It is a transformer with No load attach to it.
Without a load the secondary current is zero, by definition.
A transformer will operate with a voltage regulation of zero when it is not supplying a load.
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.
why does have to short-circuit secondary wire of current transformer ?
The difference between current transformer and potential transformer is that the secondary of a current transformer can not be open circuited while under service whereas that of the potential transformer an be open circuited without any damage to the transformer.
How do you zero phase current transformer test
Without a load the secondary current is zero, by definition.
There are basically 4 major differences :- 1. The windings (both primary and secondary) of an ideal transformer are considered to have zero resistance, hence the transformer is lossless. 2. There is no leakage flux in an ideal transformer. 3. The permiability of the core material in ideal transformer is considered to be tending to infinity and hence the current needed to set up the flux in the transformer is negligible. 4. There is zero hysterisis and eddy current losses in an ideal transformer.
A transformer will operate with a voltage regulation of zero when it is not supplying a load.
Most likely this is referring to the initial inrush that occurs when a transformer is energized. The core of a transformer is designed for a specific magnetic field strength; When a transformer is switched into a circuit, it usually will not be switched at exactly a voltage peak. When the voltage is at its' peak, the induced magnetic field will be at zero. If the switching occurs at a voltage zero, the magnetic field strength will attempt to climb to double the designed value; since the transformer core is not generally oversized to this degree, it will saturate. This causes large inflows of current to the transformer, and shows up as even harmonics (mainly second harmonics) in the current waveform. This settles out within a few seconds (generally) to a small energizing current, usually less than 1% of the transformer's rated 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.
why does have to short-circuit secondary wire of current transformer ?
A transformer relies on AC current flowing through the primary to set up changing magnetic fields in the core. The field flows through the core and in to the secondary of the transformer, generating an AC current. The current must be AC, otherwise the magnetic field in the core of the transformer will saturate. In the same way, the armature of a dynamo or alternator must be moving in order to create a changing magnetic field to create current through the windings.
The difference between current transformer and potential transformer is that the secondary of a current transformer can not be open circuited while under service whereas that of the potential transformer an be open circuited without any damage to the transformer.
Transformer short circuit tests are used to determine the impedances (positive and zero sequence) of the transformer. A simple explanation: to do this one winding is shorted, and voltage is applied to another winding to circulate the normal full load current of the transformer. The impedance of the transformer is the applied voltage divided by the induced current. If one winding was not shorted, the voltage divided by induced current would not give the impedance of the transformer - the induced current would be much lower, giving a much higher impedance measurement that would be essentially meaningless.
A current transformer is primarily used at the neutral point of a transformer for earth fault protection. A neutral current transformer will measure any ground fault current which will essentially flow from the star point of the transformer. A fault-detection device other devices is connected to the current transformer and, if the fault current exceeds a certain trigger value, the fault-detection device will give a trip command to an earth-fault relay to disconnect the supply of electricity to the transformer.
A transformer can only increase or decrease the voltage of an alternating current, and it is called step-up transformer or step-down transformer accordingly.