Star-Triangle Automatic Switch / Star-Triangle Time Relay

Relay for star-delta starting modes (ERV-YU)

The ERV-YU starting relay is designed for automatic control of electric motor starting in STAR-TRINAGON mode at an operating voltage of 24/220 V AC. The relay ensures smooth motor starting, reduces starting current, and extends the service life of the entire drive system. It is equipped with indicator lights for the ON, STAR, and TRIANGLE modes and allows the starting time to be set.

Description and operating principle

For smooth electric motor starting, STAR mode is activated first, reducing the initial current surge. When the required speed is reached, the winding is automatically switched to TRIPLE mode, in which the motor continues normal operation.

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

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

• The STAR contact is activated, the STAR indicator lights up, and the starting interval t1 (0.1–30 s) begins counting down.

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

• Afterward, the PHASE-TRIANGLE contacts are connected, the TRIANGLE indicator lights up, and the relay remains in this mode for 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 reliable motor starting

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

Complementary range

For the relay, you can purchase:

• contactors and starters

• contactors with mechanical interlocking

• standalone mechanical interlocking modules

• metal enclosures with IP65 protection

All of these are available directly from stock at competitive prices.