Distribution Transformers


DELTA STAR three/single-phase distribution transformers, manufactured in accordance with NEMA standards, are economical power equipment with advanced winding design features for reducing no-load and load losses.

High-grade silicon steel is used for the core. Special treating methods to obtain greater di-electric and insulating strength and ensures durability.



A. Low Transformer Loss

High-quality cold rolled, grain-oriented silicon steel is used core designed for the most efficient power transformation, resulting in greatly reduced values of no-load losses.

B. Special design for continuous overload

Highly heat resistant insulation paper is used in between windings. Though the rated temperature rise of these transformers is 66° C at 100% continuous load operation. The actual temperature rise of Delta Star Distribution Transformers by test is only 55° C at full load operation. Thus these transformers can be operated under continuous overload until the temperature reaches 65° C.


A. Tests

Each Delta Star Distribution Transformer is given the following tests to ensure high quality.

  1. Voltage ratio and polarity test.
  2. Insulation resistance test.
  3. No-load test (Exciting Current and Core Loss)
  4. Load test (Impedance and Winding Loss)
  5. Temperature rise test.
  6. Noise level test.
  7. Construction Check

B. Basis of Performance

1. Service condition

For best performance the ambient air temperature should not exceed 50° C and the average ambient air temperature for any 24-hour period should not exceed 30° C. The transformers are designed for operation at an altitude of 1,000 meters or less.

2. Temperature rise

The temperature rise above the ambient temperature will not exceed the next value.

Winding Resistance Method 65° C

3. Vector Symbol/Primary-Secondary Winding Connection

Primary to secondary winding connections can be chosen on any of the following configurations as per customer's specifications :

a.) delta-delta

b.) delta-wye

c.) wye-delta

d.) wye-wye