Replacement inverter advise

[EmgeeParticipant @emgee]

Lot of talk here about Chinese VFD's and the likely use of low cost components that may prove to have a short life.

Is this all assumption because of a much lower cost or has anyone dismantled and checked component suitability in the imported units ?

Certainly not a lot of failures reported on this forum in the last few years, plenty of reports ref poor programming information but most have got things sorted.

Emgee

[old martParticipant @oldmart]

Another reason for my buying a Schneider ATV 12 was the wattage lost to heat at maximum output. The unit is 0.75 kW and runs a 1 hp motor. The waste heat is equivalent to 44 watts which is as good, or better than the competition, the efficiency, hopefully, being the result of design and quality components.

[Nick HughesParticipant @nickhughes97026]

Give NewtonTesla a call, regarding repair of your Mitsubishi inverter.

This link takes you to one of their information pages :- **LINK**

[SillyOldDufferModerator @sillyoldduffer]

Posted by Emgee on 27/12/2019 12:21:26:

Lot of talk here about Chinese VFD's and the likely use of low cost components that may prove to have a short life.

Is this all assumption because of a much lower cost or has anyone dismantled and checked component suitability in the imported units ?

Certainly not a lot of failures reported on this forum in the last few years, plenty of reports ref poor programming information but most have got things sorted.

Emgee

It's a tricky one. First, any modern up-to-date maker of electronic components is likely to be using exactly the same machinery and materials as everyone else. It may be difficult for patriotic Brits and Americans to accept, but Chinese manufacturing can and does perform in the international first division. As does India, Brazil, Mexico, and any other country where it's convenient for investors to set up a factory.

But not everyone is up-to-date. Factories using obsolescent equipment to knock out second class goods (as the British Car Industry did in the 1970s), and new old stock, seconds, and forgeries are all possible. While it's not difficult for an assembler to source decent components and pay for competent designs, its also easy for less respectable types to make a quick buck by knocking out rubbish!

Second, technical improvements aren't always used to improve reliability. Older electronic components (and machines) tend to be sturdily built – oversized, over-engineered, and over-priced. Replaced 1 for 1, the best newer technology always outperforms older. Unfortunately, stuff isn't replaced one for one in the products we buy. Instead, reliability is often exchanged for miniaturisation, running at a higher-temperature, and reduced manufacturing cost. Planned obsolescence is more common than not.

Generally, it can be assumed that sellers of reliable cost-effective gear will survive, whilst over-priced sellers of reliable gear go to the wall as does anyone making gear that is cheap and nasty. It's actually hard to make a living out of tat – too much hassle for low profits!

Twenty years ago it was fairly safe to assume Chinese electronics would be inferior. Absolutely not so today. Once a modern factory has paid off the initial set-up costs, it's remarkable how cheaply it's possible to churn out good products. This is what we are seeing today – the benefits of mass-production coupled with inexpensive labour selling into a global market. But it's NOT safe to assume that everything made in China is wonderful – it's not!

The current generation of budget VFDs bought from a reliable vendor are likely to be competent performers. Not the best available, but good enough to run a home machine without costing a fortune. Imperfections, yes – Robert's comments about missing EMC are all too valid!

I've not dismantled a cheap VFD. Forty years ago I took Japanese electronics apart and found glaring quality issues, today I'd be amazed to find anything wrong. Fifteen years ago, Chinese electronics was often dubious: now the bulk of the world's consumer electronics are Chinese and of good quality. If you want to believe China makes nothing but rubbish, pound shops are your oyster. Otherwise, buy something expensive and prepare for a shock…

What's interesting is who will become the next centre of manufacturing. At the moment China is doing well, but it may be a bubble. Could be we see manufacturing shift somewhere else fairly quickly as the world moves on. Africa and South America are both candidates whilst transport is cheap, but high-fuel costs would shift the advantage back to local manufacture of long-lasting goods again.

Meanwhile, I'd be prepared to try an inexpensive VFD should I ever need one!

Dave

[Clive Brown 1Participant @clivebrown1]

Posted by Mark B on 27/12/2019 11:47:38:

Thanks for all the good information here. The Chinese units are very tempting, but on balance I've decided to go for a branded unit. I chatted to the sales engineer at Inverter Drives Supermarket and they recommended a Schneider ATV12 unit which has known EMC filtering and hopefully better reliability given it costed over 2 times as much.

The documentation installing the unit is also really easy to understand.

I have a Schneider ATV12 unit on a small mill. When first fitted it was unuseable as it tripped the workshop RCD when switched on, and an unprotected circuit wasn't practicable.However, the manual, linked to above, does note that this may be a problem as the built-in EMC filter capacitors allow a leakage current path, (p28). The solution is to remove what's referred to as an IT jumper in the unit. I've done this and all is now well.

The Teco VFD on my Boxford also has an EMC isolating jumper, but it's never tripped the RCD. Likewise my recent Ebay purchase has behaved, but I suspect that this is because it doesn't have a filter to cause problems.

[Anonymous]

Out of idle curiosity I looked up the quoted losses for the VFD I bought to drive the motor on my Pultra lathe. The unit is by Yaskawa and is single phase in, 3-phase 200V out rated at 0.75kW in normal mode. The table gives a heatsink loss of 14.6W and an interior loss of 14.4W. The table quotes a total of 29.1W. That's a shade under 4%, which is pretty good.

Note to SoD: There are many companies in the far East that churn out commodity components in high volume and low price as they haven't had to do the development R&D. They're not companies that sell through distribution. I've been told to shove off because they weren't interested in volumes of 100k per year for a custom transformer, minimum was 100k/month.

Andrew

[Robert Atkinson 2Participant @robertatkinson2]

I've not looked at inside a cheap VFD (the photos are often enough to identify CE non-compliance), but have looked at lots of cheap power supplies. Most of these have lacked EMC components, had unqualified fuses (if any) and worst of all had poor basic electrical safety, for example unsuported solder joints on mains connections, weak cases, inadequate spacing / insulation between mains and low voltage. They "work" but are one failure away from electrocuting someone. VFDs may not have the direct, un-earthed connection to the user of a power supply but can still be dangerous. The Schneider ATV12 looks like a good unit. It might be twice as much, but the difference is less than the cost of filling your car, is it really worth it? I would not entertain a cheap unbranded far eastern VFD personally.

Robert G8RPI.

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