{TAIL ~ The engine} can be run at varying speeds causing the generator to give variable frequency AC electrical power output which is converted by the frequency converter means to an AC electrical power output having substantially {HEAD ~ the predetermined constant frequency} of the mains 
{ TAIL ~ The engine } can be run at varying speeds causing the generator to give variable frequency AC electrical power output which is converted by the frequency converter means to an AC electrical power output having substantially { HEAD ~ the predetermined constant frequency } of the mains
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