Relay accessories devices

Electronic Timer for Star-Delta Starters


When used in star-delta starters, the Electronic Timer lags the star connection and provides a lapse of 50 ms before
the switch over to delta connection.


According to the type of device chosen, the electronic circuit has a 24 V a.c./d.c., 110 to 120 V a.c., 220 to 240 V a.c. or 380 to 440 V a.c. supply.

An output relay with reversing contact ensures high current switching. A two-position switch allows selection of one of the two time delay ranges: 0.8 to 8 s or 6 to 60 s. The 0.1 to 1.0 graduated button allows an initial setting without steps within the previously selected range which can then be adjusted using a chronometer.


On energization, the green U indicator light (voltage applied) comes on. Contact 15-16 then immediately moves to the closed position. Count-down of the programmed time immediately commences. When the time delay has elapsed, contact 15-16 opens and at the same time the 50 ms lapse, t2, begins after which contact 15-18 moves to the closed position.

The yellow R indicator light comes on. On de-energization, the U and R indicator lights go out and, after the 250 ms resetting time, the device is ready
for a new cycle.

Image – TE5S Electronic Timer for Star-Delta Starters

Electronic Timer for Star-Delta Starters Equivalent diagram - Electronic Timer for Star-Delta Starters Front face - Electronic Timer for Star-Delta Starters

Mechanical and Electrical Interlock Units

When mounted between two contactors, the mechanical interlock unit prevents one of the contactors from
closing as long as the other contactor is closed.

VM… interlock units for mechanical interlocking of two horizontal or vertical mounted a.c. or d.c. operated contactors.
VE… interlock units for mechanical and electrical interlocking of two horizontal mounted a.c. or d.c. operated contactors.
relay mechanical interlock

relay electrical interlock unit

terminal marking and position - mechanical , electrical interlock unit

Mechanical Latching Unit

For converting standard contactors into latched contactors.
heWB 75-A block contains a mechanical latching device with electromagnetic impulse unlatching (a.c. or d.c.)
or manual unlatching.

After closing, the contactor continues to be held in the closed position by the latching mechanism should the
supply voltage fail at the contactor coil terminals.
Contactor opening can be controlled:
– electrically by an impulse* (a.c. or d.c.) on the WB 75-A block coil.
* the coil is not designed to be permanently energized.
– manually by pressing the pushbutton on the front face of the WB 75-A block.

Mechanical Latching Unit of relay
Mechanical Latching Unit of relay

Relay Blocks

  • Impulse contact blocks- N.O. contact with a black pushbutton (“ON” function), N.C. contact with a red pushbutton (“OFF” function).
  • Lamp holder blocks – Lamp holder for indicator light.
  • Fuse holder blocks- Fuse holder for the control circuit.
relay blocks - Impulse contact blocks, Lamp holder blocks, Fuse holder blocks
relay blocks – Impulse contact blocks, Lamp holder blocks, Fuse holder blocks

Interface of Relay

Interface relay is designed to receive 24 V d.c. signals delivered by PLC’s or other sources with a low
output power and to restore them with sufficient power to operate the coils of the relevant A 9 … A 75
contactors or the N… contactors relays.

Example – RA5 interface relay of ABB.

Interface relay
Interface of relay

interface relay with relay

RA 5 interface relay is made up of a miniature electromechanical relay equipped with a N.O. contact and with a low consumption 24 V d.c. coil. The interface relay coil is controlled by the PLC while the N.O. contact ensures switching of the power contactor.

The “E1+” and “E2–” input terminals must be connected, according to their polarity, to the PLC output.
The RA 5 is equipped with two terminal pads for connection to the A1 and A2 terminals of the contactor coil.
This coil is supplied between the A0 and A2 terminals of the RA 5.

interface relay circuit diagram
Interface relay circuit diagram

Relay terminal Blocks

Additional terminal block is designed to increase the connecting capacity of the contactor on which it is fitted and for preparation of the wiring before final connection on the contactor.

relay terminal block
relay terminal block

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