ST2883 Series Operation Manual Chapter 7 User guide
7-3
7.4 Technology application
7.4.1 Test objects
1.
Turn-to-turn and layer-to-layer short
Turn-to-turn short refers to the short caused by the insulation damage between turns. Layer-to-layer
short occurs in the coil consisting of multiple layers. There are two kinds of short: direct short and pull
arc short, both of which are shown as more dissipation.
2.
Bad coil
The different number of coils will cause the variation of inductance, which is reflected as the change of
oscillation period.
3.
Corona discharge
Due to the use of impulse high voltage, if the insulations between the coil and layer and terminal are not
strong enough, operator can observe the discharge and the corona discharge phenomenons. The corona
discharge that can be captured by the impulse winding tester has weak energy. Instead of influencing the
attenuation oscillation wave, it is only displayed as discrete jumping points around the waveform of high
potential.
4.
Material of magnetic core
Whether a magnet is used in the coil as the magnetic core or the magnet is poor, above conditions of the
magnet will influence the inductance and the dissipation. Likewise, if air gas is designed in the magnetic
core, the size of which will also have an impact on the inductance and the dissipation. Effects mentioned
above will show as changes of the attenuating vibration period and the attenuation degree.
7.4.2 Select comparison method
Area size comparison is mainly used to compare the energy consumption.
Differential area comparison is sensitive to energy consumption and inductance change.
Corona comparison method is the best one for testing internal insulation of the coil.
Differential phase comparison is the most suitable one to show the inductance difference.
To test turn-to-turn short or layer-to-layer short, it is recommended to use Area Size comparison.
Poor coil can be recognized by Differential Phase comparison.
The insulation performance has some impacts on the life span of the coil products. For this reason, when the
test occasion requires high standard of insulation performance, corona comparison must be switched on.
The material difference of magnetic core can be tested by Area Size comparison, Differential Area
comparison or Corona comparison.
Both Area size comparison and corona comparison can be used to test coils of motor, solenoid and relay. Area
size comparison, according to energy dissipation, can effectively detect layer-to-layer short and
circle-to-circle short, while corona comparison is mainly applied to detect coil’s internal insulation failure. If
it is required to test inductance, differential area comparison should be selected.
7.4.3 Settings of comparison method
Sample the standard wave by ways mentioned in 7.2.2 and turn on the required comparisons dealt with in
7.4.2. For area size comparison and corona comparison, the setting values are determined by the two methods
discussed below:
A.
①
If the condition is permitted, test10 to 20 samples.
②
Find out the entity that has the largest deviation value and then use it to make electrical test. If this
