© 2016 Littelfuse Protection Relays & Controls
Protection Relays
Voltage Monitoring Relays
www.littelfuse.com/50r
Rev: 1-A-062716
Description
The 50R Series single-phase voltage monitor has a voltage-
sensing circuit which constantly monitors the single-phase
power for a low voltage condition. Single-phase motors on fans,
compressors, air conditioners, heat pumps, well pumps, sump
pumps and small conveyor motors are all applicable to the
50R Series.
When a harmful condition is detected, the MotorSaver’s output
relay is deactivated after a specified trip delay. The output relay
reactivates after power line conditions return to an acceptable
level and a specified amount of time has elapsed (restart
delay). The trip delay prevents nuisance tripping due to rapidly
fluctuating power line conditions.
Features & Benefits
FEATURES BENEFITS
Proprietary voltage
sensing circuitry
Constant monitoring of single-phase power for a
low voltage condition
Adjustable trip delay
(-3 models) and restart
delay (-2 models) settings
Prevent nuisance tripping due to rapidly fluctuating
power line conditions and allows staggered start up
of multiple motors, after a fault, to prevent a low
voltage condition
High voltage detection
(-9 models)
Trips and resets at a fixed percentage of the
setpoint: trip 110%, reset 107%.
600V rated relay
contacts available
on some models
Eliminates the need for a control transformer to step
voltage down to 120 - 240V for a control circuit
Single-phase voltage monitor
50R SERIES
Wiring Diagram
50R
Ordering Information
MODEL LINE VOTAGE DESCRIPTION
50R-100 95-120VAC Fixed trip and restart delay
50R-100-2 95-120VAC Fixed trip and variable restart delay (manual, 2-300s)
50R200 190-240VAC Fixed trip and restart delay
50R2002 190-240VAC Fixed trip and variable restart delay (manual, 2-300s)
50R2003 190-240VAC Fixed restart and variable trip delay (2-30s)
50R20029 190-240VAC Fixed trip and variable restart delay (manual, 2-300s) plus high voltage detection
50R400 380-480VAC Fixed trip and restart delay
50R4002 380-480VAC Fixed trip and variable restart delay (manual, 2-300s)
50R4003 380-480VAC Fixed restart and variable trip delay (2-30s)
50R40029 380-480VAC Fixed trip and variable restart delay (manual, 2-300s) plus high voltage detection
