Best method for testing 240v 50hz in the US? - Page 1
Forum section: electronics / testgear

author: ryanmills
author_rank: Unknown
timestamp: September 06, 2018, 08:53:49 pm
content: I live in the US and for testing something intended for standard mains power I have an isolation transformer (standard 120v 60hz). I need to start testing a variety of products we intend to ship to Europe and Asia and the 220-240v 50z arena and don't want to die in the process. The cheap ebay/amazon choices look like they will likely kill me and don't switch 60hz to 50hz. Any thoughts/recommendations on setting up something safer capable of 15-20 amps for this in the US? Its a real mix of products from fans to delicate electronics.

author: taydin
author_rank: Frequent Contributor
timestamp: September 06, 2018, 09:04:44 pm
content: Many online UPS's can do frequency conversion. You would just have to look for a model that can take in 120V and output 220V.

author: joeqsmith
author_rank: Super Contributor
timestamp: September 07, 2018, 12:45:39 am
content: Generator. So an AC motor, belt driving the generator. Pulley ratio sets the frequency. Quick search, something like this.https://youtu.be/m153TWFIetQ

author: korlatos
author_rank: Regular Contributor
timestamp: September 07, 2018, 12:47:53 am
content: FC2000-50 does the job, but is limited to 2000W:https://www.mdspower.com/products/frequency-converter-fc500-fc1000-fc2000

author: joeqsmith
author_rank: Super Contributor
timestamp: September 07, 2018, 01:00:54 am
content: OP was looking for 20A.Depending on the load, the inverters may not like it. The generator is fairly forgiving. We really don't know what the OP's loads are, just a mix.

author: edavid
author_rank: Super Contributor
timestamp: September 07, 2018, 01:11:07 am
content: Quote from: ryanmills on September 06, 2018, 08:53:49 pmA 20A unit is going to be expensive and heavy, but here is one supplier:http://www.gohz.com/single-phase-frequency-converter?orderby=10

author: IanB
author_rank: Super Contributor
timestamp: September 07, 2018, 01:19:49 am
content: A quick search turns up another supplier. There are probably many options, so market research is needed.https://www.georator.com/belt-coupled-motor-generator-sets.html

author: Richard Crowley
author_rank: Super Contributor
timestamp: September 07, 2018, 01:26:33 am
content: Why do we even care about mains frequency anymore?Surely nobody uses mains frequency for time/frequency reference here in the 21st century.And only the most marginally-designed transformers will be OK at 60 Hz but flaky at 50Hz.

author: IanB
author_rank: Super Contributor
timestamp: September 07, 2018, 01:55:49 am
content: Quote from: Richard Crowley on September 07, 2018, 01:26:33 amAnything with an induction motor?Also, if you were manufacturing a product for sale in 50 Hz markets, would you ship them without actually testing the design at 50 Hz with the expected supply voltage?

author: CatalinaWOW
author_rank: Super Contributor
timestamp: September 07, 2018, 02:03:52 am
content: Quote from: IanB on September 07, 2018, 01:55:49 amIf someone is testing for suitability and safety a single point test (one voltage and frequency) is hardly adequate. Would want to test max and min voltages and maybe some frequency variation. Adds to the requirements on what OP is looking for.

author: radar_macgyver
author_rank: Frequent Contributor
timestamp: September 07, 2018, 02:09:37 am
content: Quote from: Richard Crowley on September 07, 2018, 01:26:33 amProbably true for the OP's case (20 A load) but once the transformers get larger (than, say, 25 kVA), they design them pretty close to the limit because the steel cost goes up substantially to go from 60 to 50 Hz.

author: Tom45
author_rank: Frequent Contributor
timestamp: September 07, 2018, 03:29:12 am
content: Our larger machines are designed to customer's requirements for voltage, frequency, and single vs. 3 phase. For jobs that can't be tested with some variant of shop power, we rent a trailer mounted diesel motor generator. The voltage and frequency can be dialed in at its control panel. Certainly for export to 50 Hz countries, we need the MG set. Not much fun to ship something across the Pacific ocean and then find out at the other end that it has problems with the local power.I don't know who makes it, but you should be able to find what you need by looking for industrial equipment rental places.

author: tomato
author_rank: Regular Contributor
timestamp: September 07, 2018, 04:13:49 am
content: We use a Pacific Power Source AC power supply for the same application. Very versatile and it's been bombproof:https://www.pacificpower.com/Resources/Documents/Combo_16pg_Brochure_Web.pdf

author: martinr33
author_rank: Frequent Contributor
timestamp: September 08, 2018, 04:59:45 pm
content: One thing that you cannot test easily is effects related to the surprisingly low impedance of UK 240V supplies. UK sockets - closer to 250V - are wired with a ring main, so each socket sits on a loop of wiring that has two paths to the fusebox. This approach means that the wall socket can deliver a LOT of inrush current.Therefore, any bridge rectifier- capacitor combination has to be ready for such an inrush. It can blow diodes, even beefy ones. This is why you will often see a thermistor in series, to limit this inrush.I discovered this the hard way, witha CRT design where the degaussing coil was across the rectifier bridge. This approach converted the bridge into a voltage doubler for a couple of cycles. In the US, this didn't matter on a 240V transformer supply.In the UK, it charged the capacitors to 800V - and took out the switch transistor, and blew the DC current limiter resistors into dust.

author: james_s
author_rank: Super Contributor
timestamp: September 08, 2018, 05:21:40 pm
content: In one of my side gigs, we use a boat anchor power supply that is essentially a gigantic audio amplifier made with rows and rows of TO3 transistors driven by an oscillator that produces a 50 or 60Hz sine wave. The thing is the size of a dorm fridge and weighs a few hundred pounds but it does the job. I don't remember offhand how much current it can supply, we use it to test 6.6A series loop transformers and ballasts.

author: Stray Electron
author_rank: Super Contributor
timestamp: September 08, 2018, 07:22:26 pm
content: Where are you in the US? I have an extra Elgar 251C that I'd sell but it's heavy as hell and I don't really want to ship it. You can look up the specs and the manual on line but these output variable voltage and variable frequency AC. My units are single phase but I can get a larger three phase unit.What kind of VA do you need?

author: duak
author_rank: Super Contributor
timestamp: September 08, 2018, 08:16:45 pm
content: About 25 years ago when the company I worked for was quite small, we rented a 50/60 Hz power supply for testing. It was kind of a UPS but it was designed for supplying power for test purposes. I can't remember the name of the manufacturer. The company grew and we ended up buying it off the rental company.The equipment we tested was ostensibly designed for world wide operation, but testing showed some parts weren't up to the task.examples:- an oilless compressor that had a resonant piston. At 50 Hz, the pressure was about 50% of that at 60 Hz. It was expected to be about 5/6 due to the frequency reduction.- the main power transformer on one product kept tripping the two pole circuit breaker when the transformer was wired for 120 V in. Turned out the primaries were not specified to have the exact same number of turns and so the manufacturer didn't guarantee it. If the primaries had different numbers of turns, a parasitic circulating current flowed in them, tripping the breaker.- AC operated cooling fans ran slower on 50 Hz and the product would tend to operate a bit hotter than on 60 Hz.Cheers,

author: IanB
author_rank: Super Contributor
timestamp: September 08, 2018, 08:18:49 pm
content: Quote from: martinr33 on September 08, 2018, 04:59:45 pmAdded to this the substation transformers in the UK may be quite large, a single transformer supplying hundreds of houses with fat copper cables distributing the power to the consumers. When people say the mains has nearly zero source impedance they are not kidding.

author: james_s
author_rank: Super Contributor
timestamp: September 09, 2018, 02:46:09 am
content: Quote from: IanB on September 08, 2018, 08:18:49 pmThat's something I was surprised to see, being accustomed to the way it's done here in the US with 7200V lines right up to the pole or vault mounted transformers that feed just a handful of houses within close proximity. My UK friend was monitoring his mains voltage for a while and found it to vary by a significantly larger percentage than mine.

author: ryanmills
author_rank: Unknown
timestamp: September 12, 2018, 04:50:28 pm
content: Thank you everyone, I have plenty to look at!

author: David Hess
author_rank: Super Contributor
timestamp: September 13, 2018, 12:17:08 am
content: Like taydin says, some online UPSes can be set to produce a different output voltage and current from their input. A 20 amp 240 volt UPS is not going to be inexpensive but none of the solutions will be.If you are going to test frequency, then you should also include testing at minimum and maximum line voltage. An inexpensive buck/boost transformer could be used to adjust the output of a constant voltage source.

author: nfmax
author_rank: Super Contributor
timestamp: September 13, 2018, 12:32:49 pm
content: One of these?https://www.keysight.com/en/pdx-2753894-pn-AC6804A/basic-ac-power-source-4000-va-270-v-20-a?nid=-32116.1216491&cc=GB&lc=eng&pm=ov

author: Jeroen3
author_rank: Super Contributor
timestamp: September 13, 2018, 01:08:51 pm
content: Quote from: IanB on September 07, 2018, 01:19:49 amYou don't even need the belt. You can use directly coupled and a VFD. Might be more suitable on light mains supplies, considering the inrush of those things.Plus, you get variable frequency control! You can go 0 to 70 Hz easily, considering proper derating.If you get a better voltage regulator, you can adjust the voltage as well, add current limiting or current trip. We've build some of them.

author: Neomys Sapiens
author_rank: Super Contributor
timestamp: September 13, 2018, 08:42:11 pm
content: There is a company called Spitzenberger & Spies which builds such power supplies.You get what you want, with spikes on top, if needed.One phase, three phase, 50/60/400Hz, brown out, frequency deviations, you name it...

author: taydin
author_rank: Frequent Contributor
timestamp: September 13, 2018, 09:25:13 pm
content: Quote from: nfmax on September 13, 2018, 12:32:49 pmIt has wide range voltage and frequency adjustment, but no current limit adjustment. So effectively, it's just a $15,000 4KVA online UPS