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Why rated voltage is to be applied to primary for open circuit test?
Wiki User
∙ 12y ago
Open circuit test on a transformer is usually performed to measure the IRON losses.Iron losses are produced due to eddy current and hysteresis losses. In open circuit test, the LV side, generaly the secondary winding, is kept open and the HV side, generaly the primary winding is fed with the rated voltage and frequency. The rated voltage is applied in order to setup normal flux in the transformer, which in return further produces the normal iron losses at rated voltage. the wattmeter connected at the primary side will show the power consumed due to iron losses. this calculation further utilized for determing the efficiency of transformer.
Wiki User
∙ 12y ago
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What is the impedance of a transformer?
Impedance (Z) voltage is the amount of voltage applied to the primary side to produce full load current in the secondary side. It is usually listed on the transformer nameplate, expressed as a percent, and measured by conducting a short circuit test.
What will happen to the transformer if rated voltage is applied to the winding during short circuit test?
If rated voltage is applied to Transformer during S/C test, The secondary winding will burn out due ta heavy current flow through the winding. During S/C test the secondary winding is short circuited so the impedance between phase and neutral is very low(only winding resistance). But the voltage across the secondary winding is rated hence heavy current flows through the winding, as I=V/Z. it depends which rated voltage is applied. if you are talking about primary winding voltage, transformer should withstand the primary rated voltage it's been designed for (OR it has been poorly designed). Otherwise, if rated voltage is the insulation voltage between a winding and earth OR winding-to-winding, you just have to check if: 1 - it is higher than the maximum primary winding voltage the transformer can withstand (could be, could not be..). Then, you can guess if your transformer is likely to burn or not. 2 - your test setup (usually a HV generator connected between primary and secondary winding) can deliver the requested current for the setup. I guess this won't be the case, since HV testers are usually designed to generate high voltages, but very small output currents.
What is the purpose of open circuit test and short circuit test of a transformer?
An open-circuit test is done with the transformer running at its rated voltage but with no load. This measures the power lost in the magnetic core. (IR Losses) A short-circuit test is done with the transformer running at its full rated current in all windings but at a low voltage. The secondary is shorted and the primary voltage is adjusted to give the rated current. This measures the power lost in the copper windings. (Copper losses)
What is meant by rated voltage rated current and rated power of a transformer?
The ratings state the limits on voltage and current for operating the transformer at full load. The rated voltage times the rated current gives the rated VA of the transformer. Transormers are not usually rated directly for power because this depends on the power factor of the load applied.
Why do several 40watt and 220volt lamps not light to full brilliance when in series?
To get full brightness, the rated voltage has to be applied across the bulb. When several bulbs are connected in series, the voltage gets devided among these sevral bulbs and correct rated voltage will not be applied acros each bulb, hence the brightness reduces.
What is meant by rated voltage?
the voltage which is mainly applied to primary side of the transformer is called rated voltage.Answer'Rated voltage' is the nominal voltage at which an electrical device has been designed to operate.
What will happen to the transformer if the rated voltage is applied to the winding during short circuit test?
the winding would burn....
What will happen to the transformer if double the rated voltage is applied to the winding during the open circuit test?
no voltage will be induced on the secondary side of the motor as the windings will become saturated.
HOW TO CALCULATE THE IMPEDANCE FOR THE TRANSFORMER?
The term, 'percentage impedance', is a little misleading, as it is defined as 'the value of primary voltage that will cause rated current to flow in the secondary winding, expressed as a percentage of the rated primary voltage'. So, the test is carried out as follows: the secondary winding is short-circuited through an ammeter capable of reading the rated secondary current. A variable voltage is applied to the primary winding. The primary voltage is gradually increased until the ammeter indicates rated secondary current. That primary voltage is then expressed as a percentage of the rated primary voltage -and that value is the transformer's 'percentage impedance'.
Why a small percentage of voltage is applied while performing short circuit test?
short ckt test is done for the measurement of copper loss i.e the loss in windings. hence we have to give rated current. and as the primary is connected to H.V windings the vltg applied is small otherwise x'mer will get overheated.
Why do you neglect iron loss in transformer during short circuit test?
in short circuit test we apply rated current with the LV side shorted.so the applied voltage will be very low. iron loss depends on the applied voltage.so it is neglected
What is the impedance of a transformer?
Impedance (Z) voltage is the amount of voltage applied to the primary side to produce full load current in the secondary side. It is usually listed on the transformer nameplate, expressed as a percent, and measured by conducting a short circuit test.
What is rated voltage and current in transformers and how to calculate them if given 50k VA?
Rated voltage is the voltage at primary side. Rated current can be found from the equation, Rated Current= Output KVA / Output rated voltage
Why is an open circuit test performed on the low voltage side of a single phase transformer?
You always need to apply rated voltage to the primary in open circuit test (oc test helps to find iron loss which depends on the voltage applied which remains constant)so with smaller voltage applied to the low voltage side rated voltage can be achieved in primary.Further,the ammeter ,voltmeter and wattmeter connected to the primary can be of lower rating.
Why is that when an electric bulb stay just as its bright when connected to a parallel circuit?
To operate at its rated power, a lamp must be subject to its rated voltage (the supply voltage). As each branch of a parallel circuit is subject to the same voltage (the supply voltage), each lamp will operate at its rated power.
Can one intentionally short ct to one side of transformer?
yes........ we can short circuit the other side of the winding wen the primary is excited.... but we shouldn't apply rated voltage to the primary.. this method is used in the short circuit test of the transformer to find the parameters of the transformer.....
Why do light bulbs glow differently in a series circuit than in a parallel circuit?
Lamps will only operate at their rated power when subjected to their rated voltage -which is why you will see both figures shown on the glass envelope (e.g. 60 W / 230 V or 60 W / 120 V, etc.). If you connect lamps in parallel, because each branch is subject to the same voltage (i.e. the supply voltage), each lamp has the same voltage applied and will operate at its rated power. If you connect lamps in series, the supply voltage will distribute itself as a series of voltage drops where the sum of the voltage drops will equal the supply voltage. So none of the lamps is subject to its rated voltage, so none will operate at its rated power -i.e. they will be dim!
