Improvements in eddy current dynamometers

Abstract

Abstract 531,787. Dynamometers. HEENAN & FROUDE, Ltd., and ROSS, E. G. Aug. 2, 1939, No. 22368. [Class 106 (ii)] A machine of the eddycurrent type employing a cylindrical rotor has arranged in its magnetic system a supplementary coil or coils excited from the variation of magnetic flux within the dynamometer. The magnetic system 1 of the machine is excited by a coil 2. The supplementary coil 3 is situated within the magnetic system and is preferably intimately wound with the coil 2. A coil 4 external to the magnetic system is in series with the coil 3 and intimately wound with a coil 5 in series with the field coil 2. The coils 4 and 5 form a mutually inductive system external tc the magnetic system of the dynamometer. Any change ir the magnetic system 1 will cause a variation of voltage in the coil 2 and a voltage is similarly generated in the coil 3 of the same sign of rate of change of variation. This causes changes in the coil 4 which induces changes in coil 5 of opposite sign and this opposes the change in the coil 2. Thus the variations in flux in the magnetic system 1 due to flux/speed conditions in the air-gap as the operational control is varied are automatically compensated for and instantaneous control of the speed and load of the machine made possible. The time effect of the coil system 4 and 5 may be fixed in some definite relationship to the systems 1, 2, 3 and this may be done by arranging a magnetic core to interlink the flux of coils 4 and 5 and this core in another form may be adjustable by means of a screw. Specification 524,080 is referred to.

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