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Industrial Electric Motors and Generators Menu
Synchronous Motor Supplier
For a constant load, the power factor of a synchronous motor can be varied from a leading value to a lagging value by adjusting the DC field excitation (Figure 1). Field excitation can be adjusted so that PF = 1 (Figure 1a). With a constant load on the motor, when the field excitation is increased, the counter EMF (VG) increases. The result is a change in phase between stator current (I) and terminal voltage (Vt), so that the motor operates at a leading power factor (Figure 1b). Vp in Figure 9 is the voltage drop in the stator winding’s due to the impedance of the windings and is 90o out of phase with the stator current. If we reduce field excitation, the motor will operate at a lagging power factor (Figure 1c). Note that torque angle, a, also varies as field excitation is adjusted to change power factor.
Synchronous motors are used to accommodate large loads and to improve the power factor of transformers in large industrial complexes.
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