sam khan,
Polyphase motors are inherently self-starting.
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In the case of 3-phase motors, the direction of rotation can be changed by reversing the connections to eny two phases.
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For a balanced load Wye connection, the neutral current is zero.
For a balnced load Delta connection, the circulating current is zero.
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For simple rectifier type DC power supplies the ripple is low, even with no filtering.
Regards,
Kral