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The Model 20AA is a microcontroller-based universal 3-phase monitor for protecting 3-phase motors from abnormal power conditions. It can detect under voltage, over voltage, voltage unbalance, reverse phase, and single-phasing even when regenerated voltage is present. The Model 20AA includes adjustable trip and restart delays to prevent nuisance tripping during power fluctuations and short cycling in compressor applications. The LED status indicators and adjustment pots for Voltage Adjustment, % Unbalance, Restart Delay and Trip Delay are mounted on the front of the unit for easy access. The 20AA has 2 normally open (N.O.) isolated contacts.

Automatic or manual restart versions are available. The Model 20AA does not require a neutral connection and can be used on either Wye or Delta systems.

All versions of the Model 20AA are UL Recognized (U.S. and Canada) and are available with optional gold flashed silver contacts for low current applications.

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Additional Information

Automatic Reset



UL (C and US)


2x N.O.

Manual Reset



DIN, Surface Mount

Phase Sensing

Phase Reversal,Phase Loss,Phase Unbalance

Trip Delay


Trip Restart


Voltage Sensing

Under Voltage Protection, Over Voltage Protection

Voltage Range