Various embodiments include determining an alternating current (AC) voltage and frequency of a supply voltage coupled to a circuit input. The circuit includes a soft starter circuit that is coupled between the circuit input and a first side of an AC motor. A stator winding configuration of the AC motor is determined. A control transformer is configured in response to the AC voltage and frequency, wherein the control transformer is coupled to the circuit input. A jumper device is configured on a second side of the AC motor in response to the stator winding configuration of the AC motor.

One embodiment describes a method that includes in a first switching operation of an electrical power switching system including three separately controllable single pole, single current-carrying path switching devices that provide three-phase power to a load, and control circuitry coupled to the switching devices to control closing and opening of the current-carrying paths, commanding at least one of the switching devices to open or close in advance of at least one other of the switching devices based upon a current zero-crossing or a predicted current zero-crossing of input three-phase power; and in subsequent switching operations alternating which of the three switching devices is closed or opened in advance of another of the switching devices.

An engine generator, including a general purpose engine, an engine speed of the engine being variably controlled, a generator unit having a three-phase winding and driven by the engine to generate power, an inverter unit converting AC output from the generator unit to AC of a predetermined frequency to output to a load, a connection switching unit switching a connection configuration of the winding to one of a wye-connection and a delta-connection, a load detection unit detecting a size of the load, and a connection switching control unit controlling the connection switching unit to switch the connection configuration to the wye-connection when the size of the load is equal to or lower than a predetermined value, and to switch the connection configuration to the delta-connection when the size of the load is higher than the predetermined value.

An electric motor, comprising a plurality of coils each activatable by selectively providing direct current thereto and at least one capacitor, wherein the electric motor is configured to recover energy stored in at least one of the coils into the at least one capacitor when the direct current is switched off.

An electric drive unit for driving devices connectable therewith includes at least one permanent magnets assisted reluctance motor and switching elements operatively associated to the at least one reluctance synchronous motor and designed to switch the connection of the stator windings between a first operating configuration and a second operating configuration, and vice versa, for variable torque and power delivery as a function of the rotation speed of the at least one reluctance synchronous motor.

A power tool is provided including: an electric brushless direct current (BLDC) motor having rotor and a stator defining phases; a power unit including a first switch circuit connected electrically between a first power supply and the motor, and a second switch circuit connected electrically between a second power supply and the motor; and a controller configured to control a switching operation of the first switch circuit and the second switch circuit to regulate a supply of power from at least one of the first power supply and/or the second power supply to the motor.

A power tool is provided including: an electric brushless direct current (BLDC) motor having rotor and a stator defining phases; a power unit including a first switch circuit connected electrically between a first power supply and the motor, and a second switch circuit connected electrically between a second power supply and the motor; and a controller configured to control a switching operation of the first switch circuit and the second switch circuit to regulate a supply of power from at least one of the first power supply and/or the second power supply to the motor.

A power tool is provided including: an electric brushless direct current (BLDC) motor having rotor and a stator defining phases; a power unit including a first switch circuit connected electrically between a first power supply and the motor, and a second switch circuit connected electrically between a second power supply and the motor; and a controller configured to control a switching operation of the first switch circuit and the second switch circuit to regulate a supply of power from at least one of the first power supply and/or the second power supply to the motor.

A multi-speed electric motor may include a plurality of windings arranged into winding phase groups. A speed controller may switch two or more windings between a series and a parallel configuration in each winding phase group. The speed controller may also switch the winding phase groups between a delta and a Wye configuration. By selecting a specific configuration, one or more of the holding torque, torque ratio, no-load maximum speed, and volts/Hz ratio of the AC motor may be optimized for a given application. In some embodiments, the AC motor may be used as part of a piece of drilling rig equipment such as a drawworks, winch, mud pump, top drive, or rotary table.

A power tool is provided including: an electric brushless direct current (BLDC) motor having rotor and a stator defining phases; a power unit including a first switch circuit connected electrically between a first power supply and the motor, and a second switch circuit connected electrically between a second power supply and the motor; and a controller configured to control a switching operation of the first switch circuit and the second switch circuit to regulate a supply of power from at least one of the first power supply and/or the second power supply to the motor.