1. Transformer Rating and Efficiency:
· When a transformer is rated at 100 kVA (kilovoltamperes), it means that it can supply up to 100 kVA of apparent power under ideal conditions.
· However, the efficiency of a transformer (the ratio of output power to input power) is not always 100%. If a transformer has an efficiency of 90%, it means that 90% of the input power is converted to useful output power, while 10% is lost as heat or other forms of losses.
2. Understanding Derating:
· Derating a transformer means reducing its operating capacity to ensure it operates efficiently without overheating or becoming overloaded. A derating factor of
0.9 means the transformer should operateat 90% of its rated capacity to ensure optimal performance.
· For a 100 kVA transformer with a 0.9 derating factor, the effective capacity is 90 kVA. This is the maximum load you should connect to the transformer to maintain its efficiency and avoid overloading.
2. Calculating the Load Capacity:
· If you connect a load higher than 90 kVA to a 100 kVA transformer with 90% efficiency, the transformer operates beyond its derated capacity.
· For example, if you connect a load of 95 kVA:
· The load (95 kVA) exceeds the derated capacity (90 kVA).
· Operating at 95 kVA will cause the transformer to run inefficiently and
potentially overheat or experience higher
losses.
· Conclusion: Importance of Selecting the Correct Transformer Size
Why Choose a Transformer at 90% Efficiency?
· When selecting a transformer, consider both the rated capacity and its efficiency to ensure it can handle the desired load without issues.
· Choosing a transformer with a capacity at or below 90% of its rating ensures it operates within its efficiency range, minimizes losses, and prolongs its lifespan.
· For a 100 kVA transformer with 90% efficiency and a 0.9 derating factor, you should ideally connect loads up to 90 kVA and not exceed this limit to avoid overloading.