ELECTRODYNAMIC TYPE WATTMETER PDF
The wattmeter is an instrument for measuring the electric power in watts of any given circuit. Electromagnetic wattmeters are used for measurement of utility frequency and audio frequency power; other types are required for radio frequency measurements. Contents. 1 Electrodynamic; 2 Electronic. Dynamometer Type Wattmeter Principle: If two coils are connected such Hence an electrodynamic instrument, when connected as shown in. In electrodynamometer type wattmeter, moving coil works as pressure coil. We know that instantaneous torque in electrodynamic type instruments is directly.
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It consists of following parts There are two types of coils present in the electrodynamometer.
Electrodynamometer Type Wattmeter
Now the reason is very obvious of using two fixed coils instead of one, so that it can be constructed to carry considerable amount of electric current. Please share it, your one share can change my life. It consists of following parts. Did you find apk for android?
Following are the errors in the electrodynamometer type wattmeters: This mechanical force deflects the pointer which is mounted on the calibrated scale. The lowest measurable current is given as 0. Hence the current flows through the pressure coil is considered as the total load current. Please keep doing this. The torque acts on the coils electrodynnamic. Electronic wattmeters are used for direct, small power measurements or for power measurements at frequencies beyond the range of electrodynamometer-type instruments.
Before we study the internal construction of electrodynamometer wattmeterit very essential to know the principle of working of electrodynamometer type wattmeter.
Electrodynamometer Type Wattmeter
Unsourced material may be challenged and removed. Thermistors and thermocouples are used to measure heat produced by RF power and can be calibrated either directly or by comparison with a known reference source of power.
The average deflection torque is obtained by integrating the torque from 0 to T limit. Now let us derive the expressions for the controlling torque and deflecting torques.
Fixed Coil The fixed coil is divided into two equal parts and these are connected in series with the load, therefore the load current will flow through these coils. Diode detectors are either directly connected to the source, or used with a sampling system that diverts only a portion of the RF power through the detector.
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Limited of current flows through the moving coil so as to avoid heating. The scale of the wattmeter is illustrated in figure 2 in which upper scale is calibrated in milli-watts while the lower one measures the power in watts range. You must be logged in to post a comment. In electrodynamometer type wattmetermoving coil works as elevtrodynamic coil.
The strength of this field is proportional to the line current and in phase with it. The average deflection torque of the coil is given as.
The readings may be displayed on the device, retained to provide a log and calculate averages, or transmitted to other equipment for further use. Connects Facebook Youtube Videos. In other words, when the field produced by leectrodynamic current carrying moving coil F r tries to come in line with the field produced by the current carrying fixed coil F ma deflecting torque is exerted on the moving system and deflection takes place as shown in figure b.
Hence moving coil is connected across the voltage and thus the electric current flowing through this coil is always proportional to the voltage. The construction of a dynamometer instrument to some extent resembles the PMMC instrument. The deflection of the pointer is directly proportional to the power flows through it.
Dynamometer type wattmeter works on very simple principle and this principle can be stated as “when any electric current carrying conductor is placed inside a magnetic fieldit experiences a mechanical force and due this mechanical force deflection of conductor takes place”.
By limiting the current, the moving coil is made of electrorynamic weight which in turn increases the sensitivity of the instrument. The Electrodynamometer Wattmeter has two types of coils; fixed and the moving coil. Electrical and electronic measuring equipment. Moving coil moves the pointer with the help of spring control instrument.
Now let the applied value of voltage across the pressure coil be Assuming the electrical resistance of the pressure coil be very high hence we can neglect reactance with respect to its resistance. Elecfrodynamic are the advantages of electrodynamometer type wattmeters and they are written as follows: We know elechrodynamic instantaneous torque in electrodynamic type instruments is directly proportional to the product of instantaneous values of currents flowing through both the coils and the wattmeterr of change of flux linked with the circuit.
Your email address will not be published. So the expression for the torque can be written as: The two fixed coils are air-cored to avoid hysteresis effects when used on AC. Construction and Working Principle of Electrodynamometer Type Wattmeter Now let us look at constructional electordynamic of electrodynamometer. At radio frequencies a common method is a rectifier circuit arranged to respond to current in a transmission line ; the eletrodynamic is calibrated for the electrodyhamic circuit impedance.
The reduction in current required to maintain temperature is related to the incident RF power. For AC powercurrent and voltage may not be in phase, owing to the delaying effects of circuit inductance or capacitance.
Dynamometer Type Wattmeter Working Principle | Electrodynamometer | Electrical Academia
For each sample, electrodynami voltage is multiplied by the current at the same instant; the average over at least one cycle is the real power. Earlier these fixed coils are designed to carry the current of about amperes but now electrodynamkc modern wattmeter are designed to carry current of about 20 amperes in order to save power.
This page was last edited on 27 Novemberat Dynamometer type wattmeter works on very simple principle and this principle can be stated as when any current carrying conductor is placed inside a magnetic fieldit experiences a mechanical force and due to this mechanical force deflection of conductor takes place.
In practice accuracy can be improved by connecting a fixed load such as an incandescent light bulb, adding the device in standby, and using the difference in power consumption.
It uses for measuring the power of both the AC and DC circuits. Errors electrodynamoc Electrodynamometer Type Wattmeter Following are the errors in the electrodynamometer type wattmeters: