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 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.
Transformer cores are constructed with high grade, non-aging, grain-oriented silicon steel with high magnetic permeability and low hysteresis and eddy current losses. Maximum magnetic flux densities are substantially below the saturation point. The core volume allows efficient transformer operation at ten percent (10%) above the highest tap voltage. The core laminations are tightly clamped and compressed. Coils are wound of electrical grade fiberglass-coated aluminum with continuous wound construction. The coil assembly are impregnated with a non-hydmscopic, thermo setting varnish and cured to reduce hotspots and seal out moisture.
Low core loss and winding loss are thus guaranteed.
All insulation materials are flame-retardant and do not support combustion .
Transformers are insulated at 220 degrees Centigrade with 150 degrees Centigrade rise. Required performance are obtained without exceeding the above rise in a 40 degrees Centigrade maximum 30 degrees Centigrade average ambient temperature.
The enclosures are made of heavy gauge steel and are degreased , cleaned, primed and finished with gray color weather-resistant enamel.
On ventilated designs, the side enclosures are constructed with drip-proof louvers, with lifting holes. This ensures heat dissipation easily. All ventilation openings are protected against falling dirt.
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. TESTS
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. *
SPECIFYING THE TRANSFORMER NEEDED:
• 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.
• Fort three phase transformers, determine connection vector configuration.
Basically the above specifications are sufficient to determine the right transformer for your need.
THE FOLLOWING ITEMS MUST ALSO BE CONSIDERED IN SELECTING THE RIGHT TRANSFORMER FOR YOUR PARTICULAR APPLICATION:
Transformer taps compensate for high or low line voltages. Standard three phase taps are two (2) 5 percent taps below normal on all transformers. This arrangement provides a 10-percent range of tap adjustment. However, voltage tap arrangement could be designed as per customers' specifications.
IMPORTANCE OF SOUND LEVELS IN TRANSFORMERS
All transformers make some sound . .. due to the vibration generated within the magnetic steel core.
Fortunately, the noises in and around most locations - "the ambient sound level" - usually mask transformer sounds if certain precautions are taken in selecting and in installing the unit.
Not all noise can be heard!
To illustrate: you are riding in your car, the radio and heater are on. Everything's fine.. . . no annoying rattles.
If you turn the heater off, you hear slight rattles and squeaks. If you turn the radio off, you'll hear even more noises. The noises you hear were there all the time. . . which brings us to an important truth about sound: only the loudest sounds are heard. Still not convince? Shoot off a cannon and drop a pin at the same time. Which do you hear? And yet the pin did make a sound when it struck.
Let's illustrate this principle with transformers: a 50 db transformer located in a 60 db ambient noise level- say an office with typewriters chattering, telephones ringing - wouldn't bother anyone. The office noises drown out the humming of the transformer. But at night, the ambient sound level drops, and the humming becomes quite apparent.
Delta Star Transformers core are clamped tightly and coils are wound tightly. Thus sound level of Delta Star Transformers are guaranteed to conform with ANSI-C89 specifications.
DIMENSIONS & SPECIFICATIONS
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Dry Type Tranformers
Losses of Dry Type Transformers
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