Recommendations for three phase variable inverter transformer / variac - Page 1
Forum section: electronics / testgear

author: exit_failure
author_rank: Regular Contributor
timestamp: February 06, 2023, 10:37:21 am
content: For compliance testing purposes I am looking for recommendations for a device that integrates a inverter and an adjustable transformer.The thins I absolutely need arethree phasesmin. 125A/67kVA output capabilityat least 200V - 530V output rangeI found the Chroma 61800 series (https://www.chromaate.com/de/product/regenerative_grid_simulator_61800_series_161) but this device has much more functionality than I need. All I need is an adjustable transformer that can switch between 50Hz and 60Hz output frequency.Ideally the device should be as small and light as possible. Ideally the price should be under 100.000€.Thanks for your help!

author: jonpaul
author_rank: Super Contributor
timestamp: February 06, 2023, 11:17:47 am
content: HelloMost variable transformers are designed for 50/60 Hz use, à 50Hz transformer is fine on 60 Hz.At the power level you mentioned the cost of the unit and freight will be 1000s €\$ not 100.For a single qualification test, find an equipment rental house, preferably local.Inverters at these power levels are very large,and even more costly.The inverters are capable of any frequency to 1kHz, so 8f 50 and 60 Hz is needed they are usefulBesides a variable transformer, consider a 3 phase generator.Bon chanceJon

author: exit_failure
author_rank: Regular Contributor
timestamp: February 06, 2023, 12:02:35 pm
content: Quote from: jonpaul on February 06, 2023, 11:17:47 amI need one where I can switch theoutputfrequency.Quote from: jonpaul on February 06, 2023, 11:17:47 amUp to 250k€ is ok. Under 100k€ would be preferable.Quote from: jonpaul on February 06, 2023, 11:17:47 amI work at a compliance test lab. That's why I'm looking for one.

author: Jeroen3
author_rank: Super Contributor
timestamp: February 06, 2023, 12:57:20 pm
content: Have you consideredbuyingor building a rotary converter with adjustable excitation?

author: Hawaka
author_rank: Regular Contributor
timestamp: February 06, 2023, 01:15:11 pm
content: Have a look at Regatron (https://www.regatron.com) or Gustav Klein (https://www.gustav-klein.com/en/). They both have AC programmable source in that power range (or more), and will be less expensive than Chroma (at least Regatron last time I look).I think one of the key factor will be your input type. Single phase, three phase, what voltage? Changing the frequency is easy, but if your input voltage once rectified is less than your max. peak output voltage, then you will have for sure to pay more to get a supply that integrate a DC boost module. Also if you need to be regenerative that will increase considerably the price.

author: Zero999
author_rank: Super Contributor
timestamp: February 06, 2023, 01:27:53 pm
content: Quote from: exit_failure on February 06, 2023, 12:02:35 pmThen the answer is no, a transformer cannot change the frequency. An active device such as an inverter or rotary converter is required to change the frequency.

author: exit_failure
author_rank: Regular Contributor
timestamp: February 06, 2023, 01:44:23 pm
content: Quote from: Jeroen3 on February 06, 2023, 12:57:20 pmMay that would be an option. Those are only frequency inverters and would require an additional variable transformer, correct?

author: exit_failure
author_rank: Regular Contributor
timestamp: February 06, 2023, 01:46:45 pm
content: Quote from: Hawaka on February 06, 2023, 01:15:11 pmThe Regatron look interesting. I asked them for more information. The Gustav Klein ones unfortunately are too bulky - at least the ones that I could find on their homepage. Thanks you :-)The Input will be three phase 380V.

author: Jeroen3
author_rank: Super Contributor
timestamp: February 06, 2023, 02:34:31 pm
content: Quote from: exit_failure on February 06, 2023, 01:44:23 pmNot necessarily. Most are a coupled motor generator. The motor speed can be varied by a frequency drive, a cheap one for induction motors. The generator can be a brushless type with an AVR that you can use to adjust the output voltage.The motor and frequency drive can be downsized if you don't need the kW. You may even be able to rent one, depending if it's a recurring job.If you want you could even use a rental diesel genset.True, this is not the smallest option. An inverter power supply is smaller. But a lot more expensive.A rotory converter can probably be found used somewhere, or welded together by a local shop.

author: Zero999
author_rank: Super Contributor
timestamp: February 06, 2023, 06:29:49 pm
content: Quote from: Jeroen3 on February 06, 2023, 02:34:31 pmWhy would you put a motor-generator set on a VFD? Wouldn't it make more sense to just add a transformer to the output of a VFD?

author: Jeroen3
author_rank: Super Contributor
timestamp: February 06, 2023, 08:48:54 pm
content: You don’t direct start 150kVA… and you still need a way to change 50/60hz! Sure you can get another transformer, of many kilos, if you want.

author: Zero999
author_rank: Super Contributor
timestamp: February 06, 2023, 09:22:31 pm
content: Quote from: Jeroen3 on February 06, 2023, 08:48:54 pmI don't follow.My question is: why bother with a motor generator set, if you have a VFD? Why not just use an VFD and a transformer? It'll be much smaller than a motor generator set.

author: Jeroen3
author_rank: Super Contributor
timestamp: February 07, 2023, 07:05:31 am
content: The waveform from a VFD through a transformer is not usable. I've tried that. Plus a lot of the common mode noise leaks through.I'd avoid going this way thinking it's cheap.

author: Zero999
author_rank: Super Contributor
timestamp: February 07, 2023, 08:18:51 am
content: Quote from: Jeroen3 on February 07, 2023, 07:05:31 amIsn't that what filters are for?

author: Jeroen3
author_rank: Super Contributor
timestamp: February 07, 2023, 03:06:50 pm
content: Yes, even with two transformer and filters it is still very noisy.