Model 250A is an auto ranging voltage monitor designed to protect 3-phase
motors regardless of size. It is used on 190-480VAC, 50 to 60 Hz motors to
protect the motors from damage caused by single phasing, low voltage,
phase reversal, voltage unbalance, and also high voltage. Added features
include the DPDT contacts that are used to perform two functions when
parameters are exceeded in addition to the standard adjustable restart delay.