EE361-Electromechanical Energy Conversion

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# EE-361
# TRANSFORMER TESTS
## Open-Circuit, Short-Circuit Tests

## Ozan Keysan

[keysan.me](http://keysan.me)

Office: C-113 <span class="meta">•</span> Tel: 210 7586

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## How to Test a Closed System?
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<img src="https://www.kroger.com/product/images/large/back/0000000004031" alt="Drawing" style="width: 600px;"/>
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### [Impact Test Siemens](https://youtu.be/UfiabSc8w-U?t=118), [Modal Analysis](https://www.youtube.com/watch?v=Fn9xPMsrrBs)

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# How to Test a Linear Circuit?
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## Open-Short Circuit Test for Thevenin-Norton Circuits
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# Procedure for Transformers
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- # Open Circuit (No-Load) Test
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- # Short Circuit Test

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# Open Circuit Test
## Secondary Side Open-Circuited (No Load)
<img src="http://upload.wikimedia.org/wikipedia/commons/d/d8/Open_circuit_test.png" alt="Drawing" style="width: 900px;"/>

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# Open Circuit Equivalent Circuit
![](http://upload.wikimedia.org/wikipedia/commons/thumb/1/10/Transformer_equivalent_circuit-2.svg/786px-Transformer_equivalent_circuit-2.svg.png)

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# Simplified (Approximate) Equivalent Circuit
## Open Circuit Test

### Almost no current on the series branch

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# Simplified (Approximate) Equivalent Circuit
## Open Circuit Test

### Almost no current on the series branch

### Power dissipates on Rc, total current is determined by equivalent impedance (Rc // Xm)

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# Short Circuit Test

### In short-circuit test, secondary side is shorted (but be careful)

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# Short Circuit Test

### In short-circuit test applied voltage is much smaller than the rated voltage.
### \$V\_1 \ll V\_{rated} \$

[What happens if you apply rated voltage at short-circuit?](https://www.youtube.com/watch?v=D8EQPx-ptKk)

[Trafo Kısa Devre](https://www.youtube.com/watch?v=_Qh822feKZo), [Not a transformer but a phase-phase short circuit](https://www.youtube.com/watch?v=_rm2KQpGu-8)
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# Short Circuit Equivalent Circuit
### Neglect Parallel Branch! 
#### Current in the parallel branch is negligible due to small input voltage.

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# Short Circuit Equivalent Circuit
### Neglect Parallel Branch!

#### Power dissipates in series resistance (\$R\_{eq}\$), current is determined by equivalent impedance (\$R\_{eq} + j X\_{eq}\$)

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#### Series impedances can be calculated

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# Example

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# Example
## A 1000 VA, 230/115 V transformer has been tested from its primary winding:
## Find the equivalent circuit parameters.
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## No-load Test:

### $$V_o = 230 V \quad I_o = 0.45 A \quad P_o = 30 W $$

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#Example
## 1000 VA, 230/115 V transformer has been tested from its primary winding:
## Find the equivalent circuit parameters.

## Short Circuit Test:

### $$V_s = 13.2 V \quad I_s = 6 A \quad P_s = 20.1 W $$

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#Example

## Answers:
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### $$R_c = 1763 \Omega $$
### $$jX_m = j 534 \Omega $$
### $$R\_{eq} = R\_{1} + R\_{2}^{'} = 0.558 \Omega $$
### $$jX\_{eq} = jX\_{1} + jX\_{2}^{'} = j2.13 \Omega $$

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# Electrical Safety
## You're just a resistor!

### Some incidents (warning: may be disturbing)
### [20kA Arc](http://www.youtube.com/watch?v=hA-w0QAaxRU), [Arc Flash](http://www.youtube.com/watch?v=dPJtknGmsys), [Overhead line electructed workers](https://www.youtube.com/watch?v=gFk1wh96abg)

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# Electrical Safety

- ## Cut-off electricity

- ## Protect Yourself

- ## First Aid (Seconds count)

- ##Call for help

### [Safety video](http://www.youtube.com/watch?v=6rZcQTbOfLM), [Safety video2](http://www.youtube.com/watch?v=wal2KP1bbIY), [Safety video3](http://www.youtube.com/watch?v=WNot2owIv8c)

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## You can download this presentation from: [keysan.me/ee361](http://keysan.me/ee361)