Cable Box

What is No-Load Current?

If a device without load is connected to a defined nominal voltage the no-load current is flowing. No-load current is also called idle. During idle a current may flow, which can lead to an undesired loss of energy.

Examples of Application for No-Load Current

Idle in an Electric Engine

An electric machine (engine, actuator) uses energy to move its own parts and to overcome friction and bearing resistance during idle. Inside of coils, additional loss of iron occurs through the stimulation of the electromagnetic field. This current increases the energy use of an application.

Idle in a Transformer

If the secondary side of a transformer is not occupied by an electrical consumer, the current flowing on the primary side is called no-load current. There can be a wide range depending on the manufacturing tolerances of the transformer core. Compared to the regular current under full load on the secondary side, the no-load current is very small. During idle, trial once the no-load current flows through the coil which is to be measured. During the trial the iron loss of the transformer can be determined.

During idle the majority of the received power is lost in the form of waste heat. Therefore idle losses should be kept as low as possible. By disconnecting from the network the no-load current is switched off and thus losses are avoided.