mains power from car alternator 1

[colinh]

As an alternator generates AC, albeit 3 phase, can this be used to generate mains power, pref 240 V. Perhaps a transformer would be required to up the voltage.

Thanks for all help

 

[dpc]

In most cases this would not be feasible. The alternator usually has a diode bridge rectifier built in, so the output is already dc by the time it leaves the alternator. A much better solution is to purchase a small inverter that will convert the 12vdc to 120 or 240v ac. These have become quite reasonably priced in the last few years.

 

[gjones33]

Hi Colinh,

I have known of automotive alternators being re-wound for 240 volts and used as a mobile power source for welding applications.

Most alternators have 12 poles which means they produce 6 cycles per revolution. At say 1500 rpm this gives a frequency of 150 hz

Cheers,
G

 

[wvbht]

I had a ham friend that used an alternator to power his mobile transmitter. He used three high current, 12 volt filement transformers, rated at 60-400 Hz. He used to joke that the engine really slowed down when he keyed the mike.
It would not be too hard to tap onto the windings before the diode assembly to get 3 phase. This would also allow the alternator regulator to keep the winding voltages from going too high as it would still try to maintain the DC charging voltage at 13-14 volts.
He may have used the output of the primaries in a wye and then rectified that voltage and passed it through a doubler or tripler for the high tension for the final amplifier.
I cannot remember exactly what he did and he is dead and I cannot offer much else.
The DC-AC converter is the best bet, as you would be hard pressed to keep the motor at a speed to generate 60 Hz.
I hope this has given you some helpful ideas.

 

[Lewish]

Hello Colinh, In some commercial exercise equipment, there is a 3-phase permanent magnent generator. When just barely turning, it will produce 25volts and at full speed, (sorry, I don't know the exact rpm) it will produce 400volts. They are good for 500watts continuous and about 750watts for 10 to 15 seconds at a time. It might be worth looking into.
You don't say what you are trying to power (how many watts) and do you really need 3-phase?

 

[busbar]

In the US, there used to be {±1974} a moderately well-constructed aftermarket "adapter" containing not much more than a bathandled toggle switch and a duplex receptacle. When enabled, it would effectively series several of the under-hood 12-volt DC engine components and, with an engine RPM at ~2500, would furnish roughly 10 amperes at about 120VDC to the receptacle. Battery charging was absent when the receptacle was hot. [I don’t remember if things like headlights worked with the receptacle was powered.] IIRC, they were sold by traveling salesmen to contractors, with at least one later version hitting auto-parts stores.

There seemed to be fine-print warnings stating they were useable for power-tool universal motors and incandescent lighting, with an even smaller disclaimer against attempting to serve variable-speed tools and fluorescent lamps.

Then there were the “ReddiLine” AC line-voltage auxiliary sets that were driven from the fan belt—that might still be available. Their cute little DC-to-AC MG-set assemblies are listed online.

 

[mc5w]

Web site is

http://www.rediline.com

which is the company that makes the synchronous converters/dynamotors that convert 12 volts, 24 volts, or 36 volts DC to 120 volts about 45 to 70 Hertz. A dynamotor was a World War 2 technology that had a DC motor and 1 or more DC generators on the same rotor - essentially a direct current transformer. A synchronous converter was simply a DC generator with 3 slip rings connected to the commutator so that it acted as an AC to DC autotransformer. The Rediline units use seperate AC and DC windings in the same slots.

http://www,tranduction.com

has a 48 volt DC to 120 volt AC solid state inverter.

Back in the 1970s there was a product advertised in the back of Popular Mechanics or Popular Science. I think it was called an Altvolt or Altpower. Duquesne Light Company in Pittsburgh, PA installed these on nearly all of their vehicles to supply small amounts of 120 volt power. This was advertised as producing AC power. I believe that this used a high frequency 3 phase transformer that was tapped into the alternator's 3 phase power like wvbht's buddy did. The transformer stepped up to something like 150 volts AC and then used a cycloconverter (a bank of silicon controlled rectifiers) to convert down to 60 Hertz.

If you want to design and build one there are 3 things about automotive alternators:

1. The rotor has traingular pole faces to produce a trapezoidal waveform that is more suited for rectification. I have seen the patent for a DC motor that works this way - poor guy thought it up before silicon rectifiers.

2. I rebuilt the alternator for a Chevy Chevette that I had. The alternator had 14 poles. Expect surprises.

3. When rebuilding this alternator I had to clean copper oxide out of the diode bridge and put in Ilsco Deox to keep out any more oxide. The copper oxide was why the alternator was only 1/4 charging the battery.

Every time that I have hooked up an industrial machine with aluminum wire the aluminum wire was a 100% success story. The old Signal Corps method was to clean out metal oxides and sulfides with diagonal cutters or sandpaper so that all the wire strands will be conducting particularly when making a solderless connection. The Consumer Product Safety Commission version is to use Burndy Penetrox A, A13, or E in addition to cleaning the wire strands. CPSC endorses the use of #220 or #240 silicon carbide paper to get rid of aluminum oxide. If semiconductive grit will contaminate insulating surfaces I have found that #220 or #240 garnet paper works just fine. For fine stranded copper wire finer silicon carbide paper would be appropriate. Go to

http://www.inspect-ny.com

for more information.

Burndy Penetrox A and A13 have zinc particles to help bridge wire strands and conduit threads. Penetrox E has copper particles. I like to use Ideal Noalox for conduit threads and grounding of aluminum boxes even though CPSC says that it is flammable - more readily available around here. Ilsco Deox is a nongritted electrical grease that is suitable for everything EXCEPT conduit threads. Do not use Penetrox or Noalox on flat to flat connections.

Mike Cole, mc5w@earthlink.net
450 Meadowlane Road
Seven Hills, Ohio 44131

 

[hacksaw]

a lot of alternators can be simply modified to produce 120 vdc output, but it is a tricky issue given the complexity of modern automobile electricals. For example, can you imagine setting off all air bags at once....

 

[pinetar]

Shortly after WW II my dad would salvage aircraft parts, turning a bomber machine gun turret into a functioning carousel via the geared mechanism as well as selling the dynamos to a scrap yard who attached a gas engine to convert them to AC power output.

gary sz..
Strongsville, Oh

 

[mc5w]

Oh, I forgot to mention that the Altvolt or Altpower (whatever it was called) could have been a high frequency transformer plus rectifier to produced 120 volts DC. Would have been good enough to power incandescent light bulbs and single speed power tools with universal motors.

If you are dangling light bulbs into a manhole then a 120 volt power source that is independent of the one that is attached to your confined space ventilator is great. If one power source conks out.

During the August 14, 2003 blackout I used the 12 volts from my car to power some fluorescent drop lights and my shortwave radio. Next day, I had an instinct to buy some more 12 volt DC fluorescent drop lights. Sure enough, God toasted the line fuse for our street resulting in another overnight power failure.

Mike Cole, mc5w@earthlink.net