5. What is PMG in Alternators?

Answer Posted / santosh kumar verma

PMG is Permanent magnet generator mounted at the end of the alternator shaft. The alternator generally uses a self excited generator and converts its voltage to DC and then applies to Exciter armature winding through AVR. Generated voltage from this exciter fed to Main alternator field after proper rectification (Through rotary bridge rectifier) & alternator get excited, This kind of alternators are named as brushless modern alternators.
A synchronous generator whose AVR is taking its input power from the generator is termed a shunt excited generator. If the generator’s terminal voltage is reduced as is seen with transient voltage dips upon the application of significant block loading or motor starting, the input voltage to the AVR is reduced by the percentage of transient voltage dip. This reduction in input voltage to the AVR reduces its ability to force swift recovery of the generator’s terminal voltage, and may well impact the generator’s ability to start relatively large motor loads.
Meanwhile the PMG is used for stability of Alternator voltage, better regulation to make reliable source.
Please note in such system A complete brushless alternator built with the below combination
PMG + Exciter + Main Alternator

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