Variable speed AC drive control

Claim 3

The method of claim 1, wherein in the first mode the frequency converter operates as a cycloconverter.

Claim 4

The method of claim 1 wherein, in operation of the second mode, each half-cycle of each output waveform from the frequency converter is generated by the respective resultant of a half cycle of one input phase and one or more subsequent half cycles of the same polarity from the next input phases in time.

Claim 5

The method of claim 3 wherein, in developing the said resultant, the change from one half cycle to another half cycle of the same polarity of a subsequent input phase in time occurs when the absolute magnitude of the waveform of the next half cycle is greater than that of the present half cycle.

Claim 6

The method of claim 1 wherein said AC machine has at least two phase supply terminals, said input power supply having multiple input phase terminals, said frequency converter providing a unique switchable path between each input phase terminal of said input power supply to each phase terminal of the A.C. machine.

Claim 9

The method of claim 6 wherein in the first mode the frequency converter operates as a cycloconverter.

Claim 10

The method of claim 6 wherein output includes at least two output terminals, said input power supply having multiple input phase terminals, said plurality of switching elements providing unique switchable paths between each of said multiple input phase terminals and said at least two output terminals.

Claim 11

The method of claim 6 wherein, in operation of the second mode, each half-cycle of each output waveform from the frequency converter is generated by a respective resultant of a half cycle of one input phase and one or more subsequent half cycles of the same polarity from the next input phases in time.

Claim 12

The method of claim 9 wherein, in developing the said resultant, the change from one half cycle to another half cycle of the same polarity of a subsequent input phase in time occurs when the absolute magnitude of the waveform of the next half cycle is greater than that of the present half cycle.

Claim 13

The method of claim 9 wherein the output includes at least two output terminals, said input power supply having multiple input phase terminals, said AC-AC frequency converter providing a unique switchable path between each of said multiple input phase terminals and said at least two output terminals.

Claim 14

A variable speed controller for an AC machine, comprising: a frequency converter suitable for connection to a multi-phase input power supply and for generating an output which would be provided to the AC machine, the frequency converter including power switching means, and processor means for controlling said frequency converter under control of a program residing therein to operate the frequency converter in three exclusive speed ranges within the range 0 to the frequency of the multi-phase input supply, f 1 , (i) said processor means controlling said frequency converter in a first mode within the frequency range 0 to f 0 , where f 0 is less than f 1 , to synthesize a near continuum of frequencies in the said range from said input power supply, (ii) said processor means controlling said frequency converter in a second mode to synthesize a number of output waveforms of intermediate frequency steps between the frequencies f 0 to f 1 from the multi-phase power supply, and between each frequency step further adjusting the phase of the multi-phase input power supply to obtain control over the output voltage from the frequency converter, and (iii) said processor means controlling said frequency converter in a third mode to connect the output directly to the multi-phase input power supply so that the frequency converter is effectively transparent to the multi-phase input power supply and provides an output of the the frequency converter with the input supply frequency, f 1 .

Claim 15

A variable speed controller for an AC machine, comprising: a frequency converter suitable for connection to a multi-phase input power supply and for generating an output which would be provided to the AC machine, the frequency converter including power switching means, and processor means for controlling said frequency converter under control of a program residing therein to operate the frequency converter in three exclusive speed ranges within the range 0 to the frequency of the multi-phase input supply, f 1 , (i) said processor means controlling said frequency converter in a first mode within the frequency range 0 to f 0 , where f 0 is less than f 1 , to synthesize a near continuum of frequencies in the said range from said input power supply, (ii) said processor means controlling said frequency converter in a second mode to synthesize a number of output waveforms of intermediate frequency steps between the frequencies f 0 to f 1 from the multi-phase power supply, and between each frequency step further adjusting the phase of the multi-phase input power supply to obtain control over the output voltage from the frequency converter, and (iii) said processor means controlling said frequency converter in a third mode to connect the output directly to the multi-phase input power supply so that the frequency converter is effectively transparent to the multi-phase input power supply and provides an output of the the frequency converter with the input supply frequency, f 1 .

Claim 16

The variable speed controller of claim 12 wherein said AC machine has at least two phase supply terminals, said input power supply having at least two input phase terminals, said power switching means providing a unique switchable path between each input phase terminal of said input power supply to each phase connection of the A.C. machine.