Effectively removing the moisture from the cellulose insulation is a key process in the production of Power and Distribution transformers and to ensuring the trouble-free operation of the transformer for years of service. Therefore quality of the drying of the insulating material is critical in meeting dielectric requirements and assuring trouble free service for users. Having understood that the amount of aging depend on the amount of moisture left in the cellulose insulation after manufacture , as the first manufacture in the region, the Low Frequency Heating (LFH) technology ( Hedrich Germany) was introduced to LTL’s process recently. This LFH system comes with automatic Oil filling and pressure testing facility which increases the efficiency and accuracy of the process drastically.
LFH process heats the transformer HV and LV windings uniformly from the inside by applying a low frequency current at low voltage levels through the HV winding while the LV windings remain short circuited. The Vacuum level of the chamber is precisely controlled throughout the process while monitoring the winding resistance through which the temperature of the winding is estimated.
Advantages of LFH :
- Drying time is more than 75% shorter as with hot air process
- Provides short process time, 5 hours for 3 phase transformers up to 500 kVA and 6 hours for transformers up to 2000kVA
- LF process allows direct oil filling for the transformers after drying no waiting time like in Hot air process
- Save at least 90% of energy compared with hot air process
- Average of residual moisture of the paper insulation is much below 0.3%
- ZERO time delay between drying and oil filling
Core Cutting Machine :
The most important part of the transformer is the active part which comprises windings and magnetic cores.
The transformer core is made from high-quality, cold rolled grain oriented silicon steel laminations. LTL is having a fully automated, state of the art GORG core cutting line with the worlds’ best technology for cutting of step lap cores coming from Germany. Step lap cores are having definite advantages over conventional cores.
Advantages of step lap cores :
- Reduce air gaps and prevent boundary areas from saturation.
- Reduce no-load current and no-load loss.
- Reduce the noise level
High Voltage Winding Machines :
In LTL, for High voltage windings, we are using winding machines from Tuboly-Astronic of Switzerland. These machines benefit from the latest technology and integrated systems to ensure for a smooth and ergonomically-optimized coiling process and an end-product that can save on costs. The coil winding process is fully automated on the wire winding machine from start to any programmed stopping point, which has vastly improved consistency of the wound wire and reduced the chances of coil impairment. The insulation between layers consists of thin strip insulation papers that give more compact winding design.