Why cant the current from the socket turn on the air conditioner but the current in capacitor to turn it on ?
In: 1
They use induction motors, and require either 1 or 3 phase power. The phases generate a magnetic field that makes the rotor spin.
With 3 phase there’s a spinning magnetic field generated that can start from a standstill (even though it’s still hard)
With 1 phase you instead have a pulsing magnetic field, and is not rotating. The motor needs 2 phases to start itself (otheewise it could start both ways). It uses a capacitor to “cheat” a second phase into existance that can start itself (still not easy)
More precise reason from here:
The pulsing magnetic field from one phase can thought of as 2 spinning fields, a clockwise spinning one, and a counterclockwise one. The effect of the pulsing field is the same as the combined effect of the 2 spinning ones.
If the armature is spinning “with” a magnetic field it’s torque increases (to a point), so if you have a clockwise spinning rotor, then the clockwise “imaginary” field has a stronger effect than the counterclockwise, and it keep spinning that way.
With a standstill motor, both fields’ effects are the same strength, so they can’t overpower eachother. You need something to get it to spin (even you bumping it works)
The start capacitor does exactly that. It creates a second weaker phase that makes one of the directions stronger, and it starts spinning. Once it started, there’s no more need for it
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