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'[EE] Generating 120Vac 50Hz'
2009\07\06@100832 by Mark Scoville

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Hi Piclisters,

I have a project at work that I need to test while powered from 120Vac 50Hz.
All I have available in the USA (Cleveland, Ohio) is 60Hz. Does anyone have
any clever and inexpensive ideas for how to generate 120Vac 50Hz? I need
about 4 amps to do my testing.

So far my thought is to buy a "Modified Sine" inverter ($100) that runs off
12Vdc and produces 220Vac at 50Hz. Then I could step down the 220Vac using a
transformer (which we already have). It's not very elegant, and not ideal,
but this is only needed for a few days of testing and then will probably sit
on a shelf for 20 years getting dusty.

Anybody have any other ideas besides a really long extension cord to a
country that uses 50Hz.

-- Mark



2009\07\06@102855 by Carl Denk

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Rent or borrow a small portable generator, set the governed engine speed
down to provide the necessary frequency. Many times the voltage is
regulated so it still will be there. Would need to check if this is
possible with the generator you have available. Some generators have a
jumper or wire settings. Just a thought of brain storming. :)

Mark Scoville wrote:
{Quote hidden}

2009\07\06@103346 by M.L.

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On Mon, Jul 6, 2009 at 11:09 AM, Mark
Scoville<spam_OUTmscovilleTakeThisOuTspamunicontrolinc.com> wrote:
{Quote hidden}

Link two AC induction motors by a set of pullys and a V belt. The
frequency (also voltage) should be somewhat lower than 60Hz due to
slip. You will have to momentarily flash the field to start the
magnetic field on the generating side. If you had a DC series motor
(or ACIM + VFD) you could spin it at a variable speed to ensure that
it stayed at the frequency you desire.

I expect that the voltage will be lower than you would want to deal
with in this case. I just thought I'd throw out a cheap option if you
have the parts.

--
Martin K.

2009\07\06@103727 by Marcus - PP5MS

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Hello Mark,

120Vac by 4 Amps is about 480Watts.

Since you need just for a few days fos a test, it is possible to use the
follow sertup:

Audio generator on 50Hz. connected to one power audio amplifier (P.A. system
500 Watts) where you coneccted one power transformer on the output of the
amplifier to have your 120Vac in 50Hz.

This kind of amplifier is easy to rent for a few dais and I think you can do
this with a low cost.

This is my idea, hope this can help you.
Regards,
Marcus


{Original Message removed}

2009\07\06@103945 by Harold Hallikainen

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Not very practical for your application, but about 50 years ago, my
father's company (http://sujan.hallikainen.org/hi/ ) had an interesting
way of generating 50Hz for equipment they shipped outside the US. This was
process chemical analysis equipment for oil refineries. It measured
viscosity, boiling point, specific gravity, color, etc. of petrochemicals.
Their method of generating 50Hz consisted of two three phase motors
connected together. One would rotate the other at a relatively slow speed.
On the one being rotated, they drove the armature (I think it was) with
60Hz. They got 3 phase 50 Hz off the field windings. The rotation of the
shaft subtracted 10Hz from the 60Hz.

There is, of course, test equipment to generate various line frequencies.
My former employer had a couple of these units. I used them a lot in the
design and testing of phase control light dimmers. In those dimmers, the
PIC would time between zero crossings of the AC line on power up, then
decide which table to use in converting from DMX values to timer clicks.

Your idea is probably the simplest. Are the 50Hz countries you're shipping
to 120V or 230V? It seems that most 50Hz countries use a 230V line, so you
would not need the transformer.

Good luck!

Harold



--
FCC Rules Updated Daily at http://www.hallikainen.com - Advertising
opportunities available!

2009\07\06@113458 by Tony Vandiver

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Hi Mark,

   I've rented equipment like this when I didn't want to spend the
money on something I wouldn't use for long.  I've used one like this on
ebay (for $2250) that can generate 0-270VAC and something like 30 to
120Hz from a straight 120VAC 60Hz input.  There's also one with a serial
port, but I never used it - anyway I'm always wishing I had one for my
own business :

http://cgi.ebay.com/BEHLMAN-P1351-AC-POWER-SOURCE-INVERTER-0-270VAC-1350A_W0QQitemZ200357461348QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item2ea63c3d64&_trksid=p3286.m20.l1116

Tony


Mark Scoville wrote:
{Quote hidden}

2009\07\06@114628 by Charles Craft

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I worked for a company that builds railroad equipment that uses 50Hz.

Their solution for the lab was to couple the shaft from a 110/220 motor to
a small 50Hz generator, bolt it to a platform and stick it up in the rafters.

{Original Message removed}

2009\07\06@115609 by peter green

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> Anybody have any other ideas besides a really long extension cord to a
> country that uses 50Hz.
>  
You could get a generator designed for UK construction site use, they
will have a 110V 50Hz output (it is center tapped earth though which may
be an issue in some very unusual circumstances)

2009\07\06@124439 by Dwayne Reid

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At 09:09 AM 7/6/2009, Mark Scoville wrote:
>Hi Piclisters,
>
>I have a project at work that I need to test while powered from 120Vac 50Hz.
>All I have available in the USA (Cleveland, Ohio) is 60Hz. Does anyone have
>any clever and inexpensive ideas for how to generate 120Vac 50Hz? I need
>about 4 amps to do my testing.
>
>So far my thought is to buy a "Modified Sine" inverter ($100) that runs off
>12Vdc and produces 220Vac at 50Hz. Then I could step down the 220Vac using a
>transformer (which we already have). It's not very elegant, and not ideal,
>but this is only needed for a few days of testing and then will probably sit
>on a shelf for 20 years getting dusty.

Many of our local stores sell vehicle power inverters - I'm thinking
of Canadian Tire but there are others.  400 Watt 120V inverters go on
sale for about Can $25 on a regular basis.  I also purchased a 1000
Watt model for Can $75 a couple of years ago.

Its a very simple process to go inside and change a single resistor
to move the output frequency from 60 Hz to 50 Hz.

The downside of using those cheap inverters is that the so-called
modified sine wave output is really nothing more than a 150V peak
square wave with lots of dead time.  They do it that way so that the
peak and average values match a real sine-wave source.

It actually works quite well but you need to be aware of the limitations.

FWIW - we purchased about a hundred of those cheap 400W inverters
last year - we go inside and grab the regulated 150Vdc for use in one
of our pipeline transmitters.  Same deal as with lots of other stuff
- we can't purchase and assemble a 150 Vdc 4 Amp dc-dc inverter for
anything close to $25.

dwayne

--
Dwayne Reid   <.....dwaynerKILLspamspam@spam@planet.eon.net>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
(780) 489-3199 voice          (780) 487-6397 fax
http://www.trinity-electronics.com
Custom Electronics Design and Manufacturing

2009\07\06@202033 by Harold Hallikainen

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> FWIW - we purchased about a hundred of those cheap 400W inverters
> last year - we go inside and grab the regulated 150Vdc for use in one
> of our pipeline transmitters.  Same deal as with lots of other stuff
> - we can't purchase and assemble a 150 Vdc 4 Amp dc-dc inverter for
> anything close to $25.
>

MANY years ago, a local company (Cuesta Systems) made power inverters for,
I think, the Osborne computer. They generated +/-150VDC. I bought these to
use in another product. I bridged the output of this across the series
capacitors after the rectifier in a switchable 120/240V power supply (not
universal input). This power supply powered the system. The inverter
powered the system when AC went away. We charged a 12V SLA battery from
the +5V and -12V with a linear regulator setting the float charge voltage.
We also sensed the battery current. When it indicated the battery was
being discharged instead of charged, we shut down the charger.

Harold


--
FCC Rules Updated Daily at http://www.hallikainen.com - Advertising
opportunities available!

2009\07\07@090154 by Mark Scoville

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Thanks to everyone that made suggestions for generating 120Vac 50Hz...

The motors and pulleys idea is nice, but we don't have any motors and
pulleys lying around :-(

The PA amplifier idea might work, but my boss doesn't want to go that route.

Someone mentioned a possibility that some generators have a 50/60 Hz jumper
inside. Me and a couple other guys here have generators at home, so we'll
take a look and see if any of them have a frequency jumper or any other way
to change the frequency.

We'll look at he cost of renting something to do the job. If the cost of
getting the "right" equipment is too much we'll probably go with a Modified
Sine Inverter that puts out 50Hz (about $100)

Our prospective customer is in Africa - I am told they have 220V 50Hz power.
The customer is aware that our equipment requires 120Vac and they are
prepared to use a step down transformer to get the 120Vac. The question is
whether our equipment is still within spec when powered from 50Hz. It was
not specifically designed to operate at 50 Hz, but the transformers on our
boards are 50/60Hz units.

Thanks for all the good ideas.

-- Mark




2009\07\07@094726 by Alan B. Pearce

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>Our prospective customer is in Africa - I am told they
>have 220V 50Hz power. The customer is aware that our
>equipment requires 120Vac and they are prepared to use a
>step down transformer to get the 120Vac. The question is
>whether our equipment is still within spec when powered
>from 50Hz. It was not specifically designed to operate at
>50 Hz, but the transformers on our boards are 50/60Hz units.

If your transformers are a bit light in the iron core for 50Hz, then a
possibility is to see how well it all runs at around 100V 50Hz.

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