Automatic star-delta switch / star-delta time relay

Relays for Star-Delta Trigger Modes (ERV-YU)

The ERV-YU starting relay is designed for automatic starting control of electric motors in STAR-DELTA mode at an operating voltage of 24/220 V AC. The relay provides smooth motor start-up, reduces starting current, and extends the lifespan of the entire drive system. It is equipped with light indicators for ON, STAR, and DELTA modes and allows setting the start time.

Description and operating principle

To ensure a smooth start of the electric motor, the STAR mode is activated first, which reduces the initial current surge. Once the desired speed is reached, the winding automatically switches to DELTA mode, where the motor continues to operate normally.

Automatic mode switching with relays and contactors increases the stability of the entire system and eliminates risks associated with manual operation.

When voltage is applied to the A1-A2 terminals of the relay:

• the STAR contact is activated, the STAR indicator lights up, and the start interval t1 (0.1-30 s) begins to count.

• After time t1 has elapsed, the STAR contact is disconnected, the indicator goes out, and a short pause t2 (15 ms) begins.

• Then the PHASE-DELTA contacts are switched on, the DELTA indicator lights up, and the relay remains in this mode as long as voltage is supplied to the A1-A2 terminals.

Application

The ERV-YU relay is suitable for:

• automatic motor switching control in star-delta mode

• industrial applications with high requirements for stable and reliable motor starting.

• systems where it is necessary to reduce the starting current and protect the electrical network.

Additional range

For this relay, you can purchase:

• contactors and starters

• contactors with mechanical interlock

• separate mechanical interlock modules

• metal enclosures with IP65 protection

All this is available directly from stock at competitive prices.