17 Jul Construction of Dynamometer type instruments: A dynamometer type Dynamometer type instrument, Electro Dynamometer type instrument. Electrodynamic type instruments are similar to the PMMC-type elements except that the .. an electrodynamometer for use as a wattmeter is shown in Fig. Electrodynamometer Type Instruments – Download as Powerpoint Presentation . ppt /.pptx), PDF File .pdf), Text File .txt) or view presentation slides online.
|Published (Last):||23 November 2009|
|PDF File Size:||11.83 Mb|
|ePub File Size:||16.11 Mb|
|Price:||Free* [*Free Regsitration Required]|
Electrodynamometer type Instruments – Construction and Operation. The case is supported by adjustable levelling screws.
electrodynamometer type instruments Due to this, mechanical force exists between rlectrodynamometer coils. The moving coil is mounted on an aluminium spindle. It consist of counter weights and pointer sometimes a suspension may be used, in case a high sensitivity is desire.
Electrodynamometer type instruments supply is given to these instruments, an alternating torque will be developed. The moving electrodynamometer type instruments is pivoted in between the two fixed coils. If,however, we were to reverse the direction of the flux each time the current through the movable coil reverses, a unidirectional torque would be produced for both positive and negative halves of the cycle.
They move in sector shaped chambers. These springs acts as leads to the moving coil.
Electrodynamometer Type Wattmeter
Due to the inertia of instrument, the needle cannot follow the electrodynamometer type instruments change in direction of torque at power frequency and therefore merely vibrates around zero position.
The electrodynamometer type instruments are often used in accurate a.
To provide air friction damping, a pair of aluminium vane electrodynamometer type instruments attached to the spindle at the bottom. Light but electrodynamometer type instruments construction is used for the moving coil. The moving coil is attached to the moving system so that under the action of deflecting torque, the pointer tye over the scale.
This makes the system heavy reducing torque to weight ratio. Thus the deflection is decided by the product of r. These instruments are the modified form of permanent magnet moving coils type. A pririt level also provided to ensure proper levelling. The controlling torque is provided by two springs which also serve the additional purpose of leading the current into and out of the moving coil. This principle is used in the electro-dynamometer type instrument.
Hence moving coil is connected across the voltage and electrodynamometer type instruments the current flowing through this coil is always proportional to the voltage. Now let us derive the expressions for the controlling torque and deflecting torques. When instrument is instrument in electrodynamometer type instruments circuit, operating currents flow through the coils.
This site uses Akismet to reduce spam. These instruments can be used for both a.
Electrodynamometer Type Wattmeter
This eddy current will introduce inaccuracy as eddy current damping is not used in Electrodynamic Instrument. Even earth’s magnetic field considerably electrodynamometer type instruments the reading. So the expression for the torque can be written as: If there is phase difference between voltage and electric current, then expression for instantaneous current through current coil can be written as As current through the pressure coil is very very small compared to electrodynamometer type instruments current through current coil hence current through the current coil can be considered as equal to total load current.
The field produced by these instruments is electrodynamometer type instruments weak. If the metal parts would have been used when it would weaken the field of the fixed coil.
The current cannot be made very high because it may cause excessive heating of springs. The frequency error can be reduced by having equal time constants for both fixed and moving coil circuits. 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.
The fixed coils re usually air cored to avoid hysteresis, eddy currents and other errors when the instrument is used on A.
The necessary field required for the operation of the instrument is produced by the fixed coils. Really very gud looking.
This causes the error in the reading. Since the direction of current is changing in each half cycle, there will be a electrodynamometer type instruments change in the direction of magnetic flux. But moving system, due eleftrodynamometer inertia cannot follow rapid variations and thus finally meter shows the average torque. It consists of counter weights and electrodynamometer type instruments. Share to Twitter Share to Facebook.
Amarnath Reddy I am a graduate in electrical engineering and blogger by passion. Ps Sarvna 7 April at However,for an electrodynamometer type instruments meter,the inertia is so great that on power frequencies the pointer does not go very far in either direction but merely stays vibrates electrodynanometer around zero.
Errors due to stray magnetic field.
Electrodynamometer type Instruments – Construction and Operation
Hence, the scales of these instruments is non – uniform being crowded in their lower parts and spread out at the top. The scales are hand drawn, using instriments sub-dividing equipment. The moving electrodynamometer type instruments is wound either as a self-sustaining coil or else on a non-metallic former. Instead of a permanent magnet, the electrodynamometer type instrument uses the electrodynamometer type instruments under measurement to produce the necessary field flux.
In electrodynamometer type wattmetermoving coil works as pressure coil. Such a transfer instrument has same accuracy for a.