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Squirrel cage motor - damaged rotor of the squirrel cage motor

pakito1206 9252 10
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Treść została przetłumaczona polish » english Zobacz oryginalną wersję tematu
  • #1 16475119
    pakito1206
    Level 6  
    Hello,
    I have a 1.5 kW squirrel-cage motor, when idling (without load) it consumes a maximum of 4 A and heats up quite a bit. The resistance and connections of the windings are correct. Insulation resistance as well.
    What could be the reason for the consumption of such maximum current?
    Possible damage to the rotor of this motor? If so, how to check it?
    Thank you for your help.
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  • #2 16475125
    karolark
    Level 42  
    Bearing condition? rotor runout?
    Show the photo of the windings.
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  • #3 16475131
    MARCIN.SLASK
    Home appliances specialist
    Is the current on each phase the same?
    In the event of a cage break, the rotor will heat up.
  • #4 16475184
    pakito1206
    Level 6  
    The bearings are new, there is no rotor runout, the caps are good, the current is the same in all phases. All that remains is to check the rotor for a break. Has anyone tried to check it? Visually, it looks as if the core has been slightly shifted and someone has hit it before.
  • #5 16475187
    Krzysztof Reszka
    Moderator of Electrical engineering
    You can see that the bearings were gone, the rotor is already damaged. Stator packages probably in the same condition.
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  • #6 16475197
    pakito1206
    Level 6  
    How can I check the rotor is it really damaged?
  • #7 16475266
    Krzysztof Reszka
    Moderator of Electrical engineering
    In your case, visual observation is sufficient.
    Here is a photo of a good rotor, compare.
    Squirrel cage motor - damaged rotor of the squirrel cage motor
  • #8 16476383
    Berend
    Level 17  
    The rotor can be checked in several ways, including by removing the rotor and measuring whether the same current flows through each rod, or by measuring the amount of current flowing through the stator winding and then performing a fast Fourier transform in some program, this way is the best and non-invasive, but there are also many other ways.
  • #9 16476588
    Krzysztof Kamienski
    Level 43  
    Berend wrote:
    The rotor can be checked in several ways, including by removing the rotor and measuring that the same amperage is flowing through each rod
    You dont say ? Drill holes in the rotor and connect an ammeter? :D
    Personally, maybe twice in my life I have come across a damaged rotor in a three-phase asynchronous motor. However, when I suspect that the insulation of the "cage" is damaged, I examine it this way: I connect three stator windings in series and supply voltage of a dozen or so volts of alternating current through an ammeter, slowly turning the rotor by hand. current, I assume the rotor is electrically efficient.
  • #10 16477164
    Berend
    Level 17  
    Krzysztof Kamienski wrote:
    Berend wrote:
    The rotor can be checked in several ways, including by removing the rotor and measuring that the same amperage is flowing through each rod
    You dont say ? Drill holes in the rotor and connect an ammeter? :D
    Personally, maybe twice in my life I have come across a damaged rotor in a three-phase asynchronous motor. However, when I suspect that the insulation of the "cage" is damaged, I examine it this way: I connect three stator windings in series and supply voltage of a dozen or so volts of alternating current through an ammeter, slowly turning the rotor by hand. current, I assume the rotor is electrically efficient.




    Haven't heard about the induction method?

    An alternating current electromagnet with dimensions adjusted to the slot scale induces voltage in the individual bars of the rotor, if the bar has a connection with both rings, then a current flows in it, this current can be measured by a sensor (detector) which works on the principle of Dica bricks, where the magnetic circuit in this sensor is closed by the teeth adjacent to the tested bar and the rotor yoke.
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  • #11 16477198
    grzeskk
    Level 35  
    The photos show that it is a fairly old motor from brothers from the east, 380V. Currently, there is 400V on the network, and maybe the author has more. Excessive heating may be due to higher voltage and saturated operation, not damage.

Topic summary

A user reported issues with a 1.5 kW squirrel-cage motor that consumes a maximum of 4 A while idling and heats up significantly. The user confirmed that the windings' resistance and insulation are correct, and the current is consistent across all phases. Suggestions for diagnosing potential rotor damage included checking for bearing condition, rotor runout, and visual inspection for any signs of damage. Various methods to check the rotor's integrity were discussed, including visual comparison with a known good rotor, measuring current through rotor bars, and using an induction method to detect faults. Additionally, it was noted that excessive heating could be attributed to operating at a higher voltage than the motor's design specifications.
Summary generated by the language model.
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