Speed-changing induction motors: reduction of pole number by sinusoidal pole-amplitude modulation

Rawcliffe, G.H.; Fong, W.

doi:10.1049/pi-a.1961.0075

Cited by 11 publications

(3 citation statements)

References 2 publications

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“…Table V Further, in any design it is essential that the ac voltage across the dc terminals is made negligibly small. Since the exciting and generating windings are for different pole numbers, their mutual coupling for fundamental is zero, because ITsinPMOsinP Ode=O forPm *Pg (13) 0 However, it is essential to ensure that: (1) the exciting winding does not have a harmonic pole number corresponding to Pg, and (2) the effects of other common harmonics are suppressed by one or other winding with distribution and chording.…”

Section: Design Of Single-winding Schemesmentioning

confidence: 99%

Certain Design Aspects of Single-Winding Three-Phase Inductor Alternators

Subbiah

Krishnamurthy

1974

IEEE Trans. Aerosp. Electron. Syst.

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Based on mathematical analysis, this paper points out that restrictions in stator/rotor slot combinations for optimum output of a conventional inductor alternator are not applicable for one with a single winding for both dc excitation and output. Design considerations for the latter are discussed, and it is demonstrated that its performance is superior to a conventional double-winding inductor alternator in all aspects. Test results on a number of experimental machines fully support the theory. Symbols B = no-load air-gap flux density (Wb/m2) f = frequency of generated voltage (hertz) It= field current (amperes) K = pitch factor Kd = distribution factor I = length of the armature core (meters) 2n = coils in series per phase N = rotor speed, mechanical (rad/s) Na = turns per coil pi = rotor teeth PO = average permeance variation due to rotor slotting (Wb/m2 /At) P = half Amplitude of permeance variation due to rotor slotting (Wbhm2 /At) Pm = exciting pole number Pg = generating pole number PAM = pole amplitude modulation PSM = phase-shift modification r = stator bore radius (meters) t = time (seconds)

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Section: Design Of Single-winding Schemesmentioning

confidence: 99%

Certain Design Aspects of Single-Winding Three-Phase Inductor Alternators

Subbiah

Krishnamurthy

1974

IEEE Trans. Aerosp. Electron. Syst.

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“…Suppose that the pole amplitude n m is space-modulated for the two phase windings, respectively. Then, according to the rules, n mX = A sin kd (3) and…”

Section: Theory Of Phase-by-phase Modulationmentioning

confidence: 99%

“…The resultant of phase-by-phase modulation of 3-phase winding, as given in Reference 5, is ri\ + n 2 + n 3 Supppose that the stator is star-connected under the modulated conditions, and that the line 3 is pulled out. As a result, the effect of n 3 will vanish, and the current in phase 2 will be the reverse of that in phase 1.…”

Section: Phase-by-phase Modulationmentioning

confidence: 99%

Three-speed single-winding single-phase induction motor

Krishnamurthy

Rajaraman²

1965

Proc. Inst. Electr. Eng. UK

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SynopsisThe pole-amplitude-modulation method of obtaining economic and efficient 2-speed and 3-speed operation of a normal 3-phase squirrel-cage induction motor with a single winding, developed by Rawcliffe and Fong, has been applied to the single-phase induction motor.The paper describes the theory and design methods, and presents experimental results obtained with a 3-speed 8/6/4-pole single-phase test motor. Performance of the motor at 6 poles and 4 poles is comparable with that of normal single-phase motors, while at 8 poles it is somewhat inferior. The winding is of a perfectly standard type. Ten terminals only are required for two speeds, and 12 terminals for three speeds, the control gear therefore being extremely simple.List of principal symbols n = magnetising turns, due to a phase winding acting at an angular position 6, measured mechanically around the perimeter n m = magnetising turns acting at the centre of each pole p = pole pairs k = modulation cycles in the complete machine perimeter k w = winding factor X = pole pitch x = slot pitch N = turns in seriesThe suffixes 1 and 2 refer to the 2-phase windings. A is used as a constant and also in referring to phase A, as explained in the text. Similarly, B is used for flux density and also in referring to phase B.

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