3-Phase motor control using a PLC

[Lancie1]

Shohadawy,

What they are trying to say:

1. Normally, a 3-phase industrial motor is NOT connected directly to a PLC. If you want to control the speed of a 3-phase motor using a PLC, you must have some additional equipment, such as a Variable Speed Motor Drive.

2. You may have an instructor that has some type of small toy motor that can be connected in some fashion to a PLC, but this is not very useful in the real world. If that is the case, you should know that it is only for experimenting and has no useful function except for learning about PLCs.

 

[MASEngr]

Note that if you're connecting a toy motor to a PLC, the transient voltage can be enough to damage your PLC.

If you're running a 24V system and turn off your motor, you could easily be looking at 200+ V across the output. You may not notice until you get premature failures.

Treat every connection as a long-term connection, and make sure that you put in the proper transient suppression systems.

 

[TConnolly]

OK, I think we've had enough fun with this.

Basic IEC wiring diagram for a three phase motor starter with PLC and start/stop buttons. The PLC does not wire to the motor, it operates K1M, which switches line voltage to the motor.

 

[bkottaras]

Are we feeling a bit guilty this late at night??
Personally, I enjoyed the thread!
And will apply the rotating PLC setup soon I hope!

 

[Protiusmime]

Well, it's early morn for me. And yet, this charade has given me some energy to make it till the end of shift. I can't draw very well nor quickly in Visio. But I do envision waving a PLC quickly up and down in front of and perpendicular to a motor stator. I'm actually beginning to feel some torque. This moves me

Now for the more serious side... while we all have been chuckling, this feller has probably gone about inventing exactly the PLC techno that can spin up a 3p 50h mover... and chuckle right along with us, on his way to the bank