# Single phase transformer lab help

#### Bibbster

Joined Mar 28, 2013
9
Hi guys, currently doing a lab just now for a single phase transformer. i'm getting along fine with it however there is one question holding me back and it is as follows:

Compare and comment on the measured transformer secondary voltage considering the rating of the transformer.(i'll put details of transformer etc at bottom)

Now this is in the open circuit test section bit of the lab....

Transformer
1.Rating= 750 VA
2.Frequency = 50 Hz

Test: 10 11 12 13
Primary Voltage: 180 200 220 230
secondary voltage:54 60 66 68
Turn Ratio: 3.3 3.3 3.3 3.82

#### #12

Joined Nov 30, 2010
18,224
There is only one number that is not the obvious answer. Why is that one number out of place?

(Don't tell me, tell the teacher.)

#### Bibbster

Joined Mar 28, 2013
9
There is only one number that is not the obvious answer. Why is that one number out of place?

(Don't tell me, tell the teacher.)
i assume you mean the 3.82 for the turns ratio?

#### t_n_k

Joined Mar 6, 2009
5,455
One normally measures other parameters in a transformer test. What else did you measure on the open circuit case?

#### Bibbster

Joined Mar 28, 2013
9
One normally measures other parameters in a transformer test. What else did you measure on the open circuit case?
We had to calculate rm and xm values, we also measured primary and secondary voltage values + primary current values...

#### t_n_k

Joined Mar 6, 2009
5,455
For the open circuit test, was there any indication in the corresponding primary current values that might be related to the observed primary:secondary voltage ratio "anomaly" at the upper primary voltage?

#### Bibbster

Joined Mar 28, 2013
9
For the open circuit test, was there any indication in the corresponding primary current values that might be related to the observed primary:secondary voltage ratio "anomaly" at the upper primary voltage?
No there wasn't..

#### t_n_k

Joined Mar 6, 2009
5,455
In the absence of any related changes in other parameters, one might conclude you have made a measurement error for that particular observation?

My "remote possibility" thought was that you might have been running into saturation issues which would seem curious if the transformer is rated for 230V input. In any event such a rapid change in behavior seems doubtful over a relatively small change in input voltage.