HOPKINSON?S TEST

Objective: To conduct Hopkinson?s test on the given pair of identical dc machines and obtains item performance characteristics

Preview:
Swinburne?s test on a dc machine is a non-loading test. The machine performance can be computed from the data obtained from this test without actually loading it. In certain situations a dc machine has to be tested by actually loading it particularly for a heat-run test where the machine is fully loaded for a long period to determine its steady state temperature rise. Such a test may not be feasible for machines of even moderate size and such load test even where feasible is highly wasteful of energy for the heat-run test.

In a manufacturing concern a number of identical machines may be on production line. Two such machines can be put on a test and coupled mechanically. These machines can then be tested by the Hopkinson?s test where these two machines are connected in parallel across the supply. By adjusting their excitations both of them can be simultaneously loaded (to any extent) where one machine (motoring) feeds mechanical power to the other machine (generating), while the generating machine feeds electrical power to the motoring machine. The only power drawn from the mains is the losses of both the machines. Load test and heat-run test could thus be conducted with very little energy consumption while the machines carry full load current at rated voltage.

Equipment Required: All the measuring instruments associated with each experiment are industrial grade. These instruments are housed in an elegant cabinet as a package. Range of instruments and accessories (standard format)

1. 2HP Shunt machines mechanically coupled both are identical 220V 2HP 1500rpm.
2. 3-4 point DC Starter for the above
3. Suitable Loading rheostats
4. Digital tachometer
5. Suitable double tube rheostat
6. Suitable single tube rheostat
7. Suitable digital Voltmeters DC
8. Suitable digital ammeters DC.
9. Suitable DC source ?Rectifier unit