# 240v to 110v transformers



## jogguk (Sep 5, 2010)

OK Here is a weird one been bugging me for years I am sure Mildred will have the answer

My imported American Campervan has the usual 110v appliances A/C, microwave, battery charger/converter etc, etc. However, when I purchased it I specified the unusual factory option of a 240V 2.3 Kw Onan onboard generator (normally for the US market it is the popular Onan 2.8 110v model) and 240v hook up with interior sockets.

I stress this is a Canadian built factory option nothing I have fiddled with So 240v genny feeding two (smallish quality looking transformers) one exclusively for the A/C and the other for the appliances. The converter/ battery/charger I think to be 240v, but maybe 110v off the transformer too, but works OK on EHU and genny so irrelevant to my "problem"

"The problem" 
I think the genny has been modified to put out 240v at 60 cycles (UK is 50 cycles) so that it runs through the transformer to give 110v @ 60cycles so their cheepo Samsung microwave works  I think this because when used on EHU (240v @ 50 cycles) the Microwave smells like fried circuit boards and therefore can't be used eek:  

Everything else works OK  I can't dump the microwave for a UK one because then I will have the reverse problem How can I test the output of the genny ??? Are all microwaves that frequency sensitive?

John


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## The Grand Wanderer (Sep 5, 2010)

The short answer is that 60 cycle microwaves do not like anything other than the current they are designed for. I found this link on the net may help you to understand.
Wanderer


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## jogguk (Sep 5, 2010)

The Grand Wanderer said:


> The short answer is that 60 cycle microwaves do not like anything other than the current they are designed for. I found this link on the net may help you to understand.
> Wanderer



Thanks for that link. This bit sort of answerwed my question:

_*The magnetron tube is set to work on 60 Hz.
The tube itself works on DC--actually pulsed DC in practice, to be precise. It doesn't really care what the line frequency is. All the control electronics also run on DC, which is rectified from the output of a small transformer, usually on the main circuit board. 

The components most affected by the change in line frequency are the transformers, in fact. Nevertheless, most transformers designed to work on 60 Hz will also work just fine for 50, and vice versa. There is a caveat, however: a transformer's power handling capacity is based on frequency and core size (in large part). Thus, in general, a transformer with a given core size will handle less power as the frequency drops. This is the reason aircraft normally use 400 Hz power--the transformers, motors and other inductive components can be much smaller and lighter than their 60 Hz counterparts. In aviation weight is everything. The point is, that if the transformer is being driven at its maximum power-handling capacity on 60 Hz, then running on 50 Hz may overwork it, and cause failure.*_

After further investigation The Onan Generator  I.D. plate definately states model number 2.3KVFR33742J   2.3 Kvh  240v 50 Hz. The  Systens Monitor TMC 300D 30amp converter has a sticker on it stating "for UK use only" and the I.D. plate has been crudely altered to show 240v 50Hz (feeding two 110v transformers) 

So, if the above is correct the US  m/wave  being 60Hz shouldn't work But it does, 9.5 years old still going 

I could try a UK m/wave plugged ito one of the 240v sockets fed from the genny to see what happens I supose

John


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## The Grand Wanderer (Sep 5, 2010)

I could try a UK m/wave plugged ito one of the 240v sockets fed from the genny to see what happens I supose


That would be my option of choice as can also be used on EHU
Wanderer


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## jogguk (Sep 5, 2010)

The Grand Wanderer said:


> I could try a UK m/wave plugged ito one of the 240v sockets fed from the genny to see what happens I supose
> 
> 
> That would be my option of choice as can also be used on EHU
> Wanderer



Hmm, But I don't want to install TWO m/waves 
Caravan sites and EHU has always been the unattractive option

There has to be a simple explanation to why it dont work on EHU I mean on  site I just unplug the 6 metre hard wired lead (standard blue plug 16amp UK) from the converter to genny and plug into the site box instead. Everything works except the m/wave (which works but a burning circuit board smell accompanies it

John


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## guyd (Sep 5, 2010)

why not adjust the genny to 50Hz? Then buy a UK microwave?


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## jogguk (Sep 5, 2010)

guyd said:


> why not adjust the genny to 50Hz? Then buy a UK microwave?



How is this done?


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## The Grand Wanderer (Sep 6, 2010)

Just a thought, but is the polarity of the lead that you unplug from the geni to put in the EHU post on the site correct for the converters and thus for the microwave?


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## jogguk (Sep 7, 2010)

The Grand Wanderer said:


> Just a thought, but is the polarity of the lead that you unplug from the geni to put in the EHU post on the site correct for the converters and thus for the microwave?



Interesting thought Not knowing much about m/wave ovens would reversed polarity cause them to overheat

At least I can check this out with a multi meter, checking for 50 or 60 Hz is not something I have equipment for

john


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## The Grand Wanderer (Sep 7, 2010)

Right let me recap.

Your microwave is rated at 110 volts 60 cycles, and smells when you use 240 volts provided by EHU via one of the converters.
Your generator produces 240 volts at 50 cycles.
Your two converters each provide 110 volts at 50 cycles.

So how would you need two microwaves if you bought new one using 240 volts at 50 cycles. It would work perfectly whether the power was coming direct from the genni or from the EHU.


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## Deleted member 5816 (Sep 7, 2010)

Just a thought because posts not that clear but is the 110v microwave being plugged into a 240v socket
 hence the burning smell ?
Alf 1


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## jogguk (Sep 7, 2010)

Alf 1 said:


> Just a thought because posts not that clear but is the 110v microwave being plugged into a 240v socket
> hence the burning smell ?
> Alf 1



No The m/wave is via a 110v transformer From EHU or genny. As far as I know transformers wont change the frequency.



> "The problem"
> I think the genny has been modified to put out 240v at 60 cycles (UK is 50 cycles) so that it runs through the transformer to give 110v @ 60cycles so their cheepo Samsung microwave works I think this because when used on EHU (240v @ 50 cycles) the Microwave smells like fried circuit boards and therefore can't be used eek:



John


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## jogguk (Sep 7, 2010)

The Grand Wanderer said:


> Right let me recap.
> 
> Your microwave is rated at 110 volts 60 cycles, and smells when you use 240 volts provided by EHU via one of the converters.
> Your generator produces 240 volts at 50 cycles.
> ...



Isn't that what I first said  I may be confusing you with my terminology The *transformers* (not converters) hopefully are just that 240v to 110v and they do not change frequebcy (Hz).  

The *converte*r is the big power distribution unit with fuses for the 12v circuits, breakers for the 110v circuits and a battery charger to charge the leisure battery. It also acts as a 240v AC to 12v DC *converter* so all the 12v loads from the battery are automatically switched and powered from the EHU or genny (unlike a Zig unit for example)  This converter has a long lead with UK blue plug, can be pluged into the site EHU or coiled up in the locker and pluged into the genny, which is built in under the floor. Is this making any sense 

john


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## The Grand Wanderer (Sep 8, 2010)

Great, now we know exactly how your set up is put together.

I have an idea as to how to find out for sure what your genni is producing by way of Hz without using an ocilloscope.

Plug in a standard 240v 50Hz electric clock when the genni is running and set to correct time. Leave for one hour and then look at clock again if clock fast then genni is producing 60Hz if clock ok then genni is 50Hz.


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## Deleted member 5816 (Sep 8, 2010)

The Grand Wanderer said:


> Great, now we know exactly how your set up is put together.
> 
> I have an idea as to how to find out for sure what your genni is producing by way of Hz without using an ocilloscope.
> 
> Plug in a standard 240v 50Hz electric clock when the genni is running and set to correct time. Leave for one hour and then look at clock again if clock fast then genni is producing 60Hz if clock ok then genni is 50Hz.


 
or find an electrician with a Hz meter most top quality multimeter come with Hz on them 
I must admit I have only checked Hz a few times with mine 
there are not many Hz clocks about now mainly battery   I suppose a car boot may provide one.


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## guyd (Sep 8, 2010)

The US use both 240 and 110v - most donestic stuff is 110 - but they use 240 for more industrial stuff - very confusing.

If its a US genny - it will be set to 60Hz - as thats what they use. Its easy - as demonstrated - to go from 240 to 110 and visa versa.

In order to alter the frequency, you will need to alter the generator's controls - this will either be a mechanical control (often a 'fan' which blows a vane - often used on briggs and stratton lawnmowers) - or an AVR controller might have control over the engine. Take some covers off - and see what you can see?


Quick google - first result reveals:-





* On the speed/frequency issue: first, take a close look at the genset when it is running with no load - the idle stop screw should NOT be touching, i.e. pressing the throttle lever back against the idle stop should lower the speed to 55 hz, and there should be visible space between the screw and the lever. Adjust this as necessary.

* Next, with the genset stopped, unclip the governor linkage rod from the throttle lever and check that the rod goes in the hole on the throttle lever with the throttle lever just short of being wide open throttle. Adjust the rod length if necessary by loosening the locknut on the other end of the rod (where it threads into the ball and socket joint), turning the rod into - or out of - the joint as needed, then re-tighten the locknut and clip the rod back into the throttle lever.

* Looking at the governor mechanism, you'll see an arm extending outwards, pivoting on a shaft coming up vertically out of the engine, with the ball and socket joint on the end closest to you. About 2/3 of the way down the arm, you'll see a spring extending to the right, with the left end hooked to a link that's threaded on a screw mounted in the arm and the right end hooked to a threaded rod that goes thru a stationary bracket, with a nut on the other side of the bracket. This nut is the speed adjustment nut - by controlling the tension on the governor spring, it controls the speed of the genset.

* The screw mounted in the governor arm is the sensitivity adjustment screw - by moving the point where the governor spring is attached to the arm, it changes the governor sensitivity. With no load, adjust the speed adjustment nut for 62-63 hz. Apply full load - the speed should be at least 58 hz. Spec calls for 2-4hz drop from no load to full load, but in my experience, trying for anything less than 3hz makes the gen unstable at some load levels (whoop whoop whoop as it accelerates/decelerates but never settles on a stable speed). If your drop from no load to full load is more than 4hz, adjust the sensitivity screw counterclockwise by 1-2 turns, re-adjust the speed nut, then test drop under full load again. Continue until no-load to full-load drop is under 4hz. Do note that this presumes carburetor mixture screws are correctly adjusted first:

* With the genset fully warmed up, apply a full 4kw load. Turn the main adjustment inward until frequency drops slightly. Turn main adjustment outward until frequency drops slightly. Locate the point where frequency is highest (approx midway). From this point, turn the adjustment out another /4 turn. Remove the load. Allow genset to stabilize for 30sec-1min, then turn the idle adjustment screw in _slowly_ until frequency drops and engine begins to run rough or starts hunting. Back out the idle adjustment screw as required for smoothest running/highest frequency without hunting (may take 1/8 - 1/4 turn out from highest frequency to keep set from hunting on sudden load removal). Test with various loads, and transitions between various loads, to ensure stable operation under all conditions. 





YMMV.
Guy


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## jogguk (Sep 8, 2010)

guyd said:


> The US use both 240 and 110v - most donestic stuff is 110 - but they use 240 for more industrial stuff - very confusing.
> 
> If its a US genny - it will be set to 60Hz - as thats what they use. Its easy - as demonstrated - to go from 240 to 110 and visa versa.



It is one of these  European market oneView attachment 1680



guyd said:


> In order to alter the frequency, you will need to alter the generator's controls - this will either be a mechanical control (often a 'fan' which blows a vane - often used on briggs and stratton lawnmowers) - or an AVR controller might have control over the engine. Take some covers off - and see what you can see?
> 
> Quick google - first result reveals:-



I think they're talking about a 4KW Emerald genny.  

Although the genny was installed by the Canadian M/H builders it was a Euro spec. model. They had done a few before apparently for the German market. Still It would be a bit naughty of them to tweak the frequency just to get the poxy m/wave working Also in with the big wad of manuals was a ECC certificate of conformity for the genny too

I/m going to see If I can borrow, beg or steal a multi meter with a Hz display  Checked all the wiring today to the power sockets IIOv & 240v, output from genny and on EHU. No reversed polarity.

john


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## guyd (Sep 10, 2010)

Ok - might be the wrong model -- buts it will be very similar in principle.


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