Intermittent operation of the transformer
Transformers are designed for continuous nominal load. If a transformer is only loaded intermittently, its size can be reduced.
The intermittent use percentage can be determined with the following formula:
ED = [ton /(ton + toff)] x 100 %
- ED = time of intermittent use in percentage
- ton = transformer load time
- toff = transformer idle time
Transformers that are continuously loaded using nominal power (Pn) can be intermittently loaded with power ( P2) as follows:
P2 = Pn x √ (100/ED)
- P2 = allowed load in intermittent use (W)
The prerequisite of intermittent use is that the transformer’s warm-up time constant is significantly larger than the sum of load and idle times.