Automatic star-delta switch / star-delta time relay

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

The ERV-YU starting relay is designed for automatic control of electric motor starting in STAR-TRIANGLE mode at an operating voltage of 24/220 V AC. The relay ensures smooth motor starting, reduces starting current, and extends the overall lifespan of the drives. It is equipped with ON-, STAR-, TRIANGLE mode indicator lights 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 flow. When the required speed is reached, the winding automatically switches to TRIANGLE mode, in which the motor continues normal operation.

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

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

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

• When time t1 elapses, the STAR contact is interrupted, the indicator light goes off, and a short pause t2 (15 ms) starts.

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

Usage

The ERV-YU relay is suitable for:

• automatic motor switching control in star-delta mode

• industrial applications where high requirements for stable and safe motor starting exist

• systems where reducing starting current and protecting the electrical network are necessary

Additional options

For the relay, you can purchase:

• contactors and starters

• contactors with mechanical interlock

• separate mechanical interlock modules

• metal enclosures with IP65 protection rating

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