Methods and apparatus for controlling a motor/generator

A method, comprising:

• commutating windings of a polyphase machine such that electromagnetic fields of stator and rotor phases of the polyphase machine produce at least one of motoring and generating torque;
• providing a first rotor excitation voltage having substantially no DC component when a rotational speed of the polyphase machine is below a predetermined value;
• and
• providing a second rotor excitation voltage having a DC component when the rotational speed of the polyphase machine is above the predetermined value.

An apparatus, comprising:

• a driver circuit operable to commutate windings of a polyphase machine in response to commutation control signals;
• and
• a controller operable to:
• (i) produce the commutation control signals such that electromagnetic fields of stator phases of the polyphase machine at least lead electromagnetic fields of rotor phases of the polyphase machine to produce starting torque for an engine from a battery system, (ii) command a first torque/speed profile for the polyphase machine during a first start cycle of the engine, and (iii) command a second torque/speed profile, different than the first torque/speed profile, for the polyphase machine when the first start cycle is unsuccessful.

A method comprising:

• commutating windings of a polyphase machine in response to commutation control signals;
• producing the commutation control signals such that electromagnetic fields of stator phases of the polyphase machine at least lead electromagnetic fields of rotor phases of the polyphase machine to produce starting torque for an engine from a battery system;
• commanding a first torque/speed profile for the polyphase machine during a first start cycle of the engine;
• and
• commanding a second torque/speed profile, lower than the first torque/speed profile, for the polyphase machine when the first start cycle is unsuccessful.