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Armature reaction is essential in amplidyne rotating amplifiers. Armature reaction drop is the effect of a magnetic field on the distribution of the flux under main poles of a generator. [5] Since an armature is wound with coils of wire, a magnetic field is set up in the armature whenever a current flows in the coils.
When both the armature and the field windings are excited by a DC supply, current flows through the windings and a magnetic flux proportional to the current is produced. When the flux from the field interacts with the flux from the armature, it results in motion of the rotor. Armature control is the most common control technique for DC motors.
where is the armature current of the machine (SI unit: ampere). is primarily used to calculate the armature current for a given torque demand: = The SI units for the torque constant are newton meters per ampere (N·m/A).
A growler consists of a coil of wire wrapped around an iron core and connected to a source of alternating current. When placed on the armature or stator core of a motor the growler acts as the primary of a transformer and the armature coils act as the secondary. A "feeler", a thin strip of steel (hacksaw blade) can be used as the short detector.
In synchronous machines, the V curve (also spelled as V-curve) is the graph showing the relation of armature current as a function of field current in synchronous motors keeping the load constant. The name comes from an observation made by W. M. Mordey in 1893 that the curve resembles a letter V. [1]
When the armature reaction is partially compensated by a compensation winding, the uncompensated portion of the armature reaction acts in this way. [11] As the output current rises, it suppresses the effect of the excitation, until it reaches a state where there is just enough excitation to maintain the current.
When power is first applied to a motor, the armature does not rotate. At that instant, the counter-EMF is zero and the only factor limiting the armature current is the armature resistance. Usually the armature resistance of a motor is low; therefore the current through the armature would be very large when the power is applied.
A compensation winding in a DC shunt motor is a winding in the field pole face plate that carries armature current to reduce stator field distortion.Its purpose is to reduce brush arcing and erosion in DC motors that are operated with weak fields, variable heavy loads or reversing operation such as steel-mill motors.