[Transformer] Turn ratio experiment
Purpose
· Compare with NSX data to evaluate possible damage in the magnetic circuit or coil.
· Is a condition for transformers to operate in parallel.
Method
· Two Voltmeter method
+ 1-phase MBA : Apply 1-phase AC voltage to the high coil, measure the value on two Voltmeters simultaneously, the variable ratio is calculated by: k = U AX /U ax . Perform on all voltage levels
+ 3-phase MBA : Apply 1-phase AC voltage to the high coil, measure values on two Voltmeters simultaneously. With the following other wiring groups, there are different connection methods and conversion factors.
For example: With the triangle - star - 5 (Dy5) wiring group, the experiment is as follows:
Phase A: The high side connects A – (B + C) (B is short-circuited with C), the low side connects ab, the ratio is calculated as follows: k = U A-(B+C) /2U a-b
For other wiring groups specified in the following table (refer to the OMICRON CPC 100 device user manual):
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· Ratio demand method:
The bridge circuit is as follows:
When the DET needle is balanced, the MBA ratio will be equal to R/R 1
Evaluate
The ratio error does not deviate more than 0.5% from the machine mark on all phases