How to Start and Stop a Three-Phase Motor using 11-PIN PLA Relay and DOL Starter?
There are various methods for controlling, starting, and stopping three-phase motors, such as Star-Delta Starter, DOL starter, PLC, and VFD-based methods etc. In today’s tutorial, we will demonstrate how to start and stop a 3-phase motor using an 11-PIN relay and a DOL Starter (based on a contactor and thermal overload relay) with the help of wiring, power and control circuit diagrams.
A Direct-On-Line (DOL) starter (consists of a contactor, thermal overload relay) is a widely used method to start and stop three-phase motors while an 11-PIN relay is an electromechanical switch designed to control various functions within a circuit.
To create an ON/OFF control circuit for a three-phase motor using an 11-PIN relay and a DOL starter, the following components are needed:
- Three-Phase Motor
- 11-PIN PLA Relay
- DOL Starter (based on Contactor & Thermal Overload Relay)
- 2-MCB and 3-P MCCB
- Control Switches (Start “NO” and Stop “NC”)
- 3 NO of polit light indictors
- Single Phase & Three Phase Supply
- Wires & Cables
Wiring the Power and Control Circuit
Follow these steps to properly wire the circuit for controlling the ON/OFF operation of a three-phase motor using an 11-PIN relay and a DOL starter as shown in the following wiring, power and control diagram.
- Connect the three-phase supply of 415VAC via a 3-P MCCB to the 1L1, 3L2, and 5L3 terminals of the Contactor, O/L relay (2T1, 4T2, 6T3) , and then the 3-Phase motor (U1, V1 & W1) respectively (wiring DOL Starter).
- Connect the phase (line) wire from 2P-MCB to the 95-NC and 98-NO terminals of the overload relay
- Connect two pushbuttons in series (RED-NC to Stop and Green-NO to Start) from the 96-NC terminal of the overload relay. Then, connect the output terminal of the NO-pushbutton to the 1st terminal of Red pilot light indictor, A1 terminal of contactor and 2 (Line) and 3-NO terminals of the 11-PIN relay respectively as shown in fig.
- Wire a jumper from the output of the Red-NC (Stop) push button (or the starting point of the Green-NO switch) to the 6-NC and 5-COM terminals of the PLA relay.
- Connect the 1-COM terminal of the PLA relay to the 1st terminal of Green pilot light indictor.
- Now, wire the 1st terminal of Yellow/Orange pilot light indictor to the 97-NO terminal of O/L Relay.
- Finally, connect the neutral wire from the MCB to the A2 terminal of the contactor, 2nd terminals of all three indicators and the 10 terminal of the 11-PIN relay.
- Finally, properly ground the motor, DOL starter, and control circuit to ensure safety.
Working of Starting & Stopping 3-Phase Motor using 11-PIN Relay & Contactor
- When the Motor is not running, the Green Indicator (connected through 11COM and direct 8NC) is glowing which indicates the motor is stop.
- Pressing the start button energizes the relay’s coil, which activates the DOL starter’s contactor.
- This way, the NC becomes NO and vice versa. But the holding wire (to 3-NO & 8-NC) makes sure continuous latching circuit i.e. removing the pressure from Green (Starting) pushbutton won’t stop the circuit.
- When the 11-Pin relay activates, its 3-NO becomes 3-NC with 1COM and 2-L which complete the circuit and activate the contactor connected to the O/L relay and 3-Phase motor.
- The DOL starter connects the motor windings directly to the three-phase power supply, initiating the motor’s start-up sequence. Hence, the Red Indicator ON which indicates the motor is running.
- The motor accelerates to its rated speed.
- Pressing the stop button de-energizes the relay’s coil and holdover the holding circuit to the initial state, deactivating the motor’s starter. The motor comes to a stop.
- The yellow/orange indicator only glows when the circuit trips due to overloading.
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