Stator
Shorted Turns - Case History 5 LV, 3-Phase Induction Motor - Inverter Fed (a VSD) |
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Background
and Test Objective However, it was important to carry out tests out on an inverter fed SCIM. An 11 kW motor of the same design and rating was used but it was fed from an inverter and had a double layer lap winding. For the tests a complete coil was initially short circuited via an external limiting resistor. To predict
current spectra with and without shorted turns in the stator winding of
an inverter fed SCIM. |
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Nameplate
details |
Additional
Information 36 slot stator, double layer winding, 8/9 coil pitch, 180turns/phase, 15turns/coil, Number of rotor slots = 51 (aluminium die cast). Direct drive coupling to a d.c. dynamometer load machine. Full-load slip = 0.04 |
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Test
Conditions MCSA FFT Current Spectrum, 0-200Hz span Dynamic Range = 80dB Frequency Resolution = 0.5 Hertz/line |
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Figure s-20 Time domain current spectrum from inverter fed SCIM |
Figure s-20 shows the input current waveform to the motor supplied from the PWM inverter. | |||||
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EXPERT COMMENT This case history shows that MCSA can also detect shorted turns in a stator winding fed from an inverter. The short circuit current was limited to prevent motor burn out but as was shown in Shorted Turns Case History 2 the components would rapidly increase in magnitude as the severity of the fault increased. |
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EM
Diagnostics Ltd, |
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