Dry-Type Transformers

DELTA STAR Dry Type Transformers are rated 600 volts and below for supplying appliance, lighting and power loads from electrical distribution systems. Capacity ratings are available from 5 to 1500 KVA. Standard distribution voltages are 480 and 240 Volts; standard load voltages are 480, 380, 240, 208, and 120 volts. (However, other voltages as per customer's specifications can be made available in a case to case basis). The transformer is used to match the load voltage to the distribution voltage. Since no vaults are required for installation and they are housed in free-standing enclosures, these transformers can be located right at the load to provide the correct voltage for the application. This eliminates the need for long, costly low voltage feeders.

Delta Star Transformers are designed, manufactured, and tested in accordance with all applicable ANSI/NEMA & IIEE Standards.

All Delta Star Transformers are designed for continuous operation at rated KVA, 24 hours a day, 365 days a year.

All transformers are equipped with a wiring compartment suitable for conduit entry and large enough to allow convenient wiring. The maximum temperature of the enclosure does not exceed 90°C.

The core of the transformer is visibly grounded to the enclosure.


The following test are conducted on all transformers:

  1. Ratio tests on the rated voltage connection and on all tap connections
  2. Polarity and phase-relation tests on the rated voltage connection.
  3. Insulation resistance test.
  4. No-load and excitation current at rated voltage.
  5. Impedance measurement.


  • Determine the primary voltage - the source voltage presently available.
  • Determine the secondary voltage -  the voltage needed at the load.
  • Determine the KVA load, allowing room for expansion.
  • For three phase transformers, determine connection vector configuration.

Basically the above specifications are sufficient to determine the right transformer for your need.


Over the past years, new electronic equipment have been studied to produce harmonics that create non-linear current load which in turn generate extra heat in distribution transformer windings.

Technically-designed K-Rated Transformers by Delta Star are available to efficiently supply power to such various electronic equipment and neutralizing the problem of overheating.