Surge Comparison Test
The Surge Test is highly important. That’s because 80% of all electrical failures in the stator begin at weak insulation turn-to-turn. Regardless of an individual’s personal view of Surge testing, knowing that a motor’s turn-to-turn insulation is sound is crucial for safety and motor reliability.
During a Surge Test, the equipment will charge up a capacitor inside the unit and dissipate it into one phase while holding the other two phases to ground. Then, automatically, the test unit will slowly increase the voltage from 0 volts to the target test voltage. This generates a waveform, in a shape based upon the inductance of the coil that is displayed on the test equipment screen. If the target test voltage is attained without any frequency change in the waveform, the turn-to-turn insulation integrity has been realized.
Paschen’s Law states that two bare wires placed next to one another just a thickness of a hair away need a minimum of 325 volts to jump the air gap between the two conductors. These two concepts are the core reason why Surge testing is the natural choice for testing turn-to-turn insulation. The main reason is that if the test equipment doesn’t produce a potential difference between the turns above Paschen’s Law, the current cannot flow through the fault. If current can’t flow through the fault, it will continue through all the coils and not show a difference.
Surge comparison tests are widely applicable for AC motors, DC motors, transformers, coils, wires, cables, capacitors etc.
The following list reflects problems you’re seeking to uncover and eliminate.
- Different size diameter copper between phases
- Unbalanced turn count between phases
- Reversed coils
- Shorted laminations