The most sensitive part in rotating machines is the insulation. The expected lifetime of a stator winding depends on the ability of the insulation to prevent winding faults.
High temperatures and high rates of temperature changes can generate micro-voids particularly at the interface between mica and resin, and between semi-conductive layers and resin. Partial discharges in these voids will further increase the void size by erosion and complete breakdowns are inevitable.
Therefore, experts strongly recommend the checking of insulation for partial discharges during the whole lifecycle of motors and generators. In order to check the insulation a compensated high-voltage source is needed. The Omicron CPC 100 Multi-functional Primary Test System,and Omicron CP TD1 test system can be utilized as a high-voltage source.
As maintenance tools for entire windings, the “Δ tan δ” test and the tip-up test are used. Both tests are an indirect way of determining if partial discharges (PD) are occurring in a high-voltage stator winding.
An increase of the power factor / dissipation factor (tip-up) from the normal level indicates that the winding has significant PD activity, as this is indicative of this condition. The CPC 100,and CP TD1 test system allow “Δ tan δ” and tip-up tests complying with the IEC 60894 and IEEE 286 specifications.
An acceptable power / dissipation factor offers assurance that the coil or the bar were properly fabricated with inherently low-loss materials.
Rotating machines diagnosis
• Power / dissipation factor (tan δ) tip-up test at 50 Hz / 60 Hz up to 12 kV | max. 1 μF / 4 A| with CP TD1
• Power / dissipation factor test with variable frequency up to 12 kV | frequency from 15 Hz to 400 Hz | with CP TD1
• HV source for testing rotating machines up to 12 kV | max. 2 μF | with CP TD1
This is part of the Omicron CPC 100 All-In-One Test System Series. Check out the other posts!