Normally the machine is supplied from one side of the stator winding only and the other side is isolated connected in star or delta. Open-end winding means the neutral point of the machine is opened and now the supply is possible from both side of the stator winding of the machine.
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The centrifugal switch on a motor's start winding should open at 75 to 80 percent of the motors run speed RPM.
Yes. In fact, induction motor 'starters' work using normally-open relays, controlled by low-current control circuits -although we call these heavy-duty relays 'contactors'.
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The secondary winding leakage inductance limits the current during a short. It seems that the current through the primary is limited by winding resistance and leakage resistance when the secondary is shorted.
The compressor motor employs both a start and run winding. The run winding is energized during the complete cycle of operation, whereas the start winding is energized only during the starting period. The current-operated type of relay has a coil connected in series with the run winding of the compressor. Some current-operated relays plug directly onto the compressor while others do not. Most relays are mounted in a case located on the compressor. When the thermostat closes, the compressor attempts to start, drawing heavy current through the run winding and the relay coil. This strong current flow through the relay coil creates a magnetic field strong enough to cause the start contacts to lift and close, energizing the start winding. When the compressor reaches approximately 3/4 running speed, the current flow through the relay coil decreases (due to the countering electrical magnetic field in the motor) and as the magnet weakens, the start contacts fall open. This type of relay must be used with an overload protector and must be mounted in an upright position, so that the contacts can fall freely to the "open" position.