Electrical Machine - IES Academy
Electrical Machine - IES Academy
Electrical Machine - IES Academy
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India’s No. 1<br />
<strong>IES</strong> <strong>Academy</strong><br />
Transformer<br />
Chapter-1<br />
If the general equivalent circuit refers to the primary, the secondary quantities have been<br />
referred to the primary side. On the other hand, if the general equivalent circuit refers to the<br />
secondary, then the primary quantities must be referred to the secondary side.<br />
Open-circuit and Short-circuit Tests<br />
Open – circuit (or No Load Test): Rated voltage is applied on the low voltage side while<br />
the high voltage side is left open – circuited. All equipments are connected on the L.V. side.<br />
Only the exciting current Ie flows which is 2 – 6% of the rated full-load current. Thus, ohmic<br />
losses can be neglected. This test gives the core (constant) losses.<br />
Let the readings be POC, IOC, VOC<br />
VOC = Voltmeter reading = rated LV = V1<br />
IOC = Ammeter reading = exciting (no load) current = Ie<br />
POC = Wattmeter reading = core losses<br />
No load pf = cos θ0 = POC / V1Ie<br />
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