No-Load Testing
For no-load loss and heat run testing, these sets provide clean power with accurate regulation and voltage control. Several configurations are available:
1500 or 1800 RPM 50-50 Hz or 60-60
Hz: When no frequency conversion or adjustments are required. Often part of a multiple-output set in conjunction with a 150-Hz or 180-Hz generator.
600 RPM 50-60 Hz or 60-50 Hz: When testing transformers at a rated frequency that is different from the local frequency.
Variable frequency: By using a variable-frequency drive and motor to power these sets, any output frequency in the 50 Hz to 60 Hz range may be selected. This set is most useful when either frequency may be used for testing.
MGG: For larger range requirements, like 50-to-180 or 50-to-200 Hz, it is most economical to use two generators, one 50-to-60 Hz and the other 100-to-200 Hz. These generators may be able to be driven by the same motor.
90 to 400 Hz Induced Voltage Testing
These sets are used to energize the transformer at voltages exceeding its normal rating, in order to test its capability to withstand high voltages. They usually require low distortion and low partial discharge to permit detection of leakage in the tested transformer.
Special Application and Multiple Sets
For a more compact or economical installation, it is common to combine a nominal frequency generator and a high-frequency one with a common motor on the same base. Kato Engineering also supplies specialty M-G sets for testing of other equipment at frequencies from 25-1200 Hz, single or multiple phases (depending upon ratings).
- The generator can be designed to operate with either leading or lagging power factor while remaining stable even at full output.
- Frequency range/variable frequency: Normal frequencies are 50 and 60 Hz for no load tests, and either 150 or 180 Hz for induced-voltage tests. Smaller sets are available at 200 or 240 Hz, 300 or 360 Hz, and 400 Hz.
- By using a variable-frequency drive on the input, it is possible to build a set with wide frequency range such as 100-200 Hz, which may be advantageous for tuning the test system to a resonant frequency. A more than 2:1 frequency range is usually not economical, however.
