Abstract: An electric machine drive system uses an estimation of the DC bus voltage to improve machine drive control. The DC bus voltage is estimated by injecting a carrier signal into the machine drive and determining the magnitude of the positive sequence current component induced in the drive by the carrier signal. The measured magnitude of current may be referenced to the anticipated magnitude of the current in order to produce an inverse value of the estimated DC bus voltage that is then used to normalize the commanded voltage signal driving the machine. Alternatively, a look-up table is used to relate the measured magnitude of the current component to a corresponding estimated value of the bus voltage.

Abstract: A conventional full wave diode bridge of an alternator is replaced with a full wave controlled rectifier bridge having controlled switches in place of diodes and the rectifier bridge is controlled in response to a third harmonic of the voltage generated by the alternator to synchronize the rectifier bridge with the alternator and to increase output power from the alternator. The alternator includes a rotor having a field winding receiving a field current which is controlled up to a maximum field current for partial control of the output power produced by the alternator. Power produced by the alternator is also controlled by introducing a phase angle between the phase voltages at the three output connections of the stator winding and the third harmonic up to a maximum or optimum phase angle. To increase power output from the alternator, preferably the field current is increased up to a maximum before any phase angle is introduced between the phase voltages and the third harmonic.

Abstract: A conventional full wave diode bridge of an alternator is replaced with a full wave controlled rectifier bridge having controlled switches in place of diodes. Phase control is performed by the switches of the controlled rectifier bridge to preempt natural commutation and shift the phase of the alternator phase voltages relative to the phase currents. The phase angle control disrupts the normal unity power factor operation of the alternator and causes additional reactive current flow in a three phase stator winding of the alternator to source the controlled rectifier bridge. The result is that for the same operating conditions the controlled switches of the controlled rectifier bridge boost output from the alternator by from 40% to 60%.