logo elektroda
logo elektroda
X
logo elektroda
Advanced Search
logo elektroda

Using Inductor and Clamp Meter to Determine Electric Motor Overheating: Correct Current Values?

dragunow 78041 17
Best answers

How can I check whether an electric motor is overheated or damaged using basic tools, and what current values are correct at no-load or partial load?

First check the insulation resistance of the windings to the housing (you can measure all windings together); if it is above 1 MΩ for at least 60 seconds, the insulation is considered acceptable for this basic test [#9136707] After that, power the motor normally and measure the phase currents with a clamp meter; at no-load the current is typically around 40–60% of the rated current, and the currents on the three phases should be nearly the same, about within ±5% [#9127595][#9133105] One reply also recommends supplying the motor with undervoltage for safety while checking the current in each phase [#9131163] If the insulation is okay and the no-load phase currents are equal, the remaining fault in the described case may simply be the bearings, so replacing them is a reasonable next step [#9136707]
Generated by the language model.
ADVERTISEMENT
Treść została przetłumaczona polish » english Zobacz oryginalną wersję tematu
Report a violation of the law
| New topic
  • #1 9127498
    dragunow
    Level 9  
    Posts: 47
    Rate: 5
    Hello all.
    My question concerns the methods of checking electric motors with the use of basic instruments, i.e. an inductor and a clamp meter, at the moment he has these devices.
    I know that when using an inductor, you can check the impedance between individual coils and between the coils and the housing? But how to check the so-called "overheated" motor, what values of currents consumed by the motor are correct in idle or half the rated value ??? or maybe some other percentage ??

    Thanks for all valuable tips :)
  • ADVERTISEMENT
  • #2 9127595
    bonanza
    Power inverters specialist  
    Posts: 3097
    Help: 283
    Rate: 418
    Something like 50% of the rated current. And it should be the same on 3 phases (+/- 5%).
  • #3 9128749
    Krzyś33
    Level 25  
    Posts: 687
    Help: 58
    Rate: 104
    If you write about an inductor, you don't measure the impedance, but the resistance of the windings. (yes, in order to be correct). Greetings.
  • #4 9128844
    retrofood
    VIP Meritorious for electroda.pl  
    Posts: 31317
    Help: 1140
    Rate: 4781
    Krzyś33 wrote:
    If you write about an inductor, you don't measure the impedance, but the resistance of the windings. (yes, in order to be correct). Greetings.


    Resistance isolation windings.
  • ADVERTISEMENT
  • #5 9131124
    Roha
    Level 11  
    Posts: 24
    Help: 1
    Rate: 21
    Check the insulation resistance between the windings and between each winding and the body (casing).
  • #6 9131163
    Anonymous
    Anonymous  
  • #7 9131679
    stomat
    Level 39  
    Posts: 5600
    Help: 256
    Rate: 1953
    A burnt engine is very easy to spot with your nose.
  • #8 9132264
    dragunow
    Level 9  
    Posts: 47
    Rate: 5
    Thanks gentlemen for valuable tips :)

    In summary, with an inductor we measure the resistance between the individual coils and the resistance of each coil separately between the motor body.
    As for the measurement of the idle run, the rated current should be approx. 50% of the rated value +/- 5%.
    Anyone want to add anything else ??
  • ADVERTISEMENT
  • #9 9132522
    tolkien1980
    Level 18  
    Posts: 169
    Help: 32
    Rate: 21
    The winding insulation resistance can also be measured with a digital meter in the 200Mohm range. The meter should show no value (ideally).
  • #10 9132561
    Anonymous
    Anonymous  
  • Helpful post
    #11 9133105
    bonanza
    Power inverters specialist  
    Posts: 3097
    Help: 283
    Rate: 418
    bonanza wrote:
    Something like 50% of the rated current. And it should be the same on 3 phases (+/- 5%).

    What I meant was that the phase-to-phase dispersion was 5% and the no-load current could probably be 40-60% or wider.
  • #12 9133381
    retrofood
    VIP Meritorious for electroda.pl  
    Posts: 31317
    Help: 1140
    Rate: 4781
    dragunow wrote:

    My question concerns the methods of checking electric motors with the use of basic instruments, i.e. an inductor and a clamp meter, at the moment he has these devices.


    Anyway, what and why do you need it? Why don't you write anything about it?
  • ADVERTISEMENT
  • #13 9136598
    dragunow
    Level 9  
    Posts: 47
    Rate: 5
    And I'm already improving. I have an engine from the so-called recovery that worked in the lumber dryer. The motor was pulled off because the bearings started to rumble strongly.
    Well, but due to the difficult working conditions, i.e. moisture and temperature of about 80 ° C, I would like to be sure whether it is worth regenerating it, i.e. replacing the bearings and seals? Can such an engine still be used and how to check it?
  • Helpful post
    #14 9136707
    retrofood
    VIP Meritorious for electroda.pl  
    Posts: 31317
    Help: 1140
    Rate: 4781
    Check with the inductor the insulation resistance of the windings to the housing (you can all together). If it exceeds 1 MOma (for a minimum of 60 seconds !!!), then after switching to normal voltage, check whether the no-load currents on individual phases are equal. If so - replace the bearings. And that's it.
  • #15 9136731
    robokop
    VIP Meritorious for electroda.pl  
    Posts: 29406
    Help: 1760
    Rate: 6342
    And wouldn't it be easier to connect the motor to the mains for a few minutes and watch the temperature rise? Phase current imbalance at idling speed can occur and does not necessarily indicate a motor fault.
  • #16 9136827
    retrofood
    VIP Meritorious for electroda.pl  
    Posts: 31317
    Help: 1140
    Rate: 4781
    robokop wrote:
    And wouldn't it be easier to connect the motor to the mains for a few minutes and watch the temperature rise? Phase current imbalance at idling speed can occur and does not necessarily indicate a motor fault.


    In case of any suspicions, it is better (safer) to deal with the insulation resistance first. It's two minutes of work.
  • #17 9137635
    dragunow
    Level 9  
    Posts: 47
    Rate: 5
    Ok thanks for helping everyone.
    I take care of the measurements and the possible replacement of the bearings.
    I consider the topic closed.
  • #18 19310447
    gruniu
    Level 18  
    Posts: 925
    Rate: 176
    I found this topic, so I'm not starting a new one.
    How to check a single phase motor?



    Moderated By Krzysztof Reszka:

    3.1.19. Do not send messages on archival topics if this is another question, in particular other than the questioning person. Out of respect for the questioner, create your own topic. You can only add a solution to the problem.

    Same as three-phase.

| New topic
Report a violation of the law

Topic summary

✨ The discussion focuses on methods for assessing electric motor overheating using an inductor and a clamp meter. Key points include measuring the resistance of motor windings and insulation resistance between coils and the motor casing. It is suggested that the no-load current should be approximately 50% of the rated current, with a tolerance of +/- 5%. Participants emphasize the importance of checking insulation resistance, ideally exceeding 1 MΩ for safety, before applying normal voltage. Additionally, monitoring phase currents during idle operation can help identify potential issues, although phase imbalances may not always indicate a fault. The conversation concludes with advice on bearing replacement and the feasibility of using motors previously exposed to harsh conditions.
Generated by the language model.
ADVERTISEMENT