Thanks everyone for their help.
So as I now understand it: If the load is increased and nothing is done the voltage in the system will drop. In the voltage regulator a feedback circuit detects this drop and increases the current to the electromagnet thereby increasing the strength of the magnetic field and returning the voltage to a preset value. The RPM cannot be changed as this would affect the frequency.
So if output voltage is only governed by the RPM and magnetic field strength and RPM remains constant, it must therefore be the addition of load that is decreasing the output voltage making an increase in magnetic field strength necessary. Is this correct?
Kind regards,
MHA
P.S. Lancelot hope you enjoying the W.A. weather, does get a little boring after a while though!