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What happens when the primary winding is energized and the secondary winding is open circuited?
A voltage appears between the terminal points of the secondary winding
Why is open ckt test conducted on lv side?
in the open circuit test, the high voltage winding is open circuited and the measurements are made on the low winding side i.e, the open circuit test is performed on the L.V side. This is because if the measurements are made on HV side then voltage applied must be large and the current would be unsuitably small, for which the high voltage sources may not be readily available and at the same time the instrument ranges required should be very high, Also the result obtained may not be accurate. NOTE: iron loss will be same, if measured from either of the winding. in short circuit test. the low voltage winding is short circuited and the measurements are made on the high voltage winding side i,e,. the sort circuit test is performed on H.V side. This is because if the test is performed on the L.V side, the current will be suitably large for which the instruments used should be of very high ranges. moreover instruments of such high ranges and the auto-transformer capable of handling such high currents may not be readily available.
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 test Excitation Current of a transformer?
To test the excitation current of a transformer, you can perform an open-circuit test, where the primary winding is connected to the rated voltage while the secondary winding is left open. Measure the current flowing through the primary winding using an ammeter; this current is the excitation current. It's essential to ensure the transformer is at the specified voltage and frequency during the test for accurate results. Additionally, record the voltage and power factor for further analysis if needed.
Why high voltage is kept open in open circuit and low voltage is shorted in short circuit test?
In Short circuit test High Voltage side is feeded with 2-5% of the High Voltage rating to circulate approximately full load current in low voltage winding by short circuiting it. Low voltage is generally short circuited to facilitate measurements because it is more difficult to measure the quantities at high voltages.
What happens when the primary winding is energized and the secondary winding is open circuited?
A voltage appears between the terminal points of the secondary winding
Why is open ckt test conducted on lv side?
in the open circuit test, the high voltage winding is open circuited and the measurements are made on the low winding side i.e, the open circuit test is performed on the L.V side. This is because if the measurements are made on HV side then voltage applied must be large and the current would be unsuitably small, for which the high voltage sources may not be readily available and at the same time the instrument ranges required should be very high, Also the result obtained may not be accurate. NOTE: iron loss will be same, if measured from either of the winding. in short circuit test. the low voltage winding is short circuited and the measurements are made on the high voltage winding side i,e,. the sort circuit test is performed on H.V side. This is because if the test is performed on the L.V side, the current will be suitably large for which the instruments used should be of very high ranges. moreover instruments of such high ranges and the auto-transformer capable of handling such high currents may not be readily available.
Why keep a voltage transformer secondary open?
it is keep open so as to supply voltage to the loadAnswerThe secondary winding of a transformer is NOT necessarily kept open, unless you want to disconnect its load.
What happens when secondary of the transformer is open?
The secondary winding leakage inductance limits the current during a short. It seems that the current through the primary is limited by winding resistance and leakage resistance when the secondary is shorted.
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.
Why rated voltage is to be applied to primary for open circuit test?
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.
How to test Excitation Current of a transformer?
To test the excitation current of a transformer, you can perform an open-circuit test, where the primary winding is connected to the rated voltage while the secondary winding is left open. Measure the current flowing through the primary winding using an ammeter; this current is the excitation current. It's essential to ensure the transformer is at the specified voltage and frequency during the test for accurate results. Additionally, record the voltage and power factor for further analysis if needed.
How do you find out magnatising current of transformer?
apply 3 phase voltage(415V) to the winding whose magnetising current is to be found and open circuit another winding. now measure current using tong tester or connecting an ammeter in series between supply and winding.
What happens when a motor only has voltage no current?
Power is voltage times current. If there is no current, then there is no power. Without power, no work can be done, so the motor will do nothing.In all probability, if this is happening to a motor, then there is an open circuit someplace, perhaps an open winding.
Why high voltage is kept open in open circuit and low voltage is shorted in short circuit test?
In Short circuit test High Voltage side is feeded with 2-5% of the High Voltage rating to circulate approximately full load current in low voltage winding by short circuiting it. Low voltage is generally short circuited to facilitate measurements because it is more difficult to measure the quantities at high voltages.
What is knee point voltage of current transformer?
10 % increase in voltage gives you 50 % increase in excitation current is called knee point voltage. To measure this first demagnetise the CT and apply voltage gradually from secondary keeping primary winding open circuited. while doing this above phenomeneo will be obsesrved.
Why should current transformers be shorted off load?
If a current transformer (CT) has its secondary winding left open-circuit whilst there is current in the primary winding, the magnetic core will saturate, large eddy currents will occur in the core causing the core to heat up rapidly, the voltage in the secondary will rise to dangerously high values and the current transformer will fail catastrophically. To further describe why this happens, consider an "ideal" transformer (which has no losses at all - a reasonable assumption because transformers are generally very efficient), therefore, power in equals power out. Power can be calculated by multiplying the voltage by the current (amps using the symbol I) in each case. Therefore: Pin = Pout, or Vin x Iin = Vout x Iout, or again Vprim x Iprim = Vsec x Isec (where prim refers to the primary or input winding and sec refers to the secondary or output winding). The primary winding of current transformer is connected in series with the load, therefore the current in the primary winding is fixed by the load. Thus if the secondary winding is open circuit, the secondary current is zero, and the voltage will rise to a very high value in trying to balance this equation. It will exceed the breakdown value of the insulation and will cause an arc because the insulation will never withstand an infinite voltage! In addition to this if the secondary is open circuit, there is no magnetic flux from secondary winding current, to balance and negate any of the magnetic flux from the primary winding current as occurs in power and voltage transformers. This is the reason for magnetic saturation of the core, and the rapid heating effect of the current transformer which affects the ability of the insulation to withstand the high voltage described above. The failure of current transformers under these conditions can be explosive and highly dangerous.
