Here we learn how to build a solar inverter circuit for a 1.5 ton air conditioner (AC) for powering the AC during daytime directly from solar panels without depending on grid power. The idea was requested by Mr. Subhashish.
Main Specifications
A 1.5 ton air conditioner is equivalent to an approximately 1.5 x 1200 = 1800 watts load which is quite huge. In order to fulfill this formidable load the solar panel spec needs to be equally robust and rated with sufficiently high voltage and current specs.
Solar panels are generally rated at lower currents compared to their voltage ratings, which in turn heavily depend on the sunlight conditions. These parameters make these devices quite inefficient with their operations and managing their power optimally becomes a challenging task for the end user.
To tackle this, sophisticated controllers such MPPT solar charge controller are designed and can be effectively implemented for acquiring the maximum from solar panels, yet still calculating a solar panel for higher loads is never an easy job for any concerned technician.
A 1.5 ton air conditioner will probably require a 2000 watt solar panel, this value will need to be ascertained with practical experimentation.
The air conditioner will be normally a 220V or 120V operated device, and therefore the panel will also need to be rated at this voltage ideally in order to produce the most efficient results without using complex controller circuits.
This can be implemented by using 60V panels in series, which means 5 such panels would need
to be connected series, with each pane rated at 2000/300 = 6.66 amps, or practically a 10amp value would be just enough.
This voltage will be a pure DC, therefore this will need to be converted to AC for operating the air conditioner.
The conversion from DC to AC can be simply done by a using a full bridge inverter circuit as shown below:
Circuit Diagram and Description
The IC IRS2453 enables the making of an efficient full bridge inverter circuit extremely easy. As can be seen the output of the IC just needs 4 N channel mosfets to be integrated for implementing a full bridge inverter actions.
The IC has a built-in oscillator, so no external oscillator stage is required for initiating the shown IRS2453 IC circuit. The Rt, Ct network associated with the IC determines the operating frequency of the inverter, and is supposed to be set at 50Hz or 60Hz depending on whether the operating voltage of the air conditioner is 220V or 120V respectively.
The IC 555 shown the left of the design is employed for generating a sine wave equivalent PWM feed for the full bridge inverter output.
The controlled PWM from the IC 555 is fed to the gates of the low side mosfets via the buffer transistor stage made through the BC547/BC557 pairs.
The above PWM feed helps the load to operate with an optimized RMS and alternating current which can be expected to be a close equivalent of the sinusoidal mains AC waveform.
The two pots associated with the IC 555 needs to be correctly adjusted until the required RMS and waveform is determined for the air conditioner.
Solar Panel Specifications
The 300V from the solar panel can be seen connected with the high side mosfet drains, which is stepped down to 15V through the indicated 33K, and 15V zener diode for providing a safe Vcc operating voltage for the two ICs.
Once the above procedures are implemented and appropriately set, the proposed 1.5 ton air conditioner can be effectively run throughout the day using only solar panels, without the need of any grid or utility power inputs.
Pls advise on 1)SOLAR AC/DC HYBRID 2HP( 18000BTU) SPLIT ROOM AIRCON
2) 100% SOLAR DC 2HP Split room AIRCON.
Can I use the solar inverter to charge 24v battery bank and run my 24v inverter from the bank and solar charger during the day. Panel is 32v 240w.
Yes, you can do that, but make sure your solar panel is sufficiently rated to charge the battery and operate the load simultaneously.
Dear Swagatam
How does the buffer transistor stage made through the BC547/BC557 pairs. work?
Is the BC547/BC557 pair on left correct? There are 2off BC547
jon
jonabadtesta@yahoo.es
Hi Jon,
When the LO1/LO2 outputs of the IC are high, the BC547 buffer BJYs conduct and supply the 15V to the gates of the low side mosfets. Simultaneously the bases of these buffer BC547 transistors are chopped by the PWM from the left side BC547 pair.
When the LO1/LO2 are low, the BC547 buffer transistors are turned off and BC557 are turned ON causing the mosfets to turn OFF. During this period the PWMs from the left side BC547 pair have no effect on the BC557 transistors.
I hope you understood the working of the transistors…yes the shown BC547 pair on the left is correct..
“I am looking for a schematic for a 5000w pure sine wave inverter. This solar inverter seems to be the closest I have been able to come. The input would be via a super capacitor bank which could be tapped into to supply the needed 15v max voltage to power the ICs.
Could you provide information on either expanding the 1800w to 5400w or stacking 3 1800w inverters to create a 5000w+ inverter. Also I intend to make up a center tap transformer to divide 220V into 2 110v circuits to provide 110 and 220v 60hz. I need a means of coming up with both 110 and 220 outlets. How few windings can I use for the transformer which will be used exclusively to provide the above voltage outputs?
Also could you clarify a few items in your schematic for me?
1, You show a number of resistors listed only as 33. At the top of the schematic you show a resistor listed at 33k, 10 watt. Should I assume the resistors listed as only 33 are 33K, 10 watt resistors?
2, What is the resistance of the resistor listed only as rt going into pin 4, Rt of the IC?
3, Am I to assume that the “load’ is the air conditioner? This may seem like a dumb question, but I have recently run into instances where a load was required to activate the system and the output was elsewhere. “
The above inverter design is unfortunately not a sine wave design. It is an adjustable RMS inverter.
To increase the power output you can add more number of mosfets in parallel with the existing ones.
You can use a secondary center tap transformer at the mosfet outputs to get both 110V and 220V.
33 at the gates of the mosfets are 33 ohms 1/4 watt resistors. When no value is mentioned it refers to ohms and 1/4 watt.
The Rt and Ct values will need to be experimented with for getting the precise 60 Hz frequency at the output.
The load can be an air conditioner or any other AC load as per the requirement.
Please sir tell us the value of rt CT by your self
Thank you
Hi Shabir, the formula can be found in the following artcile:
https://www.homemade-circuits.com/simplest-full-bridge-inverter-circuit/
remember that the Ct value will be in farads which yo will have to convert to micro farads
Hello sir,
I was going through some of your articles and this very one catches my attentions.
Assuming one has 8 units of inverter air-conditions. how would the person calculate the number of panels the mppt and inverter capacity that can power it conveniently.
I would love to see the calculation details and the circuits. Thank you in anticipation to hear you.
Thank you Comfort, the calculation is simply about using Ohm’s law, wattage of each unit multiplied by 8. The inverter must be rated at this watt with 30 to 50 % extra to handle the starting surge from the ACs.
Dear Sir,
I am very happy to hear from you.
Help me sir I am still confuse.
Please can you do an example for me using 4 units of “inverter-AC”
The Air conditions are not the normal air-conditions. They are inverter air conditions
The calculations I did seems unrealistic. Please help me. Thank you in advance.
Dear Comfort, You can refer to the following article for more details:
https://www.homemade-circuits.com/how-to-calculate-and-match-inverter/
Sir may I replace mosfet with igbt 25n120
Hi Mahendra, yes you can replace the MOSFETs with IGBTs
Hi There
Nice plce here, and beautifull projects.
However the inverter to 220 volts or 110 volts in full bridge is a class d amp in fact, you do feed right into the airconditioner motors, who does make a nice siusoidal sgnal.
However I need a sinusoidal signal allready so I need two coils and two capacitors on the full bridge outputs, I do now the cooling device here will also ste intor sinusoidal.
I have succesfully did a 3 and 5 level inverter, this does very good in terms of efficienty.
IN mine case I go full off grid, needed, two truck batteries 48 volts together and need a inverter with charge fuction for that, Reason is 48 volts is better in terms of current, less thick cables.
Do you have some formula,s to use your buck for these 48 volts 150 AH batteries?
Some of these inverters does work on grid push power in for lower bills. I think these does not be the good ones for that, need some more de design work on.
regards
Hi, thanks for liking my projects.
Yes class D amplifier is an easy and efficient way of creating pure sine wave inverters.
If you looking for a 48V battery charger, you can have a look at the following concepts and select an appropriate one for your specific need:
Simple 48V Automatic Battery Charger Circuit
HIE SWAG,
Thank you very much for such a wonderful circuit. How do you then incoorparate batteries and the charging system for the batteries. Am saying so because the airconditioning system should also work during the night.
Thank you Bernard, you can add an appropriately battery bank with the solar panel, so that it charges during the day, and could be switched to the inverter mode during night.
Hie Swag,
About connecting batteries, are there supposed to be some changes or modifications to the circuit since the output that powers the 1.5 tonne air conditioner is ac. I am a bit confused here.
Hi Bernard, the battery needs to be connected directly across the points where the panel output is connected, but the panel positive must be fed through a diode to prevent battery discharge during night
Hie Swag,
Thank you very much for the feedback.