OC and SC test on Transformers PDF

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Application and variety of transformers...

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FR. CONCEICAO RODRIGUES COLLEGE OF ENGINEERING Department of Electronics Engineering 6. OC and SC tests on Transformer 1. Course, Subject and Experiment Details Student’s Name

Roll No.

Academic Year Subject Name and Code

2017 - 18 Basic Electrical Engineering (FEC 105)

Date Course and Semester

FE All Semester I

2. AIM : To determine the efficiency and regulation of a single phase transformer by perfor ming the OC and SC tests.

3. EXPECTED OUTCOME OF THE EXPERIMENT This exper iment helps students in understanding the need of testing a transformer and how to conduct transformer tests without wasting energy.

4. APPARATUS: 1. Auto transformer 2. Voltmeter 3. Ammeter 4. Wattmeter 5. Transformer 6. Connecting wires

230 V/0-270 V, 50 Hz. 0-300 V MI 0-75 V MI 0-1 A MI 0-10 A MI 1A, 300 V 5A, 50 V 1 KVA, 230/110 V, 50 Hz

1 No. 1 No. 1 No. 1 No. 1 No. 1 No. 1 No. 1 No.

5. PRINCIPLE : The efficiency, regulation and other parameters of a transformer ca n be deter mined b y conducting two tests namely open circuit (OC) and short circuit (SC) tests.

Open Circuit Test Under no load, the current taken by the transformer is very low. So copper loss can be neglected. Then the power taken by the transformer (Woc)= Iorn loss (W i) From the no load vector diagram, W oc = Voc Ioc Cos Φ 0 Cos Φ0 = Woc/Voc Ioc Iw = Ioc Cos Φ 0 = Im Ioc Sin Φ 0 Ro = Voc/Iw ; Xo = Voc/Im

Short Circuit Test Under short circuited condition, the volta ge that is to be app lied to make rated current to flow through the transformer is very low. So iron loss can be neglected. Then the power taken by the transformer (W sc) = Copper loss (W c) Z02 = Vsc/ Isc 2 = (Z - R ) ; X 2 1/2 2 R02 = W sc/Isc 02 02 02 (If SC test is conducted on secondary of the transformer)

Total voltage drop w.r.t. secondary VDO2 = x.I2.(R02 Cos Φ ± X02 Sin Φ) By knowing the voltage drop, the % regulation can be calculated by using the formula : % regn and

Efficiency,

= VDO2 × 100 E2 η = input - losses input

6. PROCEDURE : Open Circuit Test 1. 2. 3. 4.

Make the connection as shown in diagram No.1 Adjust the supply voltage to the rated value lv side. Note the meter readings and tabulate. Calculate the iron loss and no load parameters

Short Circuit Test 1. 2. 3. 4. 5. 6.

Make the connection as shown in diagram No.2 Short circuit the lv side of the transformer. Keep the auto transformer at minimum position Adjust the auto transformer voltage until rated current flow through hv side. Note the meter readings and tabulate. Calculate the copper loss and other transformer parameters 7. Calculate the efficiency and regulation at F.L, 0.8 pf lagging 8. Draw the equivalent circuit w.r t. primary...