How much power does a transformer consume when Idle?
All transformers consume power when they are connected to a line and there is no-load connected to the secondary. This amount of power is very small in comparison to the KVA rating of the transformer. This power consumed is commonly referred to as the no-load losses. These losses run on the order of 1% or less for most small and medium size transformers; for example, a 25 KVA, single phase, 60 cycle, 480 volts to 120/240 volts transformer would have a no-load loss of about 150 watts or .6% of the name plate rating of the transformer. This loss appears in the form of heat and is confined to the iron or lamination of the transformer. Such loss relates to the level of exciting current necessary to make the transformer operative.
All transformers consume power when they are connected to a line and there is no load connected to the secondary. Small in reference to the KVA rating of the transformer, these “no load losses” are approximately 1% or less for small and medium size transformers. The losses appear in the form of heat in the iron or laminations of the transformer. The losses are in relation to the level of exciting current necessary to make the transformer operate.
