permanent magnet electricity generator

[mike50]

I had a book one time on generators and wiring used on aircraft and in it were what they called 'Motor/Generator' sets.
This was 2 sets of wiring on a single shaft, one end was the 'Motor', the other end the 'generator'.
I dont know if the windings were connected or separate but it made for a fairly compact set.
Also I cant remember now if they were only DC in and out or mixed but I doubt it was AC back then.
My idea of a 'Motor/Generator' set is either a Petrol or Diesel powered engine driving a generator/alternator to produce electricity.

Even now I have a hard time understanding why you would run an electric motor coupled to a generator to produce a different voltage but maybe when the book was written this was the most viable and practicable option available to them.

Hi Gordon

the devices you remember (as used in coms eqpt) were called "genemotors", being a motor and generator on the same physical shaft.
Used in the 1930s, 1940s and 1950s.
They were 6 or 12 or 24 volts input DC on the motor, and gave 250 or 500 volts DC at a few hundred mA output from the generator.
It is the same concept as a motor generator welder.
The input and output windings are electrically isolated.
Used to get the high voltage DC supply for vacuum tube coms eqpt (called B+ or HT).
It was the most effective and rugged method of DC - DC conversion at that time before semiconductors, to get medium levels of current capacity for the mobile or portable transmitters.
The only other DC-DC option at the time was to use a LV DC Vibrator and transformer, and these were commonly used for the lower current requirement of coms or domestic receivers.
Electrical efficiency was OK, probably of the order of 60% under load, but not great.
They were relatively heavy, and costly to produce, but reasonably reliable.
Other genemotors were made to work on aircraft 28V DC etc.

[gordon_s1942]

There is nothing wrong with experimenting and so called 'Experts' have been proven wrong time after time in many fields so keep trying with what your doing.

It was a belief in Greek times that the Human body could not withstand speeds greater than 20 KPH (12 MPH), so to travel faster than that wasnt feasible.
Radio amateurs were once restricted to a certain band because the 'Experts' believed that at that frequency, their signals 'wouldnt be able to leave their own backyards'!!!
Wrong again as experimentation led to improvements which soon had their 'Back Yard' signals circling the Globe.

You may eventually reduce the energy needed to produce energy but I can never see it being equal to or less than the output.