Littelfuse PLMU11, PLMU Serie, Voltage Sensing AC 200 ~ 480VAC, SPDT (1 Form C), Octal 8-pin plug-in Termination
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The PLMU11 continuously measures the voltage of each of the three phases to provide protection for 3-phase motors and sensitive loads. Its microcontroller senses under and overvoltage, voltage unbalance, phase loss, and phase reversal. Protection is provided even when regenerated voltages are present. Universal voltage operation and standard base connection allows the PLMU11 to replace hundreds of competitive part numbers.
Operation
Upon application of power, a 0.6s random start delay begins and the PLMU11 measures the voltage levels and line frequency and selects the voltage range. The output relay is energized and the LED glows green when all voltages are acceptable and the phase sequence is correct. LED flashes green during trip delay, glows red when output de-energizes. Undervoltage, overvoltage, and voltage unbalance must be sensed for continuous trip delay before the relay de-energizes.
Re-energization is automatic upon fault correction. The output relay will not energize if a fault condition is sensed as 3-phase input voltage is applied. The LED alternately flashes red/green when phase reversal is sensed. Line voltage is selected with the knob, setting the over and under voltage trip points. Voltage range is automatically selected by the microcontroller
| Line Voltage | |
| Type | 3-phase delta or wye with no connection to neutral |
| Line Voltage | 200 to 480VAC ±15%, 50/60 Hz ±2 Hz |
| Adjustable Voltage Ranges (Automatic Range Selection) |
200 to 240VAC, 50/60 Hz 340 to 420VAC, 50 Hz 400 to 480VAC, 60 Hz |
| Maximum Voltage | 552VAC |
| Phase Sequence | ABC |
| Power Consumption | ≤ 5W |
| Overvoltage, Undervoltage, & Voltage Unbalance | |
| Type | Voltage detection with delayed trip and automatic reset |
| Overvoltage & Undervoltage |
Undervoltage Trip Point 88 - 92% of adjusted line voltage Reset Voltage +2% of trip voltage Overvoltage Trip Point 109 - 113% of adjusted line voltage Reset Voltage -2% of trip voltage |
| Voltage Unbalance Trip Point Reset on Balance (%) | Adjustable from 2 - 10% |
| Selected Unbalance | 2 3 4 5 6 7 8 9 10 |
| Reset | 1.5 2.5 3.5 4.5 5.4 6.3 7.2 8.1 9 |
| Trip Delay Range | Adjustable from 0.25 - 30s |
| Severe Unbalance - 2X Selected Unbalance | 0.25 - 2s; disabled when the trip delay is less than 2s |
| Random Start Delay | ≅ 0.6s |
| Phase Reversal & Phase | |
| Loss Trip Time | ≤ 150ms |
| Phase Loss Setpoint | ≥ 15% unbalance |
| Reset Type | Automatic |
| Output Type | Energized when voltages are acceptable |
| Type | Electromechanical relay |
| Form | Isolated, SPDT |
| Rating |
10A resistive @ 240VAC; 1/4 hp @125VAC; 1/3 hp @ 250VAC; max. 277VAC |
| Life | Mechanical - 1 x 10⁶ ; Electrical - 1 x 10⁵ |
| Protection | |
| Surge | IEEE C62.41-1991 Level B |
| Isolation Voltage | ≥ 2500V RMS input to output |
| Mechanical | |
| Mounting* | Plug-in socket rated 600VAC |
| Termination | Octal 8-pin plug-in |
| Dimensions |
H 77.0 mm (3.03”) W 60.7 mm (2.39”) D 45.2 mm (1.78”) |
| Environmental | |
| Operating/Storage Temperature | -40° to 60°C / -40° to 85°C |
| Weight | ≅ 8.6 oz (244 g) |