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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.
In a synchronous generator, [1] the short circuit ratio is the ratio of field current required to produce rated armature voltage at the open circuit to the field current required to produce the rated armature current at short circuit. [1] [2] This ratio can also be expressed as an inverse of the saturated [3] direct-axis synchronous reactance ...
These current and voltage values can be obtained from the open-circuit saturation curve and the synchronous impedance curve. [12] The synchronous reactance is a sum of the leakage reactance and the reactance of the armature itself (): = +. [13]
The rating of a brushless motor is the ratio of the motor's unloaded rotational speed (measured in RPM) to the peak (not RMS) voltage on the wires connected to the coils (the back EMF). For example, an unloaded motor of K v {\displaystyle K_{\text{v}}} = 5,700 rpm/V supplied with 11.1 V will run at a nominal speed of 63,270 rpm (= 5,700 rpm/V ...
This causes a demagnetizing effect due to armature reaction. [42] The V curve of a synchronous machine shows armature current as a function of field current. With increasing field current armature current at first decreases, then reaches a minimum, then increases. The minimum point is also the point at which power factor is unity. [43]
At the low values of the field current, the power factor is low, so the armature current is high (and lagging). As the field current increases, the power factor increases too, until the unity power factor is reached (the the armature current decreases to its minimum when the motor reaches this normal excitation).
What is a good current ratio? The ideal current ratio varies by industry. However, an acceptable range for the current ratio could be 1.0 to 2. Ratios in this range indicate that the company has ...
The counter-emf aids the armature resistance to limit the current through the armature. 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 and inductance.