Alexandre, please keep in mind that motors are big inductors that appear
almost as dead shorts when turned on. Unlike real big inductors. And the
kind of motor that is used in air conditioner compressors definitely
refuses to start if not supplied enough current. Plan for about as much
starting current as I = 1.5 * Uac / Rin, where Uac is your ac mains
voltage and Rin is the resistance you measure at the motor terminals with
the motor off. Multiply the result by 2 if the motor has a solenoid type
starter (because it does not appear in the circuit when measuring ohms).
If you get to do this and rub your eyes, and check the meter, it's ok for
a 2kW motor to show 2 to 10 ohms Rdc ;-), and sometimes less.  50 or 100A
start current is not uncommon for a motor that normally draws 10A. There
is a good reason for virtually all airconditioner makers using a relay to
switch the load in despite of fancy electronics.

Peter

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