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Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment.

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Old 21st May 2012, 10:56 am   #1
M0FYA Andy
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Default Inverter Type 200

Perhaps a long-shot, but does anyone have any information on this aircraft rotary inverter and associated control unit, please?
I don't know what it was designed to power, probably not comms equipment, I suspect more likely something like Gee or IFF equipment.
28v DC input, 115v AC output, single phase at 1600Hz, rated at 360VA. I guess it dates from the 1960s cold-war era.
Many thanks,
Andy
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Old 21st May 2012, 3:53 pm   #2
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Default Re: Inverter Type 200

A lot of aircraft instruments use 115v three phase, usually 400Hz, sometimes higher.

Lighter aircraft use 28v DC systems.

Sounds like a unit to allow regular big-boy-aircraft stuff to be used in lighter planes. electro-mechanical sercvos and remote instruments. Look up 'Magslip' It woulld take 360va to power half a panel of instruments along with various sensors. VA rating of these things is normally set about 3x or more the actual running load to allow for motor start demands.... Get in your plane, turn on the master switch and all your gyros want to spin up together....

David
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Old 21st May 2012, 4:18 pm   #3
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Default Re: Inverter Type 200

Hi David,

I'm not sure you're on the right lines there, but thanks for getting the discussion going.

Bear in mind this is a military unit, apologies, I didn't make that clear.

In the WW2 era most comms equipment ran on the aircraft 28v dc system using dedicated rotary converters, for example the T1154/R1155 on the heavy bombers, but the navigation and radar equipment, for example Gee or H2S ran on 80v at 1600 Hz sourced from an engine-driven alternator.

Jump forward to the cold-war era and a lot of equipment now followed the American lead and used three-phase ac of 115v 400Hz. This included the power for the instruments as you say.

I think this inverter was fitted to such aircraft as the Hawker Hunter and maybe the V-bombers (and others) as a 'half-way house' to power equipment which still needed 'hi-cycle' 1600Hz power. But I don't know for certain, and I have no information!

I want to use it to power a WW2 Gee system, although I need to reduce the 115v to 80v with a suitable transformer (the next problem!).

Andy
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Old 21st May 2012, 9:25 pm   #4
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Default Re: Inverter Type 200

Hi Andy, if you can work out the circuit it may be possible to reduce the excitation on the output alternator to get 80v, not 115v. These were often quite crude control systems.

Ed
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Old 21st May 2012, 9:27 pm   #5
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Default Re: Inverter Type 200

Sounds like you might need a beefy 100V line output transformer or similar!
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Old 21st May 2012, 11:54 pm   #6
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Default Re: Inverter Type 200

Thanks, Andy, I never knew that Gee was 1600Hz powered. Keeps the transformers small.

David
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Old 22nd May 2012, 10:28 am   #7
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Default Re: Inverter Type 200

Ed, that is an interesting idea!

I have accepted an offer from someone who has one of these units to make me an autotransformer - as he has one in use there should be no problems.

David, certainly wartime Gee with the R1355 receiver and Indicator Type 62, and its immediate derivatives, ran on 80v 1600 Hz. I imagine later versions (I don't think the Gee transmitters were switched off until the early '70s) used 115v 400Hz but I don't have any detailed knowledge.

The wartime H2S radar system also used 80v/1600Hz - this had many units and required a lot of power!

Andy
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Old 30th May 2012, 10:51 am   #8
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Default Re: Inverter Type 200

I have a generator from , I think, a Lancaster bomber. I was going to say a dynamo, but it has dc output and ac 80v 1600c/s 500w. One end is a conventional dynamo , 28v 100A and at the driven end is a so -called "induction alternator"
the alternator end has two stator windings, wound together, one is the output and one the exciter or field. The rotor part of the alternator has no electrical connection and is made from shaped laminations with a number of poles round the circumference. Quite how the frequency was kept constant is not clear since the engine (RR Merlin?) would be changing speed.
The high output power was achieved by ducting air from scoops at the front of the engine directly into air pipe connections on one end of the unit.
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Old 30th May 2012, 11:09 am   #9
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Default Re: Inverter Type 200

Hi Bill,

That sounds like a very interesting item!

Does it have any ID number or Stores Reference number on it?

I think the simple answer to the frequency is that it was not constant, and as you say varied with engine speed. It would be 1600c/s at a specific engine speed - I imagine it was geared to nominally turn at this speed with the engine running at cruise rpm.

If you are willing to part with this generator please send me a PM!

Andy
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Old 30th May 2012, 2:11 pm   #10
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Default Re: Inverter Type 200

Hi Andy,
I've just been and looked at it:

On the plate:

"RAF ref. no. 5U/2362
Type U.O,,E.D.
Dual Purpose generator
1200>2400cycles 1200VA
28VDC 100A 3000Watts

Made by Small Electric Motors (Canada) Ltd."

The serial number is prefixed "CAN"

i expect some expert will be along presently to dispute its origins.
Some years ago (maybe 30!!!) I attached it to a Lister D type engine, driven by a Vbelt direct off the flywheel rim. It was possible to start the engine using the generator as a motor from a 12v battery, as soon as the engine was up to speed it charged the battery and could supply an inverter for lighting etc. This was for when WW3 started, fortunately still waiting....
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Old 30th May 2012, 7:54 pm   #11
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Default Re: Inverter Type 200

Bill, that sounds to be quite a powerful generator!
I can't find any reference to Type U.O, E.D, unfortunately.
What did you use as a control box or regulator?
Andy
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Old 30th May 2012, 8:03 pm   #12
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Default Re: Inverter Type 200

Hi,

Don't worry about keeping to 1600Hz, the alternator output varied directly with engine speed, the 1600HZ would be at cruise RPM.

Ross
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Old 30th May 2012, 8:22 pm   #13
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Default Re: Inverter Type 200

I could be wrong (I often am!) but I think aircraft engines have a fairly narrow rev band. A lot of the power variations are done by changing propeller pitch. Some sort of friction drive could maintain a sensibly constant frequency.
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Old 30th May 2012, 8:36 pm   #14
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Default Re: Inverter Type 200

Compared to car engines, aircraft engines get used over a fairly narrow range of revs.

The sorts of planes with AC power systems will also have variable pitch props. Higher revs will get used on take-off, and then it's all pretty much constant-speed work.

Even with a turbine engine, the curve of power versus shaft RPM is rather abrupt, so the range of revs used is moderate.

Combined alternator/dynamos were normal until relatively recently because they were proven. Even if you were mostly AC on a plane you still used a dynamo for battery charging. You needed a battery for engine starting and for reserve power for various things in case the alternator went south. Quite a number of instruments have been pneumatically driven (gyros spun for horizons and compasses) but electricity is still needed for the light to see them by. Murphy dictates failures will happen at night..

Cheers
David
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