Polyphase Induction Motors

Figure 1: A typical three phase motor.

                                                     

Electrical Wiring Diagram Star Delta Control and Power Circuit Using Mitsubishi PLC Program

This article is intended to diagrammatically demonstrate the concept of the wiring principle of a star delta (wye delta) motor control and power circuit when using a PLC (Programmable Logic Controller) ladder program to control the switching of a 440 volts induction motor.

Why does a 3 phase AC induction motor have to be connected in star delta (or wye delta) configuration - What is the significance and advantage of using star and delta in motor connection

Three phase AC induction motors are known to have a very high start-up surge current. The most practical approach to reduce the high start-up inrush current is by firstly implementing a star (or wye) configuration to the motor's 6 leads wiring terminal during the start-up run of the motor. When the motor slowly picks up speed and a significant decrease in the amount of current is achieved then the motor's 6 leads wiring terminal is then reconfigured to a delta connection.

Flowchart schematic diagram for the Control Circuit of a Forward Reverse Star Delta or Wye Delta Electric Motor Controller - A how to learn skills training guide for electric motor controller

To help facilitate for a better understanding and further learning and training on the concept of the forward reverse star delta (or wye delta) control (ckt) circuit covered in our previous article, a reversible star delta starter control circuit diagram accompanied with a flowchart diagram is presented below as a follow up learning guide which shows a schematic representation of the sequence of operation for the starting and stopping and running operation of a reversible star delta or wye delta electric motor control circuit in order to provide a visual aid to help diagrammatically visualize how the control circuit flows.

Flowchart schematic diagram for the Control Circuit of a Star Delta or Wye Delta Electric Motor Controller - A how to learn skills training guide for electric motor controller

To help facilitate for a better understanding and further learning and training of the concept of the star delta or wye delta control (ckt) circuit covered in our previous article, a flowchart diagram is presented below as a follow up learning guide which shows a schematic representation of the sequence of operation for the starting and stopping and running operation of the star delta or wye delta electric motor control circuit in order to provide a visual aid to help diagrammatically visualize how the control circuit flows.

Control Circuit of a Star Delta or Wye Delta Forward Reverse Electric Motor Controller - A basic industrial process automation control how to do guide for reversible star (wye) delta motor controller

An electrical schematic diagram for the power circuit of a reversible star delta or wye delta motor controller was tackled in our previous article, where it showed an illustration of the wiring combinations using three (3) phase circuit breakers, magnetic contactors and thermal overload relay to achieve the different variation of motor terminal connections in star and delta configuration in relation to the three (3) phase supply source voltage, hence the term power circuit diagram.

Power Circuit of a Star Delta or Wye Delta Forward Reverse Electric Motor Controller - A basic industrial process automation control how to do guide for reversible star (wye) delta motor controller

Our previous article covered a typical star delta or wye delta motor controller which is focused on a common circuit intended for a single rotational direction of a 3 phase AC induction motor. But certain star delta motor control applications would also require a reversible motor rotation.

Star Delta or Wye Delta Industrial Process Automation Control Motor Wiring Configuration - Recommended wiring configuration suitable for reduced changeover current peaks from star to delta motor connection - A basic How To Learn Guide

Fig-1

With reference to our previous articles which covered the star delta or wye delta motor wiring configuration - the delta motor wiring diagram presented in Fig-1 on the right shows two of each of the six motor terminals joined together and while connected also to each of the three reference source voltages that conforms to an orderly configuration of phase sequence U1-V2-L1, V1-W2-L2, W1-U2-L3.

Control Circuit of a Star Delta or Wye Delta Electric Motor Controller - A basic how to guide

Controlling the interchanging star connection and delta connection of an AC induction motor is achieved by means of a star delta or wye delta control circuit. The control circuit consists of push button switches, auxiliary contacts and a timer to act on the conditional contact point logic and time duration which upon reaching a specified time period would provide the switching sequence of the magnetic contactors configured specifically for a star connection and a delta connection of the motor terminals.

The control circuit discussed here consists of conventional physically hard-wired electrical components, wherein each components are individually wired using electrical cables fastened with screws to wiring terminals located in the electrical components. The introduction of logic controllers, however, has made it possible for such tedious wiring task to be conveniently constructed by drawing graphical representations of the circuit on a computer terminal to assemble the sequential logic of the circuit programmed by using a computer software, which is covered in the article Star Delta Control Circuit Using Programmable Logic Controller.

Star Delta or Wye Delta Motor Wiring Configuration - A basic how to guide

The previous article which covered the star delta motor control power circuit for industrial process control presented an electrical diagram showing the interchanging motor wiring configuration for a star connection and a delta connection using magnetic contactors as motor starters. Exploring further with reference to the previous star delta power circuit diagram, if you manually trace each line connections going to the motor you will begin to understand how the following star and delta motor wiring connections are achieved.

Power Circuit of a Star Delta or Wye Delta Electric Motor Controller - A basic how to guide

Reduction of the AC induction motor's starting inrush current is achieved by implementing an interchanging star delta or a wye delta connection of the motor, this can be done by incorporating a configured star delta connection of the motor by using magnetic contactors or magnetic starter switches. The diagram below illustrates this type of motor switching connection used in every electrical industry involving industrial process automation control technology.