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ON / OFF 3-Phase Motor Using 14-PIN Relay and DOL Starter

How to Start and Stop a Three-Phase Motor using 14-PIN PLA Relay and DOL Starter?

Controlling a 3-phase motor using a DOL starter is the simplest method among others, such as star-delta starters, VFD starters, relay starters, and PLC-based starters, etc. In the following motor control guide, we will discuss how to control the ON and OFF operation of a three-phase motor using a 14-PIN relay and DOL starter, along with wiring, power, and control circuit diagrams.

A A (DOL) Direct-On-Line starter is a simple motor starter consisting of a contactor and overload relay. we have used 14-terminal PLA relay to control the DOL starter and motor. A 14-PIN relay is an electromechanical device designed to control complex functions within a circuit. In this setup, the 14-PIN relay serves as the interface between the control circuit and the DOL starter, enabling remote or automated control over the motor’s operation.

Components Needed

To make a simple ON and OFF control circuit for a 3-phase motor using a 14-PIN relay and a DOL starter, the following components are required:

  1. Three-Phase Motor
  2. 14-PIN PLA Relay
  3. DOL Starter (based on Contactor & Thermal Overload Relay)
  4. 2P-MCB and 3-P MCCB
  5. Control Switches (Start “NO” and Stop “NC”)
  6. 3 NO of polit light indictors
  7. Single Phase & Three Phase Supply
  8. Wires & Cables

Wiring the Power and Control Circuit

According to the following wiring, power and control diagram, follow the given basic steps to wire the circuit for controlling the ON/OFF operation of a three-phase motor using an 14-PIN relay and a DOL starter.

ON-OFF 3-Phase Motor Using 14-PIN Relay & DOL Starter

    1. Connect the three-phase power supply of 415V AC from the 3-P MCCB to the L1, L2, and L3 terminals of the Contactor, O/L relay (T1, T2, T3) , and then the 3-Phase motor (U1, V1 & W1) respectively (wiring power circuit).
    2. Connect the Phase (Line) wire from 2P-MCB to the 95-NC terminal of the O/L relay
    3. Connect two push-buttons in series (RED-NC to Stop and Green-NO to Start) from the 96-NC terminal of the O/L relay. Now, connect the output terminal of the NO-push-button (Green) to the 12-COM and 13-L terminals of the 14-PIN relay (as shown in control diagram).
    4. Connect a jumper wire for holding from the output of the Red-NC (Stop) push button (or the starting point of the Green-NO push-button) to the 8-NO terminal of the PLA relay.
    5. Wire the 5-NO terminal of the PLA relay to the 1st (starting) terminal of Red (NC) pushbutton.
    6. Now, wire the A1 terminal of contactor to the 9-COM terminal of 14-Pins Relay.
    7. Connect the neutral wire from the MCB to the A2 terminal of the contactor and 14 terminal of the 14-PIN relay.
    8. Finally, properly ground the motor, DOL starter, and control circuit to ensure safety.

Working of Starting & Stopping 3-Phase Motor using 14-PIN Relay & Contactor

  1. Pressing the start button energizes the relay’s coil, which activates the DOL starter’s contactor.
  2. This is because, the NC becomes NO and vice versa. But the holding wire (to 8-NO & 5-NO) makes sure continuous latching circuit i.e. removing the pressure from Green (Starting) pushbutton won’t disconnect the circuit from power supply.
  3. When the PLA relay activates, its 8-NO becomes 8-NC with 12-COM and 2-L. Similarly, 5-NO becomes 5-NC with 9-COM which complete the circuit and activate the contactor connected to the O/L relay and 3-Phase motor. If you remove the finger from Green (starting – NC) pushbutton, the circuit will still running because, power supply is still connected to the 12-COM and 13-L via holding wire from 8-NO.
  4. The DOL starter connects the motor windings directly to the three-phase power supply, initiating the motor’s start-up sequence.
  5. The motor accelerates to its rated speed.
  6. Pressing the stop button de-energizes the relay’s coil and holdover the holding circuit to the initial state, deactivating the DOL starter. The motor comes to a stop.

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