Electrical Engineering ⇒ Topic : Range of vibrating Reed frequency meter
Range. The usual range of such frequency meters is 6 Hz say from 47 Hz to 53 Hz. They maybe used in electric power system where the maximum variation of frequency is only a few cycles. The frequency range of this meter may be doubled by polarising the electromagnet i.e., by using a d.c. winding on the electromagnet in addition to the a.c. winding. The magnitude of direct current through the d.c. winding is so adjusted that steady flux produced by it is equal in magnitude to the alternating flux of the a.c. winding.
Let us illustrate polarisation of the electromagnet with a numerical example. Suppose the frequency to be measured has a value of 50 Hz. If the electromagnet is unpolarised (i. e . , only a.c. winding is excited), then the reed whose natural frequency is 100 Hz will respond the most. On the other hand, if the electromagnet is polarised (i. e . , both a.c. and d.c. windings are excited), then the reed whose natural frequency is 50 Hz will respond the mos
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