No , voltage will increase with speed . The idea is to control the voltage by varying the strength of the magnetic field . The field is , most of it , produced by the current in the field windings which surround the iron pole pieces . So you can vary the strength of the field by varying the current through the field windings .
All the regulators work this way . The old CVC boxes have a make and break mechanism operated by an electromagnet taking the dynamo voltage . This operates against a spring to break the field circuit at a set voltage . The voltage then drops , and the circuit is reconnected by the spring . This sequence is then repeated , in the same way that a bell buzzer works . Otherwise one could have a variable resistance in the field circuit which could be operated manually .
The whole idea is that it is easier to control the voltage by controlling the small current through the field windings than to put a heavy resistance in the main circuit .
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