Pros, Join Our TradeMaster Program!
The 250A is a 3-phase, auto-ranging, dual-range voltage monitor that protects 190-480VAC, 50*/60Hz motors regardless of size from low and high voltage, unbalance/single-phase, and reverse-phase. The product provides a user selectable nominal voltage setpoint and the voltage monitor automatically selects between the 200V and 400V range. The 250A also features adjustable or manual restart delay.
This unique microcontroller-based voltage and phase-sensing device constantly monitors the 3-phase voltages to detect harmful power line conditions. When a harmful condition is detected, the Littelfuse’s output relay is deactivated after a specified trip delay. The output relay reactivates after power line conditions return to acceptable levels. The Model 250A includes advanced single LED diagnostics. Five different light patterns distinguish between faults and normal conditions.

  • Input Voltage (V): 190 to 480VAC
  • Maximum Input Power: 5W
  • Input AC Line Frequency (Hz): 50/60Hz (50Hz will increase all delay timers by 20%.)
  • Output Form: DPDT - 2 Form C
  • Output Load Rating (VA); Pilot Duty: 480VA @ 240VAC B300; General Purpose: 10A @ 240VAC
  • Restart Delay Range: Manual 2 - 300s adjustable
  • Trip Delay Range: Under/Over Voltage: 4s; Unbalance Phasing Faults: 2s
  • Trip Point Accuracy (%): ±1%
  • Overvoltage Trip Voltage (%): 110%
  • Overvoltage Reset Voltage (%): 107%
  • Undervoltage Trip Voltage: 90%
  • Undervoltage Reset Voltage (%): 93%
  • Voltage Unbalance Trip Point (%): 6%
  • Voltage Unbalance Reset (%): 4.50%
  • Termination Type: Torque: 7in-lbs; Wire: 12-18AWG
  • Mounting Method: #8 screws
  • Operating Temperature: -40° to 70°C (-40° to 158°F)
  • Humidity: Up to 95% non-condensing per IEC 68-2-3
  • Dimensions: 2.93 in H x 5.27 in W x 2.95 in D (94.4 x 133.9 x 74.9 mm)
Hide Description
Product Type:

Voltage Meter




Form C



Product Reviews

Product Q&A

Add-on Item

This item is cost-prohibitive to ship on its own but is available to ship with orders over $200.

Why don't we show the price of this item?

We try to always offer you the lowest prices possible, but some manufacturers require that we only show these low prices once you take further action.

To see the price, simply add the item to your cart or sign in.