications list the coil current ratings in volt-amperes (VA). VA is calculated by multiplying the voltage by the current, and keep in mind that this rating is the apparent power for the circuit. The wattage for a relay coil will be slightly lower and it can only be measured with a watt-meter.

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