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I'm trying to build a Mosfet based (IRFZ44N) inverter circuit with a tubular battery as DC source.

Inverter circuit using IRS2110 Mosfet driver

Inverter circuit using IRS2110 Mosfet driver

The Inverter output was fed to the LC filter circuit and then to the 12v/220v transformer. Theoretically, as far as I know, the output must be provided with the power required by the load. But in my below case, the required load demand is not fulfilled.

Experiment : Used a 3W LED bulb across the transformer, the bulb glows but distorts the output waveform. When using 25W bulb the bulb start to fliker with the output voltage waveform across the filter as shown.

Waveform across the input of the transformer with 3W load

Waveform across the input of the transformer with 3W load

Waveform across transformer input with 25W load

Waveform across transformer input with 25W load

Waveform across transformer input with 40W load

Waveform across transformer input with 40W load

Waveform across transformer input open circuit output

Waveform across transformer input open circuit output

I'm unable to understand where am I going wrong. The signal generation is using Atmega 328P microcontroller used to drive IRS2110 mosfet driver.

The following are my questions :
1 - Why is the output power demand not met ?
2 - Do I need to implement a DC-DC converter before the inverter stage ?
3 - How to reduce distortion at the output with load ?
4 - How to stabilize the output voltage at 230V at any load ?

Edit :

Battery specs : 12V, 150Ah (Amaron) LC filter is used before the transformer. L = 100uH and C = 100uF

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    \$\begingroup\$ Provide the information about the LC filter. IMO it's the cause of the problems. \$\endgroup\$ – Marko Buršič Jan 19 '18 at 7:41
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    \$\begingroup\$ What is a tubular battery? What voltage does it produce? How much current can it deliver and at what terminal voltage? \$\endgroup\$ – Andy aka Jan 19 '18 at 9:26
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Can you see the problems of commutating a DC voltage with only 2 levels in a transformer with load ESR impedance referred to source with 400:1 Z ratio and ESR of battery?

Consider the also the reduced 3rd harmonic using a 3 level inverter using a centre tapped Tfmr with dual bridges.

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  • \$\begingroup\$ Does that mean, there is a problem of impedance matching in the current circuit? \$\endgroup\$ – Sai Prasad Jan 22 '18 at 4:14
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In order to take load, ur LC filter must satisfy the following.. Rload=(0.707)*sqrt(L/C). Thus to take load reduce the inductance and increase the capacitance and also maintain the frequency. Then connect the transformer to the capacitor without connecting the load in the secondary and make sure that your filter output does not get distored because the inductance of the primary will affect the filter.

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Try to to check with the filter alone , connecting the required resistive load across the filter capacitor.As per your circuit aprox 12 pk on both sides will come. Connect the load as per power required and check weather the voltage is stable and then move to transformer becoz transformer is just for voltage step up any ways power is going to be constant.

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  • \$\begingroup\$ I tried connecting Resistive, RL and RC load across the inverter filter. The waveform shape remains same. after the transformer waveform distorts. Tried with 2 different transformers, still the problem persists. \$\endgroup\$ – Sai Prasad Jan 22 '18 at 4:12
  • \$\begingroup\$ yes, that means your transformer is loading. If the frequency changes then your inductance of the primary winding is affecting the filter. If the amplitude across the filter drops, then increase the number of primary turns.for these kinds of stuffs you need to wind your transformer . \$\endgroup\$ – Ragavan Paramasivam Jan 31 '18 at 7:40

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