Automatic star-triple switch / star-triple time relay

Star-Delta Starting Mode Relays (ERV-YU)

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

Description and Operating Principle

For smooth starting of the electric motor, the STAR mode is first activated, which reduces the initial current surge. Once the required speed is reached, the winding automatically switches to DELTA mode, in which the motor continues normal operation.

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

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

• The STAR contact activates, the STAR indicator lights up, and the starting interval t1 (0.1-30 s) begins counting.

• After the time t1 elapses, the STAR contact opens, the light turns off, and a short pause t2 (15 ms) begins.

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

Applications

The ERV-YU relay is suitable for:

• automatic control of motor switching in star-delta mode

• industrial applications requiring stable and safe motor starting

• systems where starting current needs to be reduced and the electrical network protected

Complementary Program

For the relay, you can purchase:

• contactors and starters

• contactors with mechanical interlocking

• standalone modules with mechanical lock

• metal enclosures with IP65 protection

All of this is available directly in stock at competitive prices.