A power tool having an electronically commutated DC motor capable of providing various operating modes ranging from a maximum efficiency operating mode to a maximum power operating mode. The motor has a rotor having permanent magnets mounted in recesses in a back iron of the rotor. In one embodiment the motor has three phase windings, each having at least a pair of coils. The phase windings are connected in either a delta or a wye configuration via electromechanical or electronic switching components, or a combination of both, by a controller within the tool. The coils in each phase winding can also be switched between series and parallel configurations to configure the motor to provide its various operating modes. In one embodiment a dual wound motor is disclosed that has its phase coils dynamically or statically switchable between series and parallel configurations.