To meet the global industrial market's demand for efficient and reliable motor protection, ONESTO introduces the Three-Phase Sequence Protector — MRVX7. Specifically designed for three-phase motors, the MRVX7 effectively prevents damage caused by voltage imbalance and phase loss. It also supports automatic recovery functionality to ensure stable motor operation, greatly extending equipment lifespan.

What is a Three-Phase Sequence Protector?

A three-phase sequence protector is an electrical protective device used for three-phase motors. Its primary function is to monitor whether the three-phase power supply has the correct phase sequence and balanced phase voltages, thereby protecting the motor from damage caused by phase loss, incorrect phase sequence, or voltage imbalance.

Working Principle:

By detecting the voltage difference and phase sequence of the three-phase power supply, if the voltage difference exceeds the preset threshold or the phase sequence is incorrect, the protector will automatically disconnect power after a 4-second delay to prevent motor damage. When the voltage difference returns to normal and the phase sequence is correct, the protector automatically restores power supply and indicates the operating status via indicator lights, achieving effective protection and automatic control of three-phase motors.

About ONESTO MRVX7:

Voltage Difference Protection and Recovery:

Trip Condition: When the voltage difference between any two phases exceeds 55V, the protector trips and disconnects, shutting down the motor for protection.

Delay Function: Equipped with a 4-second disconnection delay to prevent accidental motor shutdown due to transient voltage drops.

Automatic Recovery: When the voltage difference between any two phases recovers to within 50V, the motor automatically reconnects.

Phase Sequence and Phase Loss Protection:

Phase sequence and phase loss protection:

Phase Sequence Error/Phase Loss Indication: If the phase sequence changes (wiring error or missing phase), the red and green LEDs on the protector flash simultaneously (fast or slow depending on the fault), the protector disconnects, and the motor cannot start.

Recovery: Once the correct phase sequence is restored, the motor automatically reconnects.

Operating Status Indicator:

Normal Operation: When voltage is normal and phase sequence is correct, the green LED lights steadily, the protector operates normally, contacts 15 and 18 close, and the motor starts running.

Fault Indications:

• Red and green LEDs flash rapidly or both off: indicates phase loss fault.

• Red and green LEDs flash slowly simultaneously: indicates incorrect phase sequence (wiring order error).

• Red LED steady on (or green LED flashing): voltage difference between any two phases exceeds 50V.

Why Choose ONESTO MRVX7?

Comprehensive Protection without Blind Spots: Accurately detects three-phase voltage imbalance (trips automatically if difference exceeds 55V), phase loss, and incorrect phase sequence faults, preventing motor damage from the root cause, while also protecting motor rotation direction—covering core motor operation risks.

High-Precision Voltage Sampling: Voltage sampling accuracy up to ±1%, ensuring precise detection and quick response to voltage abnormalities for stable motor protection.

Intelligent Adaptation for Peace of Mind: With a 4-second power-off delay and 2-second recovery closure time, it effectively avoids false shutdowns caused by transient voltage dips; automatically reconnects when voltage difference recovers to within 50V, reducing maintenance costs.

Low Power Consumption and High Efficiency: Standby power consumption only 0.2W, operating power consumption 0.6W for energy saving in long-term use; maximum load current AC-1:8A, AC-15:3A, suitable for most industrial three-phase motors.

Application Scenarios:

Industrial Motor Protection

Used for three-phase motors driving large machinery on industrial production lines to prevent overheating and burnout caused by phase loss, incorrect phase sequence, or voltage imbalance.

Applied to cranes, conveyors, fans, and other equipment to ensure safe and stable operation.

Pumps and Compressor Systems

Protects pump and compressor motors from operating anomalies caused by phase loss or voltage differences, preventing equipment damage and downtime.

Suitable for water supply, drainage, and industrial cooling systems.

HVAC Systems

Ensures three-phase motors in air conditioning and refrigeration systems operate under normal voltage and correct phase sequence, avoiding electrical faults that cause system downtime or efficiency loss.

Agricultural Irrigation and Rural Motor Control

Protects motors in agricultural irrigation equipment, preventing damage caused by unstable rural power grids or wiring errors.

Elevator and Escalator Control Systems

Ensures correct phase sequence and balanced voltage for elevator and escalator drive motors, guaranteeing passenger safety and equipment stability.

ONESTO invites global distributors and wholesalers to join us in expanding the industrial automation and motor protection market. We offer you comprehensive motor protection solutions to enhance market share and brand influence.

For detailed information, please contact the ONESTO sales team to start a mutually beneficial partnership!