In order to attain a desired magnetic flux density, a parallel configuration of N divided magnetic circuits is formed, and accommodated on one pair of plate cores as N groups of exciting coils. According to the configuration, the burden of the magnetic coercive force which is driven by one of the m
In order to attain a desired magnetic flux density, a parallel configuration of N divided magnetic circuits is formed, and accommodated on one pair of plate cores as N groups of exciting coils. According to the configuration, the burden of the magnetic coercive force which is driven by one of the magnetic circuits is reduced to 1/N. As a result, the consumption of the excitation power in each of the magnetic circuits can be reduced to (1/N)2. The total of magnetic fluxes which are obtained as a result of parallel driving of the N magnetic circuits are collected onto the single plate core.
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What is claimed is: 1. An electromagnetic flowmeter comprising: a plurality of magnetic pole cores which produce magnetic fluxes intersecting with a fluid to be measured flowing through a pipe; an exciting coil which applies an external magnetic field to each of the magnetic pole cores; and a pair
What is claimed is: 1. An electromagnetic flowmeter comprising: a plurality of magnetic pole cores which produce magnetic fluxes intersecting with a fluid to be measured flowing through a pipe; an exciting coil which applies an external magnetic field to each of the magnetic pole cores; and a pair of plate cores which are in contact with the pipe, wherein the electromagnetic flowmeter is of a residual magnetic field type. 2. The electromagnetic flowmeter according to claim 1, wherein each of the magnetic pole cores bear a magnetic coercive force corresponding to each of the magnetic fluxes. 3. The electromagnetic flowmeter according to claim 1, wherein each of the magnetic pole cores evenly bear a magnetic coercive force corresponding to each of the magnetic fluxes. 4. The electromagnetic flowmeter according to claim 1, wherein the plurality of magnetic pole cores are disposed on the plate cores so that all magnetic fields are aligned in a same direction. 5. The electromagnetic flowmeter according to claim 1, wherein the plate cores are disposed between the magnetic pole cores and the pipe. 6. The electromagnetic flowmeter according to claim 1, wherein the magnetic fluxes produced by the plurality of magnetic pole cores are gathered to the plate cares, the plate cares shape magnetic fluxes which evenly intersect in an interior of the pipe. 7. The electromagnetic flowmeter according to claim 1, wherein each of the plurality of magnetic pole cores forms an independent magnetic circuit. 8. The electromagnetic flowmeter according to claim 7, wherein the magnetic circuit corresponding to each magnetic pole cores has a same magnetomotive force and a same permeance, and shapes of magnetic paths are congruent with one another. 9. The electromagnetic flowmeter according to claim 1, wherein the magnetic fluxes are produced by a residual magnetic field in which a direction is alternately inverted at a constant period. 10. The electromagnetic flowmeter according to claim 1, wherein a stabilized state of a system is attained on a permeance line. 11. The electromagnetic flowmeter according to claim 1, wherein the electromagnetic flowmeter is driven by a battery. 12. The electromagnetic flowmeter according to claim 1, wherein a semi-hard magnetic material having a magnetic coercive force of approximately 400 A/m to approximately 8 kA/m is and for the magnetic pole core. 13. The electromagnetic flowmeter according to claim 12, wherein two pairs or four of to magnetic pole cores are used, and the magnetic pole cores are arranged so as to be on the same section of the pipe along a circumferential direction of the pipe. 14. The electromagnetic flowmeter according to claim 12, wherein each of the magnetic pole cores is provided with the exciting coil of the same number of turns, the exciting coils of two of the magnetic pole cores that constitute a pair are wound in a direction so as to share the same magnetic field, the exciting coils of another two of the magnetic pole cores that constitute another pair are wound in a direction so as to share the same magnetic field, and the pair of the exciting coils and the another pair of the exiting coils are opposed to each other. 15. The electromagnetic flowmeter according to claim 14, wherein the exciting coils making the pair are closely disposed on an upper face side of the pipe, and the exciting coils making the another pair are closely disposed on a lower face side of the pipe, so that the pair of the exciting coils and the another pair of the exciting coils being opposed to each other are angularly separated at a maximum degree, and the pair of the exciting coils and the another pair of the exciting coils alternately serve as a S-pole or a N-pole. 16. The electromagnetic flowmeter according to claim 14, wherein one of the plate cores is disposed between the pipe and the pair of the exciting coils so as to be in close contact with the exciting coils, another of the plate cores is disposed between the pipe and the another pair of the exciting coils so as to be in close contact with the exciting coils, and each of the plate cores has a shape extending along a circumference of the pipe. 17. The electromagnetic flowmeter according to claim 1, further comprising: electrodes disposed so as to be in contact with the fluid to be measured, wherein the exciting coils of two of the magnetic pole cores that constitute a pair are closely disposed on an upper face side of the pipe, the exciting coils of another two of the magnetic pole cores that constitute another pair are closely disposed on a lower face side of the pipe, the electrodes are opposed to each other and disposed at two places at an angle of approximately 90 degrees-with respect to an axis connecting centers of the pair of the exciting coils and the another pair of the exciting coils. 18. The electromagnetic flowmeter according to claim 17, wherein the electrodes are disposed at positions perpendicularly intersecting with a direction of the magnetic field produced by the pair of the exciting coils and the another pair of the exciting coils. 19. The electromagnetic flowmeter according to claim 1, wherein the plate cores and the exciting coils of the magnetic pole cores of both poles are placed so as to be axisymmetric about a central axis so that shapes of magnetic circuits produced by two of the exciting coils are axisymmetric and congruent.
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