Method of starting motors by harmonics and electrical motors started by this method

Claim 3

A method of starting motors according to claim 1 further including the steps of: dividing the stator winding of the motor into two parts; producing said working magnetic fields and said starting harmonics when each part of said stator winding is switched on; connecting the two parts inversely and then switching them on so that the two working magnetic fields cancel each other, but the starting harmonics strengthen each other; reconnecting the two parts normally and switching them on so that the two working magnetic fields strengthen each other, but the starting harmonics cancel each other; starting the motor at a light load; switching the first part of the stator winding on; starting the motor with the aid of the combined effect of working magnetic fields and starting harmonics; running up the motor near its rated speed; connecting the second part of the stator winding with the first part normally and switching them on so that the starting harmonics are eliminated, the working magnetic fields are strengthened and the motor is running at normal conditions; starting the motor at a heavy load; connecting the two parts of the stator winding inversely and switching them on; starting the motor by high starting torque produced by the starting harmonics; and reconnecting the two parts of the stator winding normally when the motor speed is near its rated value and switching them on so that said starting harmonics are eliminated and the motor is running normally with the aid of the working magnetic fields.

Claim 4

A method of starting motors according to claim 1 further including steps of: connecting the stator winding of the motor in Y-connection; dividing the stator winding into two parts and switching only one part of the stator winding, connected in Y-connection, on when starting; starting the motor by the starting harmonics; running up the motor to near its rated speed; and reconnecting the stator winding according to its normal conditions and switching them on so that the starting harmonics are eliminated, and the motor is running normally with the aid of the working magnetic fields.

Claim 5

A method of starting motors according to claim 1, 2 or 3 further comprising the steps of: fixingly connected a plurality of resistance elements with the rotor winding and rotating with the rotor; inducing the current in the motor by the starting harmonics produced by the stator winding to flow through said resistance elements; and inducing the current by the working magnetic fields to flow only through a part of the rotor winding and not said resistance elements.

Claim 6

A method of starting motors according to claim 1, 2 or 3, further comprising the steps of: starting the rotor using a plurality of high-resistance end-rings to serve as the resistance elements for starting, each of said end-rings having a plurality of holes, said rotor winding being a plurality of bars, the number of holes being equal to the number of bars; passing each of said bars through each of said holes and welding said bars with said end-rings; installing a plurality of connecting pieces, made of low-resistance material, on said end-rings; short-circuiting a pair of bars by each connecting piece; inducing current in said rotor bars by starting harmonics produced by the stator winding to flow through the high-resistance end-rings; and inducing current by the working magnetic fields to flow only through the bars and the connecting pieces.

Claim 7

A method of starting motors according to claim 1, 2 or 3, further comprising the steps of: connecting two points of one polyphase of the rotor winding to two slip rings; inducing current in the rotor by the starting harmonics produced by the stator winding to flow through said resistance elements; and inputting a D.C. excitation current from the slip rings to flow only through said one polyphase of the rotor winding and not said resistance elements and producing a rotor working magnetic field.