Explainer video · TEMISA
Medium voltage motor rewinding: ground fault and VPI
Short answer
A ground fault is a coil touching the core after mica fails from heat, moisture and dust. TEMISA measures insulation resistance, polarization index and the core. Form-wound coils use copper strap and mica tape, then vacuum-and-pressure impregnation (VPI). The close is surge, hipot, rotor balancing and an EASA AR100 record, on medium- and high-voltage motors up to 13.8 kV.
Key points
- A ground fault is a coil in contact with the core.
- Diagnosis: insulation resistance, polarization index and a core test.
- New form-wound coils are made in the shop, with copper strap and mica tape.
- Impregnation is resin under vacuum and pressure (VPI).
- Final tests are insulation, surge and hipot, plus rotor balancing, documented to EASA AR100.
Transcript
Your 6,600-volt motor tripped its protection, and the line is down. So what happened inside? The stator carries copper coils insulated with mica. Over the years, heat, moisture and dust break down that insulation, until a coil makes contact with the core: a ground fault. Here's how we fix it at TEMISA. First, diagnosis: insulation resistance, polarization index and a core test, to know if the iron can be saved. Then we strip the damaged winding and build new form-wound coils in our own shop, with copper strap and mica tape. We insert them, connect them and impregnate them with resin under vacuum and pressure: VPI. Then we test: insulation, surge and hipot, and we balance the rotor. Your motor comes back tested and documented, to the EASA AR100 standard. At TEMISA we repair and rewind medium and high voltage motors, up to 13.8 kV. Get a quote at temisa.mx
Frequently asked questions
What is a ground fault in this motor?
A stator coil makes contact with the core. Heat, moisture and dust break down the mica insulation until that path appears and the protection trips. The motor in the video is 6,600 volts.
Which tests come before the rewind?
Insulation resistance, polarization index and a core test. The core test answers whether the iron can be saved.
How is the stator rewound?
The damaged winding is stripped. New form-wound coils are built in TEMISA's own coil area, with copper strap and mica tape, then inserted, connected and impregnated under vacuum and pressure (VPI).
What is checked before the motor goes back?
Insulation, surge and hipot, and the rotor is balanced. The motor is returned tested and documented to the EASA AR100 standard.
What voltage does the video cover?
Medium- and high-voltage motors, up to 13.8 kV. Send the nameplate to ventas@temisa.mx for a quotation.
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Request a quotation by email: ventas@temisa.mx. Phone: +52 33 3614 2460.