22-10-2015, 07:43 PM
(13-10-2015, 02:51 PM)Nowhere-Man Wrote: The alternator on my Lister SR2 air cooled diesel boat engine is called a "dynamo" in the service manual. It's a Lucas. ..............Hi
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The rotor (a spinning coil) is an electromagnet and works just like the old HT chokes in vintage radio that smoothed the A.C. ripple while making a magnet around the speaker. With the rotor you need slip rings and carbon brushes so the AC output can be taken to the rectifier.
Not strictly true. The winding on the rotor in an alternator is simply an electro magnet, it does not smooth the AC or DC that is generated. It is used to "regulate" the output voltage of the 3 phase alternator winding and diodes, by varying the amount of current passing through the rotor winding, this is controlled by the alternator regulator circuit, they can be either "machine sensed" or "battery sensed". A machine sensed alternator does not take into account any voltage drop in the charging circuit and cables to the battery, it in effect just regulates itself. Whereas a battery sensed alternator will have a separate wire fed back to the battery so the regulator can monitor the actual battery voltage and state of charge.
By the way, in some of the larger uninterrupted power supplies, during normal operation the AC input charges the batteries and is regulated to keep the batteries at a constant voltage. The batteries are also connected to an inverter which then powers the "uninterrupted output"
This ensures there is no interruption of power in the event of a power cut, and also the equipment is totally isolated from the mains.
They will also have a series of bypass switches so the batteries can be taken out of service for maintenance.
Mike
