×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Wacky controls

Wacky controls

Wacky controls

(OP)
Ran across an interesting problem with a JC P66 speed control for a condenser fan motor. Fan motor is 230/1/60 on a 460/3/60 unit. Used step down transformer to get 230 volts.Control requires 24 volt power supply for transducer.
Used 24v of of units controls which was fed from a separate power supply. Wired everything and speed control would not work. Jumped across speed control and motor ran at full speed. Replaced P66 control and still didn't work correctly. Broke down and read instructions on P66 and it said 24v had to be on same phases as motor. Installed 230/24v transformer using L1 and L3 (same as 460/230v transformer) and everything worked. My question is why the 24v from separate feed did not operate control.

RE: Wacky controls

  The way I interpret what you said is the first supply from a separate source was a DC supply, but the second source you used was a 24 volt AC signal supplied by a step down transformer.
 
  Was the first supply an AC supply or DC supply?  

Even if the first supply was AC there could be issues. I don't know the specifics of the controller, but usually when you have to connect from the same supply it is because of a phasing issue.  Using the same supply means the controller knows the phasing of the supply.   A separate supply could be out of phase.

RE: Wacky controls

(OP)
Both supplies were 24vac.

RE: Wacky controls

  I tried a search for the JC P66 controller but found nothing.  I believe it is either a phasing issue or a common issue.  You would have to have a diagram of the circuit if you are going to try to figure this out.

  Phasing problems were common with old DC drives.  In first reading I assumed the controller was IGBT, since it is for AC but considering it is single phase it could be SCR or Triac based which would definitely bring up the phasing concern.

  To understand phasing remember your facility is getting three phases supplied to it ABC.  The controller may be wired to AB.   Your second supply may be AC or BC, thus the phasing would be off.  Note if it was connected BA, even that could be a problem. If they are specific in their instructions, that a certain power input is connected to a certain control input, (i.e. a wire to power input 1 must be connected to control input 1), then your circuit is sensitive to this type of phasing error.

RE: Wacky controls


It is possible that the 1ø controller used triac or SCR gating to vary the motor speed.  Gating of the triac relied on a combination of 24VAC control and 230V sine waves peaking and zero-crossing at the same moment.  With control voltage on another phase, the controller may not have been able to “keep up” with out-of-sync waveforms.  
  

RE: Wacky controls

If soild state controls they may have sensors like a car computers to see if every thing is running right -if not it will shut down.

RE: Wacky controls

Suggestion: The complete schematic diagram would be necessary to answer the question correctly.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources