What is no load current in transformer?

Answer 1

I'm not sure that it is correct to say a transformer limits current under no load (maybe it is, depending on your application).

A step down transformer converts a high voltage at the primary to a lower voltage at the secondary. Under no load conditions, the secondary will be an open circuit. Since The primary current relative to the secondary current will be Np/Ns (the turns ratio, primary to secondary), and the primary voltage relative to the secondary is Ns/Np, the apparent resistance at the primary due to an open at the secondary will be (Np/Ns)^2*(open circuit). Since an open circuit is typically approximated as an infinite resistance, resistance is infinite. The turns ratio in this idealized example doesn't really matter, hence the transformer doesn't really matter (only the fact that a no load means an open secondary matters).

AnswerUnder no-load conditions, the primary current is limited due to the voltage induced into the primary winding, which opposes the applied voltage (Lenz's Law).

Answer 2

load is the key word. load means there is no device, for example motor,lights.speakers, ect. on th secondary side of the transformer, there are two components to a transformer. "primary & secondary" primary is the voltage that yoi have to supply the transformer and the secondary is supplying the new voltage to the component you want to energize. so if you do not have the secondary wired to a component,them you have no load current to read. check out ohms law for the definition for load. start with voltage and current then you get a load. turn off your lights when you leave the room cause your adding a current load tp your electric meter. hope this helps

Answer

With no load connected to the secondary winding of a transformer, the current flowing in the primary winding is called its 'no load current'. This no-load current is equal to the potential difference applied to the primary winding, divided by the impedance of that winding. As the resistance is very low compared to the inductive reactance, the resulting no-load current lags the potential difference by a very large phase angle. This no-load current can be resolved into two components: the first, which lags the potential difference at 90 degrees is called the 'magnetising current', and -as the name suggests- is responsible for setting up the flux in the core. The second, which is in phase with the potential difference, is accounts for the losses within the transformer.

With a load connected, this situation changes. The secondary current (the secondary voltage divided by the load impedance) is reflected back into the primary, where it increases the original no-load current, and alters its phase angle.