What is Metadyne : Working and Its Applications

The metadyne was known for several years because it is a DC generator. These generators were described by Gravier in the year 1882, Rosenburg in the year 1904, and Osnus was discussed the no. of feasible arrangements in the year 1907. The theory of such devices was developed by Pestarini in between 1922-1930 and proposed a name like Metadyne for the general type of machines. These machines are attained by arranging extra brushes to normal generators. The fist metadyne device was used in the control system of electric trains by the company of metropolitan Vickers in the Britain country.

What is a Metadyne?

Definition: An electric DC machine that has two pairs of brushes is known as metadyne. This dc machine is used as a rotating transformer or an amplifier. It is related to a third brush dynamo although includes extra windings of varistor otherwise regulator. Metadyne characteristics are equal to an amplidyne except a compensate winding in the latter which completely offsets the result of the generated flux through the load current. The technical explanation is “a cross-field dc machine mainly designed to use armature reaction”. The main function of a metadyne is to change the input of stable voltage into a stable current and uneven voltage output.

Metadyne Working Principle

The constant current device like metadyne is mainly designed to use armature reaction. The working principle of metadyne is to change the i/p of constant voltage to current and variable o/p voltage. The schematic diagram of the metadyne is shown below.

Metadyne Construction
Metadyne Construction

The arrangement of the metadyne control system mainly includes three arrangements which are shown in the figure. In the first arrangement, it signifies a cross-field machine that includes a single cycle. In a DC machine, the excitation current effect will generate a flux represented with A1, and at right angles to the exciting flux, it generates a quadrature flux. By connecting the quadrature brushes mutually, the current can be generated within the armature. The A2 flux generates at right angles in the direction of the quadrature axis and gives an armature reaction. This armature reaction is directly proportional to the actual excitation.

This characteristic is basic to the machine and it does not lie in its rotation direction. Once the armature reaction is incompletely compensated through a compensation winding, and then the uncompensated part of the armature reaction works in this way. When the o/p current increases, it restrains the excitation effect, until it achieves a state where there is sufficient excitation to continue the current. If any current increases, the flux can be eliminated which maintains its operation and the back emf can be generated through it. Thus, this machine works like a constant-current generator, wherever the current is relative to the excitation.

In the second diagram, a machine includes no excitation windings, but in its place, a stable voltage can be given to the quadrature brushes. This generates a flux similar to the one generated through the armature rotation within the excitation flux. The machine operation is extremely similar to the increasing o/p current until the flux generated through the applied voltage. The metadyne generator can be partly compensated with the Metadyne transformer and operates continually like a stable current device until the compensation increases are maximum.


In the third diagram, a metadyne is connected to 2 separate motors. This connection was frequently used to control the traction motors within electric trains. Once the metadyne is connected, it will reduce the effective loading & allows a small machine to be fixed. The Metadyne works like a booster. Even though the system is horizontal to the currents within the two divides of the load that becomes unbalanced. The unbalanced load can be modified through the condition of additional series windings, which work as an extra circuit resistance.


The applications of metadynes include the following.

  • These are used to control large guns & controlling the speed of electric trains.
  • It can be used as a rotary transformer/an amplifier.


1). What is metadyne?

It is like a dc electric machine used as a rotary transformer.

2). What is the function of metadyne?

It is used to control the speed of electric trains and control the aiming of guns.

3). What is amplidyne?

It is a special purpose dc generator, used to supply dc current and controls heavy loads like missile launchers

4). How does amplidyne work?

It includes an electric motor that activates a generator on a similar shaft. Different from motor and generator, it is not to produce a stable voltage however to produce a voltage that is proportional to an i/p current to strengthen the input.

Thus, this is all about an overview of Metadyne and its working. It is a DC electrical machine that includes two sets of brushes. These are used as a rotary transformer otherwise an amplifier. Here is a question for you, what is amplidyne?

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