selection of motor for A/C

i want to power car A/C using solar.
So the calculation of hp rating of a motor driving the compressor is cruicial.
But which type of motor would be suitable if i want to go for it?
Because if i am driving by solar then it will include the battery along with charge controller and then going for inverter and for a vfd to control ac motor doesn't sound good(due to space requirement). Would it be good if i go for dc motor?

Hi,

select by:
* HP
* RPM

If you use AC, DC or BLDC is just a problem of the control circuit.
The electrical input power is always more than the mechanical output power. There´s no way around this.


Klaus

200W should be ample. If it's a UG project, DC should be fine. But in a real world scenario, BLDC should be ideal.

You are jumping ahead of the project. Way ahead. First things first, is to determine the thermal and mechanical load.

The mechanical power (HP) requirements of a compressor depends on its thermal capacity. You have to figure out by mechanical calculation or find the data from the manufacturer.

Then and only then, you may decide on a) how much electrical power you require, and b) what type of motor and drive you are going to use.

But to answer your question, the simplest and most straightforward method would be a DC motor which is turned completely on/off by a thermostat. More complex control schemes would employ variable speed. But even then, the compressor's thermo-dynamic characteristics must be met. I am not an A/C expert, but know that a pressure differential must be met for the refrigeration cycle to operate. This pressure differential is depending on temperature differentials and motor speeds.

AC motors for compressors always have some special starting arrangements, because the motor is starting under load. For something like a fridge or deep freeze is a big negative temperature coefficient resistor to limit the inrush current as the motor comes up to speed. For air compressors there is a bypass valve that opens when the motor is stationary. So when the motor starts the compressor is only pumping against atmospheric air pressure and not the stored high pressure in the tank.
So on this basis, once you have decided on your running HP, allow for a current limited inrush of, say, five times more for 10 seconds to cover the starting period.
Frank