ECN Forum Forums Technical Discussion Electrical Theory and Applications Discussion for: Forward / Reverse motor control

Discussion thread for: Forward Reverse AC Motor Control

Feel free to make comments here!!!

Scott SET

P.S. Forgot to complete the subject on the first one ... sorry

SET

F & R should have an interlock right???

Scott,
Are people still installing 480 volt control circuits? I haven't seen one installed since I started in trade in '73. I have worked on a few that were installed before I started.
Don(resqcapt19)

well a lot of times there is just no noodle...

Some self-contained starters with cover mounted controls forego the control transformer. I wouldn't run a 480 control ckt. outside the confines af the starter enclosure.

sparky,
Do you mean a mechanical interlock? Don't the NC contacts provide electrical interlock?

The NC contacts prevent the forward and reverse coils from being energized simultaneously. They don't, however, prevent someone from pressing reverse (or forward) before the motor has stopped turning.

Some starters have a mechanical interlock, most don't. Are we actually talking about an anti-plug circuit to prevent rapid reversal of the motor. Some high speed or heavy loads such as punch presses do use them.

As far as I know all NRTL listed reversing starters come with a mechanical interlock between the F and R contactors. Electrically interlocking the coils is not suffcient to prevent against the creation of a bolted fault.

Scott, the normal convention is to show the contacts of each device next to each other. All of the F power contacts should grouped together rather then intermixed with the R contacs.

Hi all, thanks for the comments!!!

I drew these schematics as basic as possible, to keep them as simple as possible.

Only reasons for the 460 VAC input and control circuit were to keep the motor's windings proper [notice how they are series connected, rather than parallel?], and also to show simple control circuitry.

Believe me, I would use a control transformer here!!! Next set of schematics will be more detailed and will include control transformers where applicable.

JBD:Ya, I should have drawn the motor contacts in order - just thought this way would make it easier for people not familiar to motor control circuits. I figured this would better show how the reversal of the Lines is accomplished. Thank you for the heads up! Future drawings will be done more pro!

This schematic shows a crude and basic interlocking control circuit with N.C. contacts for the interlocks in the control circuits for F and R.

This schematic is by no means the best method for this control. It's just to show basics.
Glad that you all made comments about this so others would not begin applying these simple setups to real world applications!!!
I need to remember that when posting schematics on-line, and make note of these facts when posting basic stuff.

Once again, thanks for the comments!!! Hope to have more drawings posted this weekend.

Scott SET