Main Question or Discussion Point
What are the two methods for calculating large DC motor efficiency ?
What about Swinburne’s Test and Hopkinson’s Test ?. Can they be used for calculating large Machine efficiency?For a reasonable estimate at full power rating:
Example: 400 HP. 1750 RPM. 500V/633A armature. 300V/4.84A shunt field.
- Record motor nameplate values.
- Calculate electrical power required by the shunt field, and armature power. Add them together.
- Divide mechanical output (shaft) power into the electrical power required to generate it.
316.5 kW + 1452 watts = 317.952 kW
400 HP = 298.28 kW
298.28/317.95 = 93.8%
Experimentally, design and build a suitably sized dynamometer (or haul the motor to a rewind shop large enough to have the requisite equipment), and couple it to the motor. Measure output shaft power while simultaneously measuring and recording armature and field voltage and current. Do the math.
Sure.What about Swinburne’s Test and Hopkinson’s Test ?. Can they be used for calculating large Machine efficiency?