×
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

Winding Resistance Fractional HP Motor

Winding Resistance Fractional HP Motor

Winding Resistance Fractional HP Motor

(OP)
We had an issue back tracing some wires through a terminal strip.  There are 4 - single phase 110Vac 2 pole motors, each hot wire connected to an individual terminal.
Neutral/Common are all connected on a busbar.

What occurred when i did some continuity tests with a multimeter, was if i put 1 lead on the hot wire of 1 motor, i would get continuity through the other 3 hot wires BUT not through the neutrals.

Kind of thrown off by this.
I thought that with a continuity test, if the resistance is too high (which through windings of a motor lead me to believe that) i shouldnt be able to have continuity through all 4 motors.

Any ideas?

Paul

RE: Winding Resistance Fractional HP Motor

I can't quite follow you. Is it the fact that you have continuity through the motors that disturb you? Most windings are quite low ohm. So you should have continuity.

Or is it the fact that you don't have continuity from winding to neutral that you find confusing? That is also perfectly normal - there is no connection to neutral in a three-phase motor.

Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

RE: Winding Resistance Fractional HP Motor

PNA

Please clarify.
4 single phase motors. Two terminal leads per motor?
Connected to different phases of a 3-phase system?
I assume the motors are off line when the continuity test is performed, is it? but one terminal (to neutral) is still tied to the other 3 common leads?

RE: Winding Resistance Fractional HP Motor

(OP)
Thanks for the responses

This is a 110 Vac single phase 60 hertz Canadian.
1 hot wire (black) 1 neutral wire (white) and 1 ground wire (green).

(For the UK and Europe, it would be 220/230/240 single phase) which is 1 hot wire (brown), 1 common (baby blue), 1 ground or pe (green with yellow)

We have the motors each on there own switch.
All switches are off.

There is no power applied to any motors.

Yes 1 terminal is tied to the other 3 common leads.

Paul

RE: Winding Resistance Fractional HP Motor

I believe that the signal path the ohm meter is "looking" is:  Thru the motor whose hot lead you have one meter lead on, which has continuity to the neutrals (whether tied together there, or earlier in the control or ultimately, the electrical service panel) have continuity to all three motors thru their windings.  If the motors each have a DC resistance, for instance, 100 ohms, then you should be seeing 200 ohm readings from any motor hot to any motor hot.

BK

RE: Winding Resistance Fractional HP Motor

Try to measure continuity from one spot on the neutral busbar to another spot on aathe neutral busbar. If you still don't get continuity, clean the surface of the busbar and try again.
respectfully

RE: Winding Resistance Fractional HP Motor

Yes, I too think the problem here is in your not measuring continuity to the neutral(s). You should, AND that would coincide with your being able to measure through to the other hots. Probably a measurement error, i.e. bad connection as waross implied.

JRaef.com
"Engineers like to solve problems.  If there are no problems handily available, they will create their own problems."   Scott Adams  
For the best use of Eng-Tips, please click here -> FAQ731-376

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