This is the current level needed to energize a transformer to its rated voltage
The clue is in the name! 'Excitation' means to create a magnetic field. So the excitation current is the current drawn from the supply which sets up the magnetic field around the core.
The transformer turns ratio meters is used to measure the excitation current. The excitation current is a magnetic field that is created from electric currents.
The turns ratio is the number of primary turns divided by the number of secondary turns. This is the same ratio as input current to output current. ie the turns ratio N = I1/I2
If it's a step up or step down transformer and you know the secondary side current, multiply the secondary current by the turns ratio. If you know the power in the secondary winding but not the current, divide the secondary power by the secondary voltage to get the secondary current and then multiply the secondary current by the turns ratio to get the primary current. The turns ratio is the number of turns on the secondary winding divided by the number of turns on the primary winding. For a step up transformer, the turns ratio will be greater then one. If it's a step down transformer, then the turns ratio will be less than one. If you don't know the turns ratio, divide the secondary voltage by the primary voltage to get the turns ratio.
For an ideal transformer, the voltage ratio is the same as its turns ratio.
RATIO ERROR The secondary current is less than the expected value. The secondary is less in magnitude. This diffence is known as ratio error. PHASE ERROR The angle between the expected and actual secondary current is known as phase error.
The secondary (output) voltage is determined by the primary voltage and the turns ratio of the transformer. The secondary current is determined by the secondary voltage and the load resistance.
Transformer turns ratio
The turns ratio is the number of primary turns divided by the number of secondary turns. This is the same ratio as input current to output current. ie the turns ratio N = I1/I2
It's approximately the inverse of the voltage- or turns-ratio:
with an ideal electrical transformer with an input current of 2 amps and an output current of 1 amp what is the turns ratio of the secondary and primary coils
The primary current on a loaded transformer depends on the secondary current, which is determined by the load. So, if you know the secondary load current, then you can use the turns ratio of the transformer to determine the primary current:Ip/Is = Ns/Np
If it's a step up or step down transformer and you know the secondary side current, multiply the secondary current by the turns ratio. If you know the power in the secondary winding but not the current, divide the secondary power by the secondary voltage to get the secondary current and then multiply the secondary current by the turns ratio to get the primary current. The turns ratio is the number of turns on the secondary winding divided by the number of turns on the primary winding. For a step up transformer, the turns ratio will be greater then one. If it's a step down transformer, then the turns ratio will be less than one. If you don't know the turns ratio, divide the secondary voltage by the primary voltage to get the turns ratio.
For an ideal transformer, the voltage ratio is the same as its turns ratio.
The turns ratio of a transformer is the number of primary turns to secondary turns. This defines how the transformer will change the voltage and current. For N1 primary turns, and N2 secondary turns, N1/N2 will be the turns ratio; the secondary voltage will be:the primary voltage x (N2/N1); The secondary current will be:primary current x (N1/N2)
RATIO ERROR The secondary current is less than the expected value. The secondary is less in magnitude. This diffence is known as ratio error. PHASE ERROR The angle between the expected and actual secondary current is known as phase error.
A current transformer is just a transformer designed to dutifully give an output related to turns ratio 1:xx.
The primary current is determined by the secondary current, not the other way around. For example, a step up transformer will step up the primary voltage in proportion to the turns ratio of the transformer. Any secondary current is then determined by the secondary voltage and the load, NOT by the primary current. The primary current is then determined by the secondary current in proportion to the reciprocal of the turns ratio.
Power flowing into a transformer must match the power flowing out (minus losses which are minimal). If this is not the case, there's something wrong. Differential protection monitors current only; Current flowing into one side of the transformer will be equal to current flowing out the other side scaled by the turns ratio of the transformer. Since the turns ratio is equivalent to the voltage ratio, this is easily set.