Objective: To perform Sumpner’s test. Predetermination of performance characteristics and equivalent circuit of single-phase transformer.

Preview: In OC and SC tests a transformer is subjected to either core loss or copper loss and so these tests cannot as such be used for heat-run for heat-run-test. A heat-run test can be conducted on two identical transformers by connecting them back-to-back. Wherein, their secondaries are connected in phase opposition. So the secondaries will behave open-circuited when the primaries are excited, the current drawn from V1 source being 2I0 providing core losses (2P0) of the two transformers. A low-voltage variable source V2, is connected in the secondary circuit which causes circulating current in the secondaries with primaries acting as short circuit for this source (use superposition theorem). This circulating current can be adjusted to full-load value. The power injected by this source is 2PC, the full-load copper loss of both transformers, while the impedance seen by it is 2Zeq. Both the transformers in this test are thus subjected to full load core and copper losses by phantom loading, while drawing only core loss power from source V1 and only copper loss power from source V2. In some sense this test has similarity with the Hopkinson’s test on two identical dc machines.

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. Transformer 1¢ 1KVA Capacity, Primary: 230V Secondary: 115V – Two numbers
2. Suitable Variac
3. Suitable digital ammeters of different ratings AC
4. Suitable digital voltmeters of different ratings AC
5. Suitable digital wattmeter