Surge voltage testing is used to discover insulation problems in wound materials. In studies, experts have determined that 60% of motor failures start out as coil shorts within a winding. A surge voltage test is the only testing method that can determine insulation problems in wound materials between windings.
How does a surge test work ?
During a surge test, a surge capacitor connected in parallel to the winding to be tested is discharged suddenly. A sinusoidal damped oscillation is created in the oscillating circuit created between the testing device and the winding, and this oscillation has a certain characteristic.
A surge test detects a fault between turns by observing a jump in the resonant frequency of this lc tank circuit. If the voltage produced by the surge is greater than the weakened dielectric strength of the turn insulation, one or more turns may be shorted out by arcing. The surge comparison test finds shorts insulation weaknesses in coils, windings, electric motors, generators, alternators, and transformers. These faults are typically turn-to-turn, coil-to-coil, or phase - to - phase.
The surge test is the most efficient way to find turn insulation weaknesses. For those who manufacture or rewind motors, being able to manufacture coils free of insulation defects is paramount to reliability.
System switching transients can be separated into transients associated with :
Major power system switching disturbances, such as capacitor bank switching; minor switching activity near the instrumentation or load changes in the power distribution system; resonating circuits associated with switching devices, such as thyristors;
various system faults, such as short circuits and arcing faults to the earthing system of the installation.
The major mechanisms by which lightning produced surge voltages are the following :
A direct lightning stroke to an external circuit (outdoor) injecting high currents producing voltages by either flowing through earth resistance of flowing through the impedance of the external circuit;
An indirect lightning stroke (i.e. A stroke between or within clouds or to nearby objects which produces electromagnetic fields) that induces voltages/currents on the conductors outside and/or inside a building;
Lightning earth current flow resulting from nearby direct-to-earth discharges coupling into the common earth paths of the earthing system of the installation.
The rapid change of voltage and flow of current which may occur when a protector is excited may couple into internal circuits. Test voltages of up to 4 kv are applied synchronized to the voltage phase at zero-crossing and peak value of the AC Voltage wave (positive and negative). The surges are applied line to line and line to earth. When testing line to earth the test voltage is applied successively between each of the lines and earth. All lower levels including the selected test level is tested.
Surge Tests can identify following flaws
Phase-to-Phase Weaknesses and Shorts (1)
Turn-to-Turn Weaknesses and Shorts (2)
Coil-to-Coil Weaknesses and Shorts (3)
We can assist in concerned CE Certification and Documantation. We can carry out tests suitable for gaining CE Certification, Useful for certification of Medical Devices, Household appliances test
