What is the maximum efficiency achieved by modern distribution transformers?
With advanced materials and tight manufacturing controls, modern distribution transformers achieve a maximum (nameplate) efficiency of around 99% and an all-day efficiency of 98%.
Is transformer efficiency dependent on power factor?
Yes, the efficiency increases with an increase in power factor as copper losses reduce with a higher power factor while core losses remain the same. Maximum efficiency occurs at the unity power factor.
How does the load factor affect transformer efficiency
The higher the load factor, the better the transformer efficiency as the ratio of the no-load period to the loaded period decreases. Maximum efficiency is obtained at full rated load.
Why is all-day efficiency lower than maximum efficiency?
All-day efficiency considers no-load periods when only iron losses exist. Due to random variable loading, the average efficiency over 24 hours is lower than the maximum achievable efficiency at full load.
Which type of test is used to determine full load losses of a transformer?
A short-circuit test is used to determine full load copper losses, while a no-load (open-circuit) test gives core or iron losses of a transformer.