A 100 KVA transformer has a rated primary current of 10A and

A 100 KVA transformer has a rated primary current of 10A and a turns ratio of 10. What is the value of the primary voltage and the secondary current?

Solution

Given turns ratio Ns/Np = 10;

Given primary current Ip = 10 ;

We know that in a ideal transformer power tranfered is constant where as magnitute of primary voltage, current and secondary voltage, current vary but there product is constant i.e, equal to power transfer.

Vp*Ip = Vs*Is;

where Vp = primary Voltage;

Ip = primary current;

Vs = secondary Voltage;

Is = secondary Current;

From the above relation we conclude that in a transformer

Ns/Np = No of Secondary winding turns/No.of Primary winding Turns

Ns/Np = Vs/Vp = Ip/Is

Primary current Ip = 10 A ;

Secondary Current Is = Ip/(Ns/Np) = 10/10 = 1 A

Given power rating of transformer P = 100 kVA

we know that P = Vp*Ip = Vs*Is

Primary Voltage Vp = P/Ip = 100/10 = 10 kV

Secondary Voltage Vs = P/Is = 100/1 = 100 kV;