How would I go about connecting a 3 phase motor (230V – 2.5A) to a MicroLogix 1500 PLC? What components would I need? As soon as the power of application is turned on, I would like the motor to be turned on and when it is off, I would like motor to be turned off. Can I just use a IEC contactor? I know how to program in the PLC but having trouble on how its all connected? Please help...

Edward

 

First, you need to list all of I/O devices to be controlled by Micrologix 1500, which can be divided into 4 categories:
- Digital Input (DI)
- Digital Output (DO)
- Analog Input (AI)
- Analog Output (AO)

Within this posting you just mentioned one device: 3 phase 230 VAC motor I/O device which can be considered as Digital output device.

Next step, connect the 3 phase motor to Micrologix 1500 relay contact type Digital output channel. Of course you need motor contactor so Micrologix can
drive the 3 phase AC motor by energizing the contactor coil.

Because the Micrologix DO relay contact capability is low and the contactor coil is inductive load, you will need an interposing relay to be connected to the Micrologix 1500 DO channel. Micrologix DO will energize interposing relay coil, and interposing relay will energize motor contactor coil.

 

What is it you wish to accomplish with the Micrologix? Why not use a properly rated contactor with start/stop buttons? If you want to control the contactor with the PLC, make sure the contactor's coil is not gonna draw too much for the PLC's rated outputs (if so, you may have to use a relay) if you do use the PLC's I/O to control the contactor (to start and stop the motor) then make sure the start/stop circuit also goes through the PLC. Don't forget estops! Remember with the relative control one gets from a frequency drive, and ease of I/O configurastion these days, maybe a drive should be considered especially if you want speed control and close over current protection and braking.

Best Regards,

Mark

 

The motor is a filtermist unit, and right now it's just being controlled by an on and off switch, but they want the unit to be on only when the machine is and off when the machine is off, due to operators turning it off and forgeting to turn it back on.