Production

WINDINGS

    Cylindrical coils, which have more strength against the loads in short circuit conditions, are used in power and distribution transformers. Windings have got two different parts as follows;

  • LV Windings: Low Voltage Winding Conductor material is copper and the windings are made in the form of foil or paper insulated flattened type.
  • HV Windings: High Voltage Winding Conductor material is copper and the windings are made in the form of enameled round or paper insulated flattened type.

CORE

    The core transformers are made of cold rolled grain oriented silicon steel. Cores are produced by using first class quality of steel. According to specifications of transformers, cores are manufactured from magnetic silicone still sheets (metal sheet with silica) with low loss and directed particles. We use M3 (0,21 mm), M4 (0.27 mm) and M5 (0,30 mm) as the main core materials; and from time to time high permeability grade materials like MOH, ZDHK are also used. Cores are cut to lengths without burr by modem transformer lamination "cut-to­ length" machines. The cores are stacked without gaps and produced as step-lap, over-lap, 90° cut with or without holes.

ACTIVE PART AND COVER

    The assembly of core and coil is designed to increase the resistance against short circuit forces. The top cover, including the active part of standard transformers, is mounted to the tank with bolts. Another application is the direct assembly of active part to the tank.
    The connection parts of the top cover, the high voltage bushings, and the arching horns are made of stainless materials or of materials covered by a special coating which is resistant to corrosion. The arrangement of the bushing, the accessories, the protection box or the cable box is done on the top or the side of the transformer according to customer requests.

TANK

    Tanks and top covers for transformers are made of mild steel. The cooling surfaces of distribution transformers are made of corrugated walls; and they also form the sides of the tank. Bottom plate, sides and frame are sealed by welding.
    For transformers up to 4,000 kVA, corrugated cooling walls can be used as cooling surfaces. Also, it is possible to use radiators as cooling surfaces. Every transformer tank needs to pass an oil leakage test after welding. Therefore, each tank is taken under pressure after being produced. It is possible to enclose the bushings on the top cover into a protection box made of appropriate steel according to IEC 60144.

PAINT

    Transformers are in the colour of RAL 7033 as a standard. Transformer tanks are painted by the method of spraying. Method of painting is chosen in accordance with customer requests and working conditions of the-transformer.
    NOVA TRANSFORMER offers different applications, different thickness of film or transformers with different colours as per customer requests. Also, if requested, hot dip galvanized tanks can be produced.

DRY AND FILLING

    The active parts of transformers such as core and coils are dried under high vacuum in a furnace. The process of drying varies according to transformer's type, power and voltage. Oil is filled under high vacuum.

ACCESSORIES

    The followings accessories are mainly used to protect transformers;

  • Oil Level Indicator: Magnetic Oil Level Gauges are used in order to follow and to control the oil level in the conservator of transformers. Oil level indicators give alarm and tripping signals in case of sudden changes of the oil level.
  • Air Dehumidifier: Air Dehumidifier are utilized for transformers with oil conservator. The Air Dehumidifier is connected to the oil conservator. Via silicagel, it removes moisture and dust coming into the conservator. The amount of silicagel depends on the amount of oil inside the transformer.
  • Oil Thermometers: Oil Thermometers, which are located in thermometer pockets and welded on the top of the cover or on the side of the tank, gauge and control the maximum temperature of the oil. It 'is available with a maximum pointer, without electrical contact or with single or double electrical contacts. If the temperature exceeds the estimated values, thermometers with contact give alarm or tripping signals.
  • Buchholz (Gas Collecting and Alarm) Relay: The Buchholz-Relay collects the gasses, which are formed by discharges or arcs with low or high intensity inside the transformer. It is used for transformers with conservator. The relay can be with single or double contact.
  • Pressure Relief Device: Even though hermetic protection relay is used in transformers, pressure relief device is used additionally. It helps to cover the pressure that expands inside of the transformer.
  • Hermetic Protection Relay: Hermetically sealed transformers at a rate equal to and greater than 630 kVA are equipped with a Hermetic Protection Relay. It consists the functions of Oil Level Indicator, Temperature Indicator, Buchholz-Relay as well as Pressure Relay.
  • Alcohol Thermometer: Alcohol thermometer 1s only used to monitor the temperature of the transformer oil.