Solar Inverter for 1.5 Ton Air Conditioner

Here I have explained 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.