50Hz to 60Hz Sine Wave Converter

[boba]

I have some US equipment that I want to use in the UK.
I want to transform 250v, 50Hz to 110v, 60Hz at around 500W.
The equipment has a number of small motors and I expect that it will need a good sine wave supply rather than the more common semi-rectangular approximation. (So similar to the units sold by gohz.com).
Anyone designed anything similar?

[medik]

I have used many US gadgets rated at 110Vac 60Hz on a 220Vac 50Hz line simply by stepdown transformer at ratio 2:1.
The frequency of 50Hz didn't affect the performance of my machines.
If frequency is critical,  it would mean building or buying an online inverter that utilizes DC from rectified AC input.

[Gallymimu]

There are many cases where the frequency is VERY important:

Anything with a timing circuit that relies upon line for timing
Anything with a linear iron core transformer (the volt-seconds applied at 50Hz is higher than at 60Hz even for the same voltage, power transformers are often designed on the very edge of suitable maximum flux before saturation so the additional volt-seconds CAN cause core saturation which might be a benign as the transformer getting hotter all the way to transformer failure)
Motors that are powered directly off of the line current.


There are 2 basic ways to convert 50Hz to 60Hz
1 is through a mechanical system that actually transforms the power mechanically through a rotary frequency converter:
http://www.temcoindustrialpower.com/product_selection.html?p=about_frequency_converter

The other way (which is simpler by today's standards) is through a SMPS converter / inverter stage similar to what medik said:  Convert to DC then invert back to AC at lower frequency. 

It's not a trivial SMPS design but at 500W it's not that hard for an experienced power designer.  I would not recommend it for a novice or even an EE who isn't quite good at SMPS and inverter design.

The best way to deal with this is to determine if you REALLY need a converter at all.  If you have small motors they likely run off an internal DC bus and you very likely have off the shelf SMPS power supplies that could either be replaced, or that already can accept 50Hz or 60Hz.  If you are talking about design I presume you can open the system up and verify the need.

[Old_but_Alive]

if you really need 60Hz, then how about a cheap $20 sine wave generator

http://www.ebay.co.uk/itm/DDS-Function-Signal-Generator-Module-Sine-Square-Sawtooth-Triangle-Wave-case-/272393711494?hash=item3f6bee2f86:g:8sYAAOSwNRdX6-kX

then a class D audio power amp feeding into a 28Vac to 115vac transformer.

$25 for 360watts

http://www.ebay.co.uk/itm/272422277235?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

[Sideshow Bob]

Another solution may be to use an electric motor to power an AC generator

[kukumar]

I have modified Fax machine ,from US to EU power.
110V is not problem -trafo 230 to 110V
US fax need 60Hz impulse, I make generator 60Hz (using NE555) and via opto coupler send this impuls to Fax(you must find that input to processor)
Fax is workong ok.

[CocaCola]

I have modified Fax machine ,from US to EU power.
110V is not problem -trafo 230 to 110V
US fax need 60Hz impulse, I make generator 60Hz (using NE555) and via opto coupler send this impuls to Fax(you must find that input to processor)
Fax is workong ok.

In a non-critical timing application that will probably suffice, but a 555 combined with what are generally sloppy tolerance caps and resistors (especially over time and temp changes) is probably not the best timing option...

[bigtoy]

A double-conversion UPS will give you a nice 50 Hz sine wave output. For example, if you had a US-style UPS, you could feed it in the UK using a step-down transformer. (I'm assuming the UPS won't accept a 240V input.) The UPS will accept 60 Hz input, and will give you 50 Hz output. Note however this will only work with double-conversion UPSs, not line-interactive UPSs.

Along a similar line, an automotive AC power inverter would give a similar result. Use an automotive battery charger to generate 12V DC at lots of amps, and use that to power a (US style) automotive AC inverter to give you 120V 50Hz.

[boba]

Thanks for the inputs. Its an antique bit of military kit, the motors do need to run at 60Hz otherwise there will be a lot of changes needed to the gear trains which I likely can't address. I did think of using an inverter but I had thought that generally they weren't very good sine generators. The idea of a UPS might be a good one - I'll try to investigate this a bit further. I'm really a (ex-)chip designer so not much experience of power electronics.

I do have a 50Hz/60Hz generator in the workshop but it's a bit of a noisy smelly solution .

[kreutz]

It all depends on how much time and money you are willing to invest into a permanent solution.
Reply #4 is a simple and viable solution. If you don't want to get into a mechanical speed conversion between the motor and the generator (nominally 3000rpm into 3600 rpm at the generator's input shaft) you can get a 1KVA 3 phase motor and use a cheap 1.5KVA (single phase input 3 phase output) VFD to drive it. That way you can precisely control the generator's output frequency without mechanical complications. It also makes the solution more compact (direct shaft to shaft coupling).
You might also need a 220Vac to 120Vac 1KVA power transformer depending on the generator's output voltage.