Your question reveals a misunderstanding of how a transformer works.
The primary current of a transformer is determined by the secondary current, not the other way around. When the secondary voltage is applied to a load, a secondary current flows, and its value is determined by the secondary voltage and the load impedance. This secondary current then determines the value of the primary current.
in welding machine, the transformer used is basically a current transforrmer. so by changing the tap of secondary side of transformer, we can increase or decrease the current in the transformer.
The secondary current is determined by the load, not by the transformer. For example, if the secondary voltage is 50 V and the load is 100 ohms, then the secondary current will be 0.5 A. If the load is 25 ohms, then the secondary current will be 2 A. It is important that a continuous secondary current doesn't exceed the rated secondary current of the transformer.
why does have to short-circuit secondary wire of current transformer ?
When working on a current transformer the secondary windings must be shorted. <<>> Properly loaded
There is no 'standard' output current from a transformer. The secondary (output) current depends on the load, and should not exceed the rated secondary current. To find the rated secondary current, you divide the transformer's rated volt amperes by the rated secondary voltage. The above cited answer need more descriptive ; a) V/Z = I, b) V/Z = I + Magnetizing current of the transformer taken from Primary side of the transformer.
in welding machine, the transformer used is basically a current transforrmer. so by changing the tap of secondary side of transformer, we can increase or decrease the current in the transformer.
This is the rated output of the transformer, obtained by multiplying the rated secondary voltage by the rated secondary current. And it's 'kV.A', not 'kva'.
No. A step-down transformer's secondary voltage is lower than its primary voltage. The secondary current is determined by the load, and this causes a higher current in the primary winding.
the current decreases.AnswerThe secondary current is determined by the secondary voltage and the load, not by whether the transformer is a step-up or step-down type. Once this is established, you can determine the primary current. Remember, the secondary current determines the primary current, not the other way around!
The secondary current is determined by the load, not by the transformer. For example, if the secondary voltage is 50 V and the load is 100 ohms, then the secondary current will be 0.5 A. If the load is 25 ohms, then the secondary current will be 2 A. It is important that a continuous secondary current doesn't exceed the rated secondary current of the transformer.
why does have to short-circuit secondary wire of current transformer ?
When the secondary of a transformer is opened, there is no longer any load on the transformer. There will be some current flowing in the primary winding, which is needed to induce the voltage in the secondary. This primary current is referred to as the "no load" current, and is indicative of the core losses in the transformer.
The current in the secondary winding of a transformer is not determined by the current flowing in the primary winding; rather, it is the other way around.The current flowing through the secondary winding of a transformer is determined by the load to which it is connected. The primary current can then be determined from the turns ratio.
When working on a current transformer the secondary windings must be shorted. <<>> Properly loaded
There is no 'standard' output current from a transformer. The secondary (output) current depends on the load, and should not exceed the rated secondary current. To find the rated secondary current, you divide the transformer's rated volt amperes by the rated secondary voltage. The above cited answer need more descriptive ; a) V/Z = I, b) V/Z = I + Magnetizing current of the transformer taken from Primary side of the transformer.
A transformer has a primary (Where the AC supply voltage is applied); and a secondary where a voltage is induced by a fluctuating magnetic field in the iron core of the transformer. The secondary voltage depends on the ratio of windings between the primary and secondary. Since the transformer can't manufacture power the product of the voltage and current at the primary exceeds that in the secondary. So if the transformer steps up the voltage in the secondary, the maximum current in the secondary must decrease. Similarly if the voltage is stepped down the maximum current increases in the secondary. There are always losses in this process so the power in is always somewhat less than power out.
The secondary current is determined by the load, not by the transformer. But the load current mustn't continuously exceed the rated current of the secondary winding. To determine the secondary rated current, you need to know the rated secondary voltage of the transformer, and divide 315 kV.A by this figure.Incidentally, the correct symbol for 'kilovolt ampere' is 'kV.A', not 'kva'.