The iron losses of a transformer includes two types of losses,

1. Hysteresis loss and 2. Eddy current loss

V = 4.44 f Φ

Where A = area

P

The eddy current loss is given by,

P

But B

Now V

For a given volume and thickness of laminations, these losses depend on the operating frequency, maximum flux density and the voltage.

It is known that for a transformer,V = 4.44 f Φ

_{m}_{ }N = 4.44 f B_{m}_{ }A NWhere A = area

**.**B^{.}._{m}_{ }_{ }α (V/f) .......... For constant A and N Thus as voltage changes, the maximum flux density changes and both eddy current and hysteresis losses also changes. As voltage increases, the maximum flux density in the core increases and total iron loss increases.

As frequency increases, the flux density in the core decreases but as the iron loss is directly proportional to the frequency hence effect of increased frequency is to increase the iron losses.

**Key Point**: Thus iron loss increases as the voltage and frequency increases for the transformer.**Example 1**: 1 kv/ 2 KV transformer has 750 W hysteresis losses and 250 W eddy current losses. When the applied voltage is doubled and frequency id halfed, find the new losses.

**Solution**: The hysteresis loss is given by,P

_{h}α_{ }B_{m}^{1.6}_{ }fThe eddy current loss is given by,

P

_{e}α_{ }B_{m}^{2}_{ }f^{2}_{ }But B

_{m}α_{ }(V/f)**.**P^{.}._{h}α_{ }(V/f)^{1.6}x f and P_{e}α_{ }(V/f)^{2}x_{ }f^{2}**.**P^{.}._{h1 }/P_{h2 }= (V_{1}_{ }/V_{2})^{1.6}x (f_{2}_{ }/f_{1})^{1.6}x (f_{1}/f_{2}) and P_{e1}_{ }/P_{e2}_{ }= (V_{1}_{ }/V_{2})^{2}x (f_{2}_{ }/f_{1})^{2}x (f_{1}/f_{2}_{ })^{2}Now V

_{2 }= 2 V_{1 }and f_{2 }= 0.5 f_{1}**.**750/P^{.}._{h2 }= (0.5)^{1.6}x (0.5)^{1.6}x 2 and 250/P_{e2 }= (0.5)^{2}x (0.5)^{2}x (2)^{2}**.**P^{.}._{h2 }= 3446.095 W and P_{e2}_{ }= 1000 W**.**Total new iron loss = P^{.}._{h2 }+ P_{e2 }= 4446.095 W

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thx,you really helped me

ReplyDeletetransformers are rated in KVA not KW helped me in exam time thank you

ReplyDeleteReally helpful and understanable.. Thanks

ReplyDeleteThank u very much..it helps me to

ReplyDeleteunderstanding rating of T/F.

Thank you very much.. It was really helpful to me

ReplyDeleteVery clearly explained. Thank u very much!

ReplyDeleteIf frequency increased with constant voltage - hysteresis loss reduces and eddy current loss unaffected. Please correct

ReplyDeleteBut voltage is doubled here dude

Deleteiron losses depends on frequency is not correct to say , only hysteresis losses depends on frequency.

ReplyDelete