HIU - Hold in Unit

Restart Relays, for Automatic Re-Starting of Motors After Voltage

Dips Despite disturbances in the power supply, minimizing plant

down time and ensuring maximum continuity of operation, is

essential in most modern industrial processes and systems,

The Hold-In Unit provides a controlled restart signal to automatically

restart critical motors that have tripped due to a voltage dip.

The restarting will be immediate or delayed depending on the

voltage dip duration.

Immediate Restarting

When dip < 100 mSec. (Immediate restarting is possible as motor's

slippage will not have increased beyond the point where undesirable

inrush currents would occur.)

Delayed Restarting

When dip 0.1 - 4 sec as the restored power supply may be in phase

opposition to the Back EMF generated by the motors.

Restarting will be delayed 1-30 Sec. until the residual Back EMF has sufficiently diminished.

Staggering the restarting of the motors prevents simultaneous restarting of all motors, which

can result in undesirable inrush currents.

No Restarting

When dip > 4 sec. for safety reasons.