Flowserve UEX Limitorque - Manual (Page 26)

Limitorque UEX FCD LMENIM1205-03-AQ – 05/15
26
7
Protection Features
7.1 Autophase Protection and Correction
The phase rotation of the incoming three-phase supply is continuously monitored. In the event that field
wiring is reversed, UEX controls automatically correct to ensure the valve operates in the commanded
direction. In addition, the detector circuit monitors the presence of all three phases. If a phase is lost,
valve starting will be prevented and the user alerted via an LCD error message and Monitor Relay Alarm.
7.2 Jammed Valve Protection
If the actuator cannot overcome the required valve starting torque, a jammed valve condition occurs.
Jammed valve protection senses the lack of valve movement and initiates a brief reverse/forward cycle
to free the valve. If this is unsuccessful, further electrical operation is prevented and the monitor relay is
signaled.
7.3 Instantaneous Reversal Protection
The control logic incorporates a brief time delay (from 0.5 to 1.0 seconds) between motor reversals.
This reduces motor current surges and prolongs the life of the contactor. Note: It is not necessary to
switch to STOP before reversing the actuator.
7.4 Motor Thermal Protection
The motor is protected against overheating by a thermal OL in the motor enclosure. Thermal cutout
threshold is set for 120˚C (Class B). Options are available for other classifications.
a CAUTION: Confirm that motor thermals are rated no higher than 120°C for Explosionproof service.