Sine wave shape distorts when transformer is connected.

rocon123

Joined Jun 26, 2015
27
Distortion on a current waveform is normal, there are a number of potential sources.
The B/H curve of the iron core is not linear and there can be localised areas of saturation which you can only discover by modelling the magnetic circuit. Kermit2 has pointed out the phase shift issue. The meter, which loads the circuit will have an electronics board with a bridge and a capacitor which also distort the current waveform. I think what you are seeing is normal and not much can be done.

What is your problem? are you testing meters and worried about accuracy?

Peter
peter,
I need to worry because if i will connect load at output of meter which expects pure sine wave, this distorted wave can damage that load.
My ultimate aim is to boost sinusoidal current waveform from 0.5A to 10A. 0.5A is maximum current i can pass in inverter board.
help.

rocon123

Joined Jun 26, 2015
27
There are magnetic fields in your load which must alternate polarity. Current and voltage waves are phase shifted in transformers. Inductors "resist" any change in current flow. Those three things combined can cause what you see on the scope.
The current flow reverses in the primary BEFORE the magnetic field can follow it. The result is a back EMF created by the inductor which counters the input voltage as it crosses zero
Can you suggest any solution to overcome this issue?

PeterCoxSmith

Joined Feb 23, 2015
148
peter,
I need to worry because if i will connect load at output of meter which expects pure sine wave, this distorted wave can damage that load.
My ultimate aim is to boost sinusoidal current waveform from 0.5A to 10A. 0.5A is maximum current i can pass in inverter board.
help.
It is the voltage waveform that drives the load and the current waveform is a consequence of the type of load. You only need to make sure you are not distorting the voltage waveform. Put a resistive load on the secondary and plot the secondary waveform.

rocon123

Joined Jun 26, 2015
27
but when i connect that transformer, both secondary current abd voltage waveform distorts. after all voltage shape will be same as current. are you telling that it is due to meter, which i am using as load now?
It is the voltage waveform that drives the load and the current waveform is a consequence of the type of load. You only need to make sure you are not distorting the voltage waveform. Put a resistive load on the secondary and plot the secondary waveform.
but when i connect that transformer, both secondary current abd voltage waveform distorts. after all voltage shape will be same as current. are you telling that it is due to meter, which i am using as load now?

PeterCoxSmith

Joined Feb 23, 2015
148
but when i connect that transformer, both secondary current abd voltage waveform distorts. after all voltage shape will be same as current. are you telling that it is due to meter, which i am using as load now?
...using a meter applies a short circuit as the load. Your inverter and transformer are unlikely to be able to supply a short circuit. Remove the meter, measure the open circuit voltage on the secondary, calculate and fit the resistive load that will draw full current rated at the necessary power. Fit the meter in series with the resistor in the secondary circuit. Check and record the voltage waveforms from the inverter terminals, at the transformer primary terminals and the resistive load terminals (!! and don't short them all together with your scope earth connection!!). Put them on the Blog and let's see the whole picture.