What type of inductor should I use for single phase inverter design?

Thread Starter

Atagkh

Joined Sep 8, 2018
20
Hello,
I am designing a single phase inverter and the values of output filter is L=10mH and C=20uF. This is a big filter and should be capable of giving me a smooth output, however I see a distorted voltage in the output. My switching frequency is 10kHz and the output frequency is 50Hz. What kind of inductor should I use? I am uploading the pictures of my inductor and capacitor so that you can see their sizes because I think I might need another kind of inductor.

Regards,
Ata
 

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OBW0549

Joined Mar 2, 2015
3,022
Not much point in showing us pictures of your inductor and capacitor without also showing us a schematic diagram of your inverter circuit. How else do you expect us to help you figure out what's going wrong???
 

LesJones

Joined Jan 8, 2017
2,359
As well as the schematic (I assume you must have drawn it out on paper while designing it rather than just starting to solder components together.) showing us your calculations for the filter design would be a help. I am puzzeled by the choice of 356 hz as the resonant frequency of the filter.

Les.
 

Thread Starter

Atagkh

Joined Sep 8, 2018
20
Hello,
I have uploaded a schematic of the circuit. I want to invert 12V DC to 2V(peak-to-peak) AC. The control method is not PWM based and it is a variable frequency method. In order to determine the switching of mosfets, an algorithm is implemented in the micro-controller. So capacitor voltage and inductor current are fed back to the micro controller and then after calculations, the appropriate switching is applied to the mosfets. In order to read the inductor current, I use a 1ohm shunt resistor with high wattage, and read the voltage of each side of it and then get the current. Also in order to read three voltages shown in the schematic, with ADC, I use op-amps to decrease the voltage in the range of 0v-3v. The maximum switching frequency is 10kHz so I have decided to choose a big filter with cut-off frequency of 350Hz.
When I connect the circuit, the inductor makes a humming sound and I can see that 1Amp current is drawn from the DC voltage source. Also the output voltage is very distorted. I don't know if I need to use another kind of inductor. I appreciate the help.

Regards,
Ata
 

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Last edited:

Thread Starter

Atagkh

Joined Sep 8, 2018
20
As well as the schematic (I assume you must have drawn it out on paper while designing it rather than just starting to solder components together.) showing us your calculations for the filter design would be a help. I am puzzeled by the choice of 356 hz as the resonant frequency of the filter.

Les.
I have uploaded the schematic.
 

LesJones

Joined Jan 8, 2017
2,359
I do not understand how your inverter works just by changing the frequency without changing the duty cycle of the waveform. You will have to wait for a member with a better knowledge of inverter design to reply. I had assumed that your output filter would resonate at 50 hz but I see now it is a low pass filter.

Les.
 

Thread Starter

Atagkh

Joined Sep 8, 2018
20
Not much point in showing us pictures of your inductor and capacitor without also showing us a schematic diagram of your inverter circuit. How else do you expect us to help you figure out what's going wrong???
I have uploaded the schematic.
 
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