Open Circuit And Short Circuit Test On Transformer
Open Circuit Or No Heap Test On Transformer
Open circuit test or no heap test on a transformer is performed to decide 'no heap misfortune (center misfortune)' and 'no heap current I0'. The circuit chart for open circuit test is appeared in the figure beneath. below Open circuit
open circuit or no heap test on transformer
Generally high voltage (HV) winding is kept open and the low voltage (LV) winding is connected to its typical stock. A wattmeter (W), ammeter (An) and voltmeter (V) are connected to the LV twisting as appeared in the figure. Presently, applied voltage is gradually expanded from zero to typical appraised estimation of the LV side with the assistance of a variac. At the point when the applied voltage ranges to the evaluated estimation of the LV twisting, readings from all the three instruments are taken in circuit.
The ammeter perusing gives the no heap current I0. As I0 itself is little, the voltage drops because of this current can be dismissed.
The info power is demonstrated by the wattmeter (W). And as the opposite side of transformer is open circuited, there is no yield power. Subsequently, this information power only consists of center misfortunes and copper misfortunes. As portrayed over, no-heap current is little to the point that these copper misfortunes can be disregarded. Subsequently, presently the information power is practically equivalent profoundly misfortunes. In this way, the wattmeter perusing gives the center misfortunes of the transformer.
Once in a while, a high opposition voltmeter is connected over the HV winding. However, a voltmeter is connected, HV winding can be treated as open circuit as the current through the voltmeter is unimportantly little. This encourages in to discover voltage transformation proportion (K).
The two components of no heap current can be given as,
Iμ = I0sinφ0 and Iw = I0cosφ0.
cosφ0 (no heap power factor) = W/(V1I0). ... (W = wattmeter perusing)
From this, shunt parameters of proportional circuit parameters of equal circuit of transformer (X0 and R0) can be determined as
X0 = V1/Iμ and R0 = V1/Iw.
(These qualities are alluding to LV side of the transformer.)
Subsequently, it is seen that open circuit test gives center misfortunes of transformer and shunt parameters of the comparable circuit.
Short Circuit Or Impedance Test On Transformer
The connection graph for short circuit test or impedance test on transformer is as appeared in the figure underneath. The LV side of transformer is short circuited and wattmeter (W), voltmere (V) and ammeter (An) are connected on the HV side of the transformer. Voltage is applied to the HV side and expanded from the zero until the ammeter perusing rises to the evaluated current. Every one of the readings are taken at this appraised current.
short circuit or impedance test on transformer
The ammeter perusing gives essential likeness full burden current (Isc).
The voltage applied for full burden current is exceptionally little when contrasted with evaluated voltage. Henceforth, center misfortune because of little applied voltage can be ignored. Along these lines, the wattmeter perusing can be assumed as copper misfortune in the transformer.
Along these lines, W = Isc2Req....... (where Req is the comparable opposition of transformer)
Zeq = Vsc/Isc.
Consequently, identical reactance of transformer can be determined from the equation Zeq2 = Req2 + Xeq2.
These, values are alluded to the HV side of the transformer.
Thus, it is seen that the short circuit test gives copper misfortunes of transformer and inexact equal opposition and reactance of the transformer.
Why Transformers Are Evaluated In KVA?
From the above transformer tests, it tends to be seen that Cu loss of a transformer relies upon current, and iron misfortune relies upon voltage. Accordingly, all out transformer misfortune relies upon volt-ampere (VA). It doesn't rely upon the stage point among voltage and current, for example transformer misfortune is autonomous of burden influence factor. This is the reason that transformers are evaluated in kVA.
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