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Synchronous impedance curve (short-circuit characteristic curve), showing armature current as function of field current. The curve is obtained by rotating the generator at the rated RPM with the output terminals shorted and the output current going to 100% of the rated for the device (higher values are typically not tested to avoid overheating).
If the field current is increased beyond this point, the armature current becomes leading, power factor decreases, and grows again. [4] The data from the V curves can be used to set up the synchronous motor to correct the power factor of the overall system, as the power factor of the motor can be changed by simply adjusting the field current. [3]
Synchronous motors use electromagnets as the stator of the motor which create a magnetic field that rotates in time with the oscillations of the current. The rotor with permanent magnets or electromagnets turns in step with the stator field at the same rate and as a result, provides the second synchronized rotating magnet field.
In vector control, an AC induction or synchronous motor is controlled under all operating conditions like a separately excited DC motor. [21] That is, the AC motor behaves like a DC motor in which the field flux linkage and armature flux linkage created by the respective field and armature (or torque component) currents are orthogonally aligned such that, when torque is controlled, the field ...
A field coil is an electromagnet used to generate a magnetic field in an electro-magnetic machine, typically a rotating electrical machine such as a motor or generator. It consists of a coil of wire through which the field current flows.
A field coil may be connected in shunt, in series, or in compound with the armature of a DC machine (motor or generator). For a machine using field coils, as is the case in most large generators, the field must be established by a current in order for the generator to produce electricity.
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 ...
Usually applied for transients after a short circuit current. Three states are considered: [5] the steady-state is the normal operating condition with the armature magnetic flux going through the rotor; the sub-transient state (″) is the one the generator enters immediately after the fault (short circuit). In this state the armature flux is ...