The 3620 thermal relay from E-T-A Circuit Breakers is a novel device that
is capable of simultaneously disconnecting all three phases of a
three-phase motor installation in the event of overheating in the
windings. All four poles of the relay are disconnected simultaneously and
within 30s of a motor winding over-temperature condition. Instead of
requiring additional electronics to break the second and third phases and
to provide a separate signal indicating the action, the 3620's four-pole
architecture provides for the three phase disconnections plus a fourth
closure for status indication. The unit is rated for auxiliary circuit
currents of up to 10A per phase at 400V ac. Two versions are available,
one with integral manual reset, the other with automatic time delay reset.