PLC with motors.

[subbarayan]

Iam an instrumentation engineer working in industrial automation softwares as well as real time embedded systems.I would like to know how can a PLC(PROGRAMMABLE LOGIC CONTROLLER)be interfaced with a single/3 phase motor
so that I would be able to do speed control by my PLC.I would like to know both the physical Input and Output connections.

 

[way]

You need to purchase and install a speed or frequency controller to control the speed of the motor. A frequency controller (also called Variable Frequency Drive) allows the user or a PLC to choose the frequency that the motor operates at.

Once you have the speed controller installed on the motor, then you will need an 4-20 MA or 0-5 V output from the PLC to the controller. The controller will then adjust the frequency of the motor based on the signal from the PLC. As far as inputs into the PLC, you will need some feedback (i.e. level, flow, etc.) that you will use to control the speed of the pump. Then you can set up a control loop to run the entire system in auto.

Note: In some cases, there may be less expensive alternatives. For example, if the motor is controlling a pump, it may be cheaper to install a control valve on the discharge piping rather than purchase a speed controller for the pump.

 

[plc123]

Hi,
some Variable Speed Drives ( Siemens Micro- Midi-Master) have 4 types of control:
1. Analog configurable input (I,V)- then you need PLC with analog I/O,
2. Discrete Inputs ,
3. Network Input,
4. Keypad control

Thanks, Vladimir

 

[adil4adil]

hi sdubbarayan

PLC are given basdic input & output either we can take feedsback from the motor by encoder and have close loop control or we can give direct output to the motor in descrete output to
inverter so that we can have n nos of motor speed at different steps
good day