A circuit includes phase windings, a power switch circuit comprising at least one power switch at a midpoint of the phase windings, a direct current (DC) supply circuit at the midpoint of the phase windings, and one or more non-collapsing DC power supply components to prevent the DC power supply from collapsing when the at least one power switch is on and conducting during one or more portions of a cycle. The one or more non-collapsing DC power supply components each may include one or more of a tap from one of the phase windings electrically connected to the DC power supply, a secondary phase coil winding connected to the DC power supply to power the power supply, one or more resistors between the one of the phase windings and the power switch circuit, one or more Zener diodes between one of the phase windings and the power switch circuit, and/or an electrical component to create a voltage drop between one of the phase windings and the power switch circuit to prevent the power supply from collapsing when the at least one power switch in the power switch circuit is on and conducting.

A circuit includes phase windings, a power switch circuit comprising at least one power switch at a midpoint of the phase windings, a direct current (DC) supply circuit at the midpoint of the phase windings, and one or more non-collapsing DC power supply components to prevent the DC power supply from collapsing when the at least one power switch is on and conducting during one or more portions of a cycle. The one or more non-collapsing DC power supply components each may include one or more of a tap from one of the phase windings electrically connected to the DC power supply, a secondary phase coil winding connected to the DC power supply to power the power supply, one or more resistors between the one of the phase windings and the power switch circuit, one or more Zener diodes between one of the phase windings and the power switch circuit, and/or an electrical component to create a voltage drop between one of the phase windings and the power switch circuit to prevent the power supply from collapsing when the at least one power switch in the power switch circuit is on and conducting.

A circuit includes phase windings to receive alternating current (AC) line voltage. The circuit has a direct current (DC) power supply, a power switch circuit comprising at least one power switch, and a control circuit to turn off the power switch circuit when a rotor associated with the circuit is in an identified rotor position, rotor magnet polarity, or speed relative to the AC line voltage. The circuit also has at least one non-collapsing DC power supply component to prevent the DC power supply from collapsing when the at least one power switch is on and conducting during at least a portion of a cycle. One or more of the DC power supply, power switch circuit, and control circuit may be at a midpoint of the phase windings.

A circuit includes phase windings to receive alternating current (AC) line voltage. The circuit has a direct current (DC) power supply, a power switch circuit comprising at least one power switch, and a control circuit to turn off the power switch circuit when a rotor associated with the circuit is in an identified rotor position, rotor magnet polarity, or speed relative to the AC line voltage. The circuit also has at least one non-collapsing DC power supply component to prevent the DC power supply from collapsing when the at least one power switch is on and conducting during at least a portion of a cycle. One or more of the DC power supply, power switch circuit, and control circuit may be at a midpoint of the phase windings.

A motor drive controller includes: a control circuit unit configured to output a drive control signal for driving a motor in response to a command signal externally input to the control circuit unit; and a motor driving unit configured to output a drive signal to the motor based on the drive control signal output from the control circuit unit. The control circuit unit is provided with: a speed setting unit configured to generate a target rotation speed signal corresponding to a target rotation speed based on a command step determined in response to a step command signal and predetermined setting information when the step command signal is input as the command signal; and a drive control signal generating unit configured to generate and output the drive control signal based on the target rotation speed signal.

A method for synchronizing a high inertial load with a line-start synchronous motor involves providing a rotor core with rotor bars being formed of a highly conductive material. In accordance with one aspect of the method, a user is directed to operatively couple a load to the motor and drive the load from start to at least near synchronous speed during steady state operation of the motor with the load coupled thereto. The load has an inertia that is greater than an inertia associated with a load driven by a like motor subjected to an equivalent range of starting current but having rotor bars formed from a conductive material having a conductivity lower than that the highly conductive material.

A method for synchronizing a high inertial load with a line-start synchronous motor involves providing a rotor core with rotor bars being formed of a highly conductive material. In accordance with one aspect of the method, a user is directed to operatively couple a load to the motor and drive the load from start to at least near synchronous speed during steady state operation of the motor with the load coupled thereto. The load has an inertia that is greater than an inertia associated with a load driven by a like motor subjected to an equivalent range of starting current but having rotor bars formed from a conductive material having a conductivity lower than that the highly conductive material.