inductance measurement

[gupta]

i have a 2.5kva 230/115volt 50Hz transformer. i want to measure inductance of its primary and secondary windings. without an LCR meter how i can perform this task?
thanks

 

[VVV]

simple inductance measurements

You can try this, although it will not be too accurate:

Measure the input current at nominal voltage and frequency, without any load connected to the secondary. Be sure to measure the voltage, do not assume it is a certain value. From this you get:

ωLp=V/I, so Lp=(V/I)/(2*π*50) (Approximation that does not take into consideration primary resistance or losses)

Next, measure the secondary voltage with the primary at nominal voltage, again without any load in the secondary. Then the turns ratio primary to secondary is: Np/Ns=Vp/Vs
Since the inductance is proportional to the square of the number of turns, then

Lp/Ls=(Np/Ns)^2. From this you get Ls=Lp/((Np/Ns)^2)

 

[IanP]

inductance measurment

Other option is to build 2-transistor LC generator, where the winding will be the L of the L-C tank, then, having known capacitance, say, 1µF (or other), measure frequency of generated wave and calculate the inductance from the simple equasion:
L=1/C*4*Π²*f²
Choos capacitance so the frequency will be around 50-100Hz and the reading should be quite accurate ..
Good luck ..
Regards,
IanP

 

[yongchai]

IanP, your idea is interesting. What's 2-transistor LC generator? Many thanks.

 

[IanP]

Attached is an example of a simple 2-transistor LC generator that can be used to measure inductance or capacitance ..
Regards,
IanP

 

[power-twq]

1) you can use a signal generator to generate sine wave,

2) connect a series resistor to the coil under test.

3) apply sine wave signal between resistor's one end and the coil's

one end.

4) measure the voltage between coil's two end and the voltage

between resistor's two end.

5) from measured voltage, we can calculate coil's inductance.

because resistor's value is known.

best regards

i have a 2.5kva 230/115volt 50Hz transformer. i want to measure inductance of its primary and secondary windings. without an LCR meter how i can perform this task?
thanks