NewTrend · Three-phase undervoltage monitoring relay
Product overview
NewTrend RV8-4UVS monitors the three phase-to-neutral voltages in a three-phase system with neutral using true-RMS measurement. The undervoltage threshold is 70%-95% of nominal voltage, adjustable. A 0.1-second trip delay disconnects the control output after undervoltage, while an adjustable 5-15 minute delay applies at power-up and after voltage recovery. One SPDT output rated 10A AC-1 controls a suitable external contactor.
Technical selection summary
| Model | RV8-4UVS |
|---|---|
| Function | Undervoltage monitoring |
| Phase system | Three-phase + neutral |
| Monitoring terminals | L1-L2-L3-N |
| Supply terminals | L1-N |
| Nominal voltage options | AC 220V / AC 230V / AC 240V |
| Supply frequency | 45-65Hz |
| Measurement | True RMS |
| Measurement error | Maximum 1% |
| Undervoltage threshold | 70%-95% of nominal voltage, adjustable |
| Trip delay Tu | 0.1 seconds |
| Hysteresis | 5V |
| Power-on delay Td | Adjustable 5-15 minutes |
| Recovery delay Tr | Adjustable 5-15 minutes; Td = Tr |
| Knob-setting accuracy | 10% of scale value |
| Supply / delay indication | Green LED |
| Output indication | Red LED |
| Output contacts | 1 SPDT |
| Contact rating | 10A (AC-1) |
| Switching voltage | 250VAC / 24VDC |
| Mechanical life | 10,000,000 operations |
| Electrical life (AC-1) | 100,000 operations |
| Operating temperature | -20 to +55 degrees C |
| Storage temperature | -35 to +75 degrees C |
| Mounting | DIN rail to EN/IEC 60715 |
| Protection | IP40 front panel; IP20 terminals |
| Operating position | Any |
| Overvoltage category | III |
| Pollution degree | 2 |
| Maximum conductor size | Solid: 1 x 2.5mm2 or 2 x 1.5mm2; with sleeve: 1 x 2.5mm2 (AWG 12) |
| Terminal tightening torque | 0.8Nm |
| Body dimensions | 90 x 18 x 64mm |
| Referenced standards | EN 60255-1; IEC 60947-5-1 |
Select the nominal phase-to-neutral supply voltage to match the installation. A neutral connection is required; this model is specified for undervoltage monitoring, without an unsupported phase-sequence or overvoltage claim.
Operation
- At power-up, the relay waits for the selected delay Td before enabling the output when voltage is normal.
- If the monitored voltage falls below U<, the output trips after 0.1 second. After the voltage recovers through the hysteresis band, the selected recovery delay Tr runs before output re-enabling; Td = Tr.
Typical applications
- Undervoltage control of air-conditioning and other inductive equipment through a contactor
- Delayed restart after recovery from a low-voltage condition
Specify your enquiry
For a focused quotation, include:
- Nominal phase-to-neutral voltage: AC 220V, AC 230V or AC 240V
- Required adjustable threshold and restart delay, load and contactor details
- Quantity and delivery destination
Download NewTrend RV8-4UVS datasheet (PDF)
Product reference images and drawings
Terminal connections
Undervoltage trip and delayed recovery
Common housing dimensions; RV8-4UVS front view shown.
Three-phase contactor-control reference
Set the common power-on/recovery delay t from 5 to 15 minutes; Td equals Tr. Set U< between 70% and 95% of nominal voltage. The native waveform shows the 5V hysteresis and relay behavior during a voltage dip. Installation and wiring must be performed by qualified electricians.
