1. Home
  2. ⏚ Electrical Engineering
  3. measure single phase 240v motor

measure single phase 240v motor

a motor has been tripping out the breaker. (single phase 240v)
If i disconnect the motor from the contactor the breaker stays latched
the contactors also latch in indicating a fault on the motor.
How can I be sure that the motor is faulty?.
the motor has a capacitor on the top so i assume it's a capacitor
start/run motor.
The only wires going from the contactors to the motor are LIVE, NEUTRAL,
EARTH
If i put a meter across the live and neutral I get 2000 ohms which
sounds very high to me.
There dosen't seem to be any leakage from the live or neutral down to earth.
am i reading this right?
Reply to
Ronbol
Loading thread data ...
Not as I understand your post. 240v is 2 hots, not as you described "LIVE, NEUTRAL, EARTH" A neutral or grounded conductor would have no business in a 240v motor, not any I have seen.
Guessing your wiring is wrong inside the motor.
I do not have a clue why you would ohm the hot and neutral in this situation.
Reply to
SQLit
It might help if you post the name of the country you are in - otherwise you might confuse a few people.
The type of earth bonding your supply has may help too..
Reply to
Palindr☻me
If there where two hots and earth where would you ohmm?
Reply to
Ronbol
I assume you are measuring the resistance at the motor terminals with the power off, right? 1. Was the motor working before? 2. Does the motor try to start or it just sits there humming a few seconds before the breaker trips? 3. Have you tried to wire the motor to an other breaker? Observed any difference? If the answer is yes to 3., then I would check the starting capacitor and the centrifugal switch in the motor if there is one. Gene
Reply to
EpsilonRho
yes
has been yes
breaker trips straight away
breaker and motor contactor hold in without motor connected.
Reply to
Ronbol
UK supply, not sure on the earth bonding
Reply to
Ronbol
Before you begin to do anything with the motor, make sure that the breaker is not at fault. Replace the breaker temporarily with an other one with the same amperage. If it happens again, then the motor is the culprit. Testing the breaker without load is quite meaningless.
If it is the motor then we must exclude miswiring because you said it worked before. So what could it be?: 1. Motor mechanically frozen. Does the shaft rotate freely? 2. Any shorts inside the motor contactor? 2. Starting capacitor shorted ---> Replace and test 3. Winding shorted ----> buy a new motor or have it rewound if it is worth it.
Gene
Reply to
EpsilonRho
In England a single phase 240v motor would not work without a neutral.
So Its probably wired correctly.
The reason you would ohm the Live & Neutral would be to see if there was a short on the motor.
sQuick..
Reply to
sQuick
What are you using to measure the resistance?
If its just a normal multimeter a fault might not show up.
Really needs to be tested with an Insulation Resistance Tester.
sQuick..
Reply to
sQuick
OK so, between live and neutral still sounds high, does it to you.
Reply to
Ronbol
I agree. You should be using a Megger. What is the FLA of the motor, and what is your breaker size?
Reply to
engineer

Further Reading

  • Single phase motor

  • Hi again.Well I'm looking at a Denford Viceroy Centre Lathe. TDS1, but it...

  • 240v Single Phase GFCI - Wiring Issue

  • Ok - I'll start off by saying I am NOT an electrician - and No, I amNOT...

  • Bridgeport 3 phase to single phase

  • I'm be surprised if you couldn't find a used 3 phase motor and...

  • Stepping up 208V 3-phase to 240V 3-phase ?

  • I have 208V wye 3-phase in my shop. From the recommendation of this group,I...

  • Three Phase/Single Phase Voltage Fluctuations

  • Hi everyone.I hope this is the right group for this post of mine - hoping...

  • Re: Single phase 240v Motor in reverse

  • -If it is "capacitor start" then there will be a centrifugal switch as well...

  • Boxford STS lathe conversion to single phase

  • You've found that you have a dual voltage motor which is good but won't ...

  • Single phase motor problem

  • I have an old single phase 110V 5.6amp 1/3HP 1200rpm induction motorthat...

  • Single phase motor controller.

  • I know this is a very rudimentary question, but here goes anyway.I've got...

  • single-phase alpha-beta / dq transformation

  • Hello everyone.I am currently working on a single phase converter and need a to...

  • 240v 3 phase in 415v 3 phase motor

  • This almost certainly been asked before - Can I run 240v 3 Phase in 415 3phase...

  • 3-phase motor on single phase supply

  • I want to use a 3-phase 400V AC motor an a 230V single phase supply.It says...

  • single phase reversable motor wires

  • I just let all of the smoke out of the switch box from a single phasereversable...

  • Power line spikes / surges

  • We get a lot of frost where we are located. As the frost melts off the power...
  • « previous thread

  • joining the ends of thermocouple wires

  • i am trying to join the ends of the thermocouple wire and glue it to the nitinol...
  • next thread »

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.