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A wattmeter reads the average value of the product v(t)i(t) = p(t), where v(t) is the voltage with positive reference polarity at the ± terminal with respect to the other terminal of the potential coil, and i(t) is the current with reference direction flowing into the ± terminal of the current coil.
Each pairing of a current measuring unit plus a potential measuring unit is then termed a stator or element. Thus, for example, a meter for a four wire service will include three elements. Blondel's Theorem simplifies the work of an electrical utility worker by specifying that an N wire service will be correctly measured by a N-1 element meter.
Diagram of D'Arsonval/Weston type galvanometer. As the current flows from + terminal of the coil to − terminal, a magnetic field is generated in the coil.This field is counteracted by the permanent magnet and forces the coil to twist, moving the pointer, in relation to the field's strength caused by the flow of current.
A Rogowski coil is a toroid of wire used to measure an alternating current I(t) through a cable encircled by the toroid. The picture shows a Rogowski coil encircling a current-carrying cable. The output of the coil, v(t), is connected to a lossy integrator circuit to obtain a voltage V out (t) that is proportional to I(t).
In contrast to the parallel shunt component, the series component in the circuit diagram represents the winding losses due to the resistance of the coil windings of the transformer. Current , voltage and power are measured at the primary winding to ascertain the admittance and power-factor angle .
A wattmeter is connected to the primary side. An ammeter is connected in series with the primary winding. A voltmeter is optional since the applied voltage is the same as the voltmeter reading. Now with the help of a variac, the applied voltage is slowly increased until the ammeter gives a reading equal to the rated current of the HV side ...
Measures the frequency of the current Leakage tester: Measures leakage across the plates of a capacitor LCR meter: Measures the inductance, capacitance and resistance of a component Megger tester: Measures Resistance of an Winding of Motor or Generator And Measures Earthing's Resistance Microwave power meter: Measures power at microwave frequencies
The current through the coil magnetizes the iron, and the field of the magnetized material adds to the field produced by the wire. This is called a ferromagnetic-core or iron-core coil. [12] A ferromagnetic core can increase the magnetic field and inductance of a coil by hundreds or thousands of times over what it would be without the core.