Problems occurring at electric machines may result from electrical or mechanical causes. Electrical causes include faults in the windings, in the controller or in the electronics. The insulation resistance measurement detects insulation faults between the windings and to the housing. Inter-turn short circuits are readily detected within the coil by comparing the electrical characteristics of the windings in multi-phase machines with each other. Together with the COIL adapter XTRA, the METRAHIT IM XTRA or E-DRIVE can be used to conduct testing with a 1 kV surge voltage (surge test). In this way, defects are detected which only occur when operating voltage is applied.
Testing is possible for coils with inductances within a range of 10 μH to 5 H, which corresponds to nominal power from approximately 160 VA to 80 MVA for 3-phase machines with a nominal voltage of 400 V. The test sequence is semi-automatic – after connection to terminals U, V and W, testing is started with the help of a rotary switch. Compensation of remanence effects is also possible.
In the case of multi-phase electric motors and generators, e.g. 3-phase motors in accordance with DIN, asymmetries are detected directly at the windings by means of comparing the measurement results, thus making it possible to evaluate inter-turn short-circuits.
In the case of single-phase motors and generators, testing is based on a comparison with a known setpoint value.
Inter-turn short circuit measurement within the following inductance range with the Z270M adapter: 10 μH to 5 H at 100 Hz.
The Z270M adapter is universally suitable for many electric machines with various power ratings. For motors in accordance with DIN standards, this corresponds to power ratings of roughly 160 VA to 80 MVA.
- Simultaneous connection to 3 coils
- Rotary switch for coil selection • Polarity reversal via the rotary switch
- 2 inductance ranges 10 μH … 50 mH 5 mH … 5 H
- Combined connector plug for METRAHIT IM
- Automatic indication of rotary switch position to the METRAHIT IM
- Graphic representation of measurement values at the METRAHIT IM