How to Control a 3-Phase Motor from Multiple Places?

Electrical Technology

Controlling the ON/OFF Operation of a 3-Phase Motor from Multiple Places

Controlling a motor from different places is necessary in various scenarios, primarily driven by the need for operational efficiency, safety, and convenience. We may use various approaches to control a three-phase motor from multiple remote locations, including conventional methods such as pushbuttons, as well as advanced technologies like PLCs, HMIs, and wireless control. This is particularly applicable in large commercial and industrial premises. In the following article, we will show how to control the ON/OFF operation of a three-phase motor using DOL starter and push-buttons with the help of power and control circuit diagrams.

Related Post: How to Start & Stop a 3-Phase Motor from Multiple Locations?

Components Needed

Three-Phase Motor
DOL Starter (Based on Contactor & O/L Relay)
2P-MCB and 3-P MCCB
3 or More Nos. of NO/NC Switches
Single Phase & Three Phase Supply
Wires & Cables

Power and Control Diagrams

The following wiring diagrams show the controlling of a 3-Phase motor from different places using DOL starter and pushbuttons.

Power Diagram

Control Circuit Diagram

Challenges of Multi-Button Motor Control

Controlling a 3-phase motor from more than two buttons introduces several challenges:

Interlocking: To prevent conflicting commands from multiple buttons, an interlocking mechanism must be in place. This ensures that only one command (start or stop) is executed at a time. This prevent the damage to the motor or machinery.
Complexity: As the number of control buttons increases, so does the complexity of the control system. Design and wiring can become intricate.
Distance: The control stations may be located far apart, making it impractical to run wires directly from each station to the motor starter.
Safety: Emergency stop functionality must be available at all control points to ensure the safety of personnel and equipment.
Reliability: The control system must be reliable, ensuring that a command to start or stop the motor is always executed correctly.

Working of the Motor Control Circuit

Let’s see how the control circuit of a 3-phase motor can be operated from more than two locations using pushbuttons.

Multi-Button Control Stations

One straightforward approach is to install multi-button control stations at various locations within the facility. These stations are wired directly to the motor starter’s control circuit. Each station can include multiple buttons for different functions, such as start, stop, forward, reverse, and speed control.

In the above circuit, three ON (NO) and OFF (NC) pushbuttons are used. (Additional ON/OFF buttons may be added if you want to control the motor from even more places. An additional emergency stop buttons may be added for extra protection.)

As shown, when the operator presses the ON 1 switch, the holding circuit is completed since all the OFF pushbuttons are normally closed (NC). Consequently, the contactor energizes, and the motor starts running.

When the operator presses the OFF 1 switch, the entire circuit is interrupted because all the ON buttons are normally open (NO). Thus, the holding circuit releases its contacts, and the motor stops.

This same process applies to all pushbuttons, whether they are ON or OFF.

Advantages: