What is an Amplidyne : Working & Its Applications

The first amplidyne was designed during the II-world war by electrical engineer namely “Ernst Alexanderson”. It is a general electric name that works as a regulated converter. During the II-world war, these devices were used for controlling guns. After the world war, they were used in large radar antennas for providing the high starting currents of the load as well as to evade overshooting and negative feedback is also given through a tacho generator. This article discusses an overview of amplidyne and its working.

What is an Amplidyne?

Definition: The most common frequent version of the Metadyne is known as amplidyne. It includes a motor & a generator where an AC motor with a constant speed can be connected mechanically to a dc generator. The amplidyne working principle is to supply large DC currents by placing heavy loads by using servo or synchro systems. At present, these are outdated technology as they replaced through power semiconductor devices like IGBTs and MOSFETs because these devices generate the o/p power in the KW range. By using this device, huge loads could be stimulated and remote-controlled. The o/p power of this can be up to several kilowatts including power amplification.

Schematic Diagram of the Amplidyne

The schematic diagram of this can be designed by changing a separately excited DC generator to amplidyne. It is a special kind of DC generator where this generator can be converted into an amplidyne.
The primary step is to short the brushes jointly so that resistance can be removed within the armature circuit. Due to extremely low resistance within this circuit, a low control-field flux can generate full-load armature current. The schematic diagram of this is shown below.

Generator Brushes Short Circuited
Generator Brushes Short Circuited

Now, the less control field needs one-volt control voltage & 1 watt of input power. The second step is to include an extra set of brushes so that it will turn into the o/p brushes for the amplidyne. These are located beside the commutator in perpendicular to the actual brushes.

Load Brushes of Amplidyne
Load Brushes of Amplidyne

The formerly shorted brushes are known as quadrature brushes because they are in quadrature to the o/p brushes. These brushes are in order through the armature flux. So, they turn off the induced voltage within the windings at this end. The o/p voltage will be the same in the generator because it generates huge output in 1000’s of watts with the i/p 100 watts.

The output generated by this device is 10,000-watt with 1-watt input only. This signifies a 10,000 of gain so that the generator gain can be increased greatly. As formerly stated, an amplidyne is mainly used for providing huge DC currents by placing huge loads through the synchro or servo systems.


Difference between Amplidyne and Metadyne

The main difference between amplidyne and metadyne are listed below.



Amplidyne is a special purpose DC generator.metadyne is a DC electrical machine including two pairs of brushes
It consists of a motor & a generatorIt includes sets of brushes
It provides huge DC currentsIt provides most of the excitation to attain high power gains
These are used in electric elevators & naval gunsThese are used for speed controlling in electric trains and control the aiming of guns.

The amplidyne characteristics are equivalent to that of a normal separately excited generator, however, its rise can be controlled through performing on the compensating winding. The winding of an amplidyne is generally designed to supply magnetizing force that is fairly larger than the demagnetizing force of the reaction of armature within the amplidyne. So overcompensate of the armature reaction is required beneath certain operating conditions of amplidyne.


The applications of amplidyne include the following.

  • These are widely used in feedback control systems
  • It can also be used as a generator to position or speed control in a Ward-Leonard system.
  • These are used for fitting of controlling overturning rolling mills, paper machines, mine hoists, cold rolling mills, and metal cutting
  • These were primarily used in electric and naval guns. After that, used to manage progressions in steelworks
  • These are used to activate the control rods in nuclear submarine designs
  • Used in Diesel-electric train engine control systems.

Thus, this is all about an overview of an amplidyne, used in high power servo & control systems in industries to strengthen small power control signals for controlling strong electric motors. But, amplidynes have a no. of shortcomings like poor commutation. So sometimes, they will disturb the operating condition of the fitting & a low efficiency of the process. Here is a question for you, what is the amplidyne transfer function?

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