- Efficiency is maximum at a load factor at which iron losses are equal to copper losses
- Efficiency changes with load factor
- The average load factor of a typical power transformer used in distribution system is about 0.5 and those used in generating station and major sub station is 0.8
- For maximum efficiency with 50% load factor, copper losses should be 4 times the iron losses
- Even on higher loads, the efficiency would be above 96 %
- The efficiency reduces rapidly at lower loads than the load for maximum efficiency
- While designing a transformer, the weight of iron and copper are selected such that copper loss is equal to iron loss for average transformer load factor. This ensures high ή during the operation
Definitions CSD (Controlled Switching Device): A device that is installed at the relay and control panel to overcome the transient behaviour of voltage and current during switching. This device synchronizes the switching of each pole of the circuit breaker according to the zero crossing of the corresponding phase. This device is also known as a phase synchronizing device, or PSD for short. Requirement When we switch off an online circuit breaker to disconnect an inductive load, we ideally want to interrupt the current of the system at the zero crossing of the current waveform. However, this is practically impossible to achieve. In a normal circuit breaker, the current interruption may occur near the zero crossing point, but not exactly at it. Since the load is inductive, this sudden interruption of current causes a high rate of change of current (di/dt), which results in a high transient voltage in the system. In low or medium voltage power systems, this transient voltage during circui...