# electrodynamic wattmeter

The field is produced by a fixed coil. This is for the purpose of making the potential-coil circuit of the meter Therefore controlling torque Tc is given as, where K = Spring constant and Ɵ = Final steady deflection, Controlling Torque Tc = Deflecting torque Td. Why PMMC Instruments cannot be used for AC Measurements?

Instead of a permanent magnet, the electrodynamometer type instrument uses the current under measurement to produce the necessary field flux. watt-hours, for each division of the dial.

Deflection is thus a function of the mean of the square of the current. A transfer-type instrument is one that may be calibrated with a dc source and then used without modification to measure AC. The field produced by the fixed coils is somewhat weaker than in other types of instruments. potential circuits may be carrying such an overload that their insulation is burning, and In principle, the watt-hour meter is a small motor whose instantaneous speed is

To reduce the effect of the stray magnetic field, the shields must be used for the instruments. 1-44.) Privacy Statement - Electrodynamometer Wattmeter consists of two coils, pressure coil (PC) and current coil (CC). The PMMC instrument cannot be used on AC currents or voltages. Q.60 Why would you use a hook-on voltameter instead of a multimeter? Where to buy cheap cable for my welding plant? Due to the moment of inertia of the moving system, the pointer will not follow the rapidly changing alternating torque and will fail to show any reading. The voltage coil is carried on a pivoted spindle which carries the pointer, the pointer moved over a calibrated scale.

The watt-hour meter is an instrument for measuring energy. google_ad_client = "ca-pub-8029680191306394"; The video below explains the working of an electrodynamometer wattmeter. For constructional detail please read. The following directions should be followed when reading the dials of a watt-hour The potential coil consists of many turns The reactance–resistance ratio of the shunt and the moving coil is kept nearly the same for the independence of the meter reading with the supply frequency. pointer depends upon the power factor of the circuit as well as upon the voltage and

google_ad_width = 728; These springs act as leads to the moving coil.

In order that the instrument should be able to read AC quantities, the magnetic field in the air gap must change along with the change in current. Spiral coil springs hold the needle to a zero position. Gravity control Spring control, only spring controlled systems are used in these types of wattmeter. Thus the current flowing in the moving coil is proportional to, and practically in phase with the supply voltage. Electrodynamic or Dynamometer Instruments In an electrodynamic instrument the operating field is produced by another fixed coil and not by permanent magnet. - A simplified electrodynamic wattmeter circuit. If, however, we were to reverse the direction of the field flux each time the current through the movable coil reverses, the torque would be produced in the same direction for both halves of the cycle. It is mounted on a shaft, carried in jeweled bearings, so that it may turn The fixed coils are made up of time. A large number of turns hence is the only option but it increases the weight of the coil. These cases are so constructed as to remain dimensionally stable over long periods of time. Since energy is the product