EEVblog Electronics Community Forum
Electronics => Projects, Designs, and Technical Stuff => Topic started by: Mukrakiish on December 06, 2017, 02:32:34 pm
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This is a two prong approach to a situation I'm looking at for the place I work. Like many industrial/commercial OEM's you have to cater to the single phase end of things as well as 3-phase. I want to get away from single phase motors and stick to 3-phase. No start windings, no capacitors, no extra mechanical bits. In terms of reliability, if I can remove all single phase motors from my shelf (but still cater to the 230V crowd), I will be a happy man.
My question is, is there a "barebones" VFD/Driver on the market that essentially only packs a handful of features:
- Takes in single phase, convert to 3-phase
- Overload Fault Protection
- Handle from 1/2 HP to 5 HP capacities (should just be a heatsink and internal component sizing at that point?)
- Couple of I/O points to allow for Start/Stop/Reverse/OL Fault
- 220V single phase input, 208 3-phase out
- (Optional) EMC Filter built in
- (Optional) Ramp Up/Ramp Down (soft start, no programmable features)
I've been looking for sometime reputable with a ultra-simplified feature list but had no avail. At this point, I'm ready to build one from scratch if that's what needs to be done. I figured if anyone will know it will be you folks here...I've looked through ACTech, ABB, Siemens, Mitsubishi, etc...but no luck. If there isn't anything terribly cost effective on the market, what are we looking at if I wanted to hire someone smarter than myself to help tackle getting one put together?
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https://youtu.be/uTvUwe2BXGg ?
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Assuming you're in North America based on the voltages?
Are you looking for something basic just to try to keep costs down? I don't think you can do much better bang-for-buck wise than the GS1/GS2 drives sold by Automation Direct, which are simplified siblings of the GS3 Durapulse drives. (I'm sure you can get drives that cost less to buy, but the support and supply chain behind the the drive has to be factored in as well. This is also an important consideration when thinking about rolling your own.) Even the GS1s have more features than you asked for, but you can certainly set them up with basic start/stop controls, ramp up/down, etc. The only part I think you're going to have trouble with is single phase input at >2HP.
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VFDs cost money, it’s as simple as that. Don’t try building your own unless you need many thousand per year. It will take ages and you won’t get good economies or scale. Also, if you pursue the cheapest possible drive you’re probably making some sacrifices on reliability/lifespan.
You may be able to find motors with integrated drives. These are quite easy to deploy and may be a useful option.
On the EMC front, you also need to consider a) fitting EMC filters onto the drives ($) or b) getting drives with filters built in ($) or c) using screened cabling from the drive to the motor ($). It’s $ all round, I’m afraid.
One possibility for getting people to try VFDs is to talk up the soft start, soft stop and variable speed features. These features can really help with the mechanical side of a process (e.g. don’t need dampers, cut down pressure spikes in pipelines).
Please note that almost all VFDs have big DC capacitors inside which will suck down big inrush currents, and most VFDs will generate harmonic currents (especially with single phase supply).
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I design custom VFDs at my job and my advice would be:
- A 400W driver will be very different from a 4kW driver, they should be different products, is not only matter of bigger heatsink, the cost and performance differences are too big to have just one model
- All drivers have some kind of overload protection. Or in case of FOC inverters they don't overload, they just regulate the speed/power to the maximum possible without overload
- Depending on where you live you will be required to have power factor correction on single phase for more than 200W. Even if isn't required, it is very recommendable
- EMC is a world on itself. It isn't as easy as buying a filter (if you want to do it properly) and it depends if you have to comply with an specific EMC standard
- It is VERY different if you just need 10~100 VFDs in total or if you need >1000 per month. If it's the first, just buy something already done, unless you want to learn and you are ready to spend more resources than what those drivers would cost.
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Thanks for all the insight on these...appreciated. It's certainly on the scale of 500+ a year but even then, yes they are going to be a cost. I definitely understand that...after watching a few tear downs I certainly have a new respect for what goes into one as far as controls/brains go. I didn't even think to look into Automation Direct for them, so I will give a couple a try on a trial basis.
@Jbb Agreed, they are costly and for good reason. Certainly you have to know when to draw the line on "too cheap" just buys you headaches in the future which nobody likes.