Question
Download Solution PDFA synchronous generator is feeding a zero power factor (lagging) load at rated current, the armature reaction is
Answer (Detailed Solution Below)
Detailed Solution
Download Solution PDFSynchronous generator supplying power to ZPF lagging load always operates at lagging power factor.
MMF wave diagrams of synchronous motor:
The operation of a synchronous machine may be understood by considering its m.m.f. waves.
There are three m.m.f. waves to be considered that
- Due to the field winding ϕf, which is separately excited with the direct current.
- Due to the 3-phase armature winding flux ϕa.
- Their resultant flux ϕr = ϕf ± ϕa
All the MMFs produced in the motor move at synchronous speed with respect to the stator.
Zero power factor lagging:
The armature reaction is entirely De-magnetising in nature.
ϕr = ϕf - ϕa
The net flux reduces the load to reduce the terminal voltage.
Voltage regulation is positive.
Zero power factor leading:
The armature reaction is entirely Magnetising in nature.
ϕr = ϕf + ϕa
Net flux in the airgap increased to increase induced voltage and the terminal voltage.
Voltage regulation is negative.
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