Delta Star power transformers are individually designed and manufactured to meet and exceed the highest industry standards and the exact specifications for the particular application involved. They are not stock units modified or customized to meet minimum specifications. Special options and features are planned into the original design and built into the unit. Delta Star power transformers are liquid-oil-immersed for the most efficient and reliable long-term operation in a wide variety of utility and industrial applications (transformer oil meets or exceeds ASTM D 3487 standards). Markets Served Utility Applications include power and distribution, system step up or step down transmission voltages, system tie, automatic voltage regulation, and many more. Industrial Applications include secondary load center, unit substation, distribution service, and power substation. Delta Star power transformers are manufactured in the medium to high voltage range from 5 kV up through 315 kV class in single and 3-phase ratings, 5 through 180 MVA (self cooled rating) with or without load tap change equipment. Power Generation Applications include generator step up, unit auxiliaries (UAT), and station service.
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Core

Each Delta Star power transformer core is designed to provide the accuracy and consistency necessary for high efficiency and superior performance. Only the highest quality grain-oriented electrical steel is used to make step-lap laminations cut to engineering design specifications. After the laminations have been precisely cut and assembled on a stacking table for accurate positions, experienced personnel assemble the core clamping structure so that the mass of steel is supported in a cradle-like method. The structure eliminates undue stress on the laminations while providing maximum strength to withstand the forces of shipping and short circuit.

Coil

Delta Star engineers custom design coils with the optimum winding configuration to meet the specific requirements of each application. Advanced engineering ensures high reliability, mechanical, and electrical integrity. Specific requirements such as non-standard loading conditions or low-impedance are accommodated in design. All Delta Star windings are designed and built with the inherent strength to withstand the axial and radial components of short circuit stress. The design calculations have been developed and proven by short circuit test results. Only the best grade electrical conductors and materials are used to make the coils of Delta Star power transformers.

Tank

Because long-term tank integrity is absolutely essential for the reliability and long life of a transformer, Delta Star fabricates transformer tanks to meet the highest standards of quality and craftsmanship. All tanks and covers are fabricated of high quality plate steel to withstand full vacuum. Tank corners are bent instead of welded to assure strength, reliability, and eliminate stress leaks. Welding is accomplished in a double shielded "mig" process that provides continuous welds. All tank seams are welded inside and outside to ensure leak-free construction. A leading paint manufacturer, after many years of research and development, has developed a special transformer paint formulated to withstand exposure to extreme weather conditions. Prior to painting, the metal surface is shot-blasted to provide superior cleanliness and paint bonding.

Control

At Delta Star, the control panel is given special emphasis in design and construction as the critical part to monitor, control, and protect the whole power transformer unit. Delta Star produces a superior control panel that enables the user to accurately monitor and adjust the operation of the transformer. Sensors are located at various points in the transformer to accurately monitor temperature, fluid levels, and other conditions of the unit at all times. Alarms and visual instruments alert personnel in the event of an abnormal condition for correction or further troubleshooting. Remote monitoring is also available.

Testing

Delta Star engineers conduct all routine tests, in accordance with ANSI/IEEE on every transformer manufactured. In addition to these routine tests, the Quality Control team performs ANSI/IEEE design tests including switching surge impulse, zero-phase sequence impedance, temperature rise, and sound level. Knowing that load and no-load losses over time can be a primary cost consideration, Delta Star provides certified test reports on every transformer and supports it with an instrument calibration program traceable to standards (NIST).

Service

Delta Star provides a full range of power transformer services through a highly qualified force of readily available field service engineers and technicians. Troubleshooting, technical assistance, and emergency repairs are prime examples of these services. Complete Delta Star services translate into cost savings, equipment compatibility, one source service responsibility, requirements coordination, and availability of computerized replacement parts inventory. Delta Star enables customers to conduct business with confidence and without interruption.

LTC/DETC

Tap changing equipment used on Delta Star transformers are available for off-load or load applications. Both type units have been developed and improved to exceed the highest industry standards and to provide long service life with minimum maintenance requirements. Off-load DETC units feature silver plated contacts and operate under spring-pressure to ensure positive contact. The tap changing control lever is operated externally. It clearly indicates the tap position and can be pad locked in the locked position. Load LTC units maintain the voltage at the load to the required level, automatically utilizing advanced technical design and the most durable high efficiency, long contact life, and maintenance-free operation (vacuum-reactor or resistor types are available).