The Time Mark 272-120 3-Phase Current Unbalance Detector monitors 3-phase lines to detect an unbalanced current. This model has a voltage range of 120VAC and a current input of 5A. It can also monitor three separate single phase lines for equal current levels.

The percentage of unbalance is adjusted from 2% to 25% by adjusting a front panel control. An unbalance greater than this setting energizes the relay. An adjustable trip delay of 0.5 to 10 seconds is also provided. For optimum performance, operating currents should be kept in the 1 to 5 amps range. However, zero current on each phase is considered to be a balanced condition.

Continuous currents, up to 10 amps per phase, will not damage the unit, nor will current surges up to 40 amps for 2 seconds. The contacts are automatically reset when the unbalanced condition is corrected.