I think I will give that a punt then, thanks for the feedback.
- Thread starter MetalMonkey
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I think I will give that a punt then, thanks for the feedback.
Hopefuldave
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It's expensive... about 50p? Perhaps two quid if you need to buy the parts, more if you don't already have soldering iron, crimpers and a drill
On the ABB ACS300 series the big capacitors (the "DC Bus") are in two pairs, after the 3-phase rectifier the DC in applied across the two pairs in series - inspection of the board will show that one pair has their + terminals going to the soft-start relay (but no need to trace it out), their - terminals connected to the + of the other pair through a large area of copper track, the other pair's - terminals go back to the rectifier (again, no need to trace it!) - there's a bit of space on the copper area where the two pairs come together, that's where the incoming neutral wants to go...
Carefully pick a spot where you can drill a 4mm hole through the board, it needs to have that copper on one or both sides - drill a hole and clean off the green lacquer for 5mm around it, bolt a freshly cleaned and polished m4/4BA *brass* cheesehead screw through then flux (rosin, not acid!) the bolt head (or nut, depending which side has the copper and is more convenient to have the new connection) and board, quickly flow some decent (ideally tin-lead) solder in with a fairly hefty soldering iron to join the bolt and copper. CLEAN UP any bits of copper, PCB dust etc.
That's the hard bit done
On the 3-phase input connector block link the L1 and L3 terminals (this spreads the input current over two sections of the 3-phase rectifier, giving it an easier life), the incoming live will connect to one of these two. Well, both, thanks to the link.
Take the incoming neutral and crimp (and solder if you like to be thorough) a ring terminal on. put a couple of brass m4/4BA nuts on the new terminal post you soldered in and lock 'em together, then washer-ring-terminal-washer-brass nut and lock up tight.
What this does is convert the input stage to a "voltage doubler", with the neutral on the connection between the two banks of capacitors: a positive swing of the mains charges the capacitor with its + end to the rectifier; on the negative swing charges the other bank on its negative terminal - so it now has twice the voltage applied to the capacitor banks. The same units are sold into the US for use on 480v 3-phase, so the voltage isn't way over what they can cope with, only what they'd have in the USA.
As the ACS300 is an old device, it's worth reforming the bus capacitors - I use a variac with a 240v 60W Proper Glowing Bulb in series withthe live wire and slowly bring the voltage up over a few hours (start at about 50v, 10v steps 20 min apart up to 240v works for me) - this limits the inrush current to a maximum of 1/4 amp and allows the insulating layer on the capacitors to re-grow, the bulb will flicker for each increase of volts in but shouldn't glow brightly+steadily, the fan should come on quite early and the soft-start relay can be heard clicking closed, usually about 120v.
Downside: each bank is only charging on half the mains cycle,so there's higher ripple voltage and current, which heats the capacitors more than they're designed for and shortens their life a bit (on the ABB an "UV", under-voltage, alarm will start appearing on heavy load as they get to the end of their lives - £15 ish to replace 'em, same uF, same or higher voltage rating, same or higher ripple current, preferably higher working temperature), and it stresses the rectifier a bit more - my suggestion would be to use the "next size up" of VFD, I use a 5HP VFD for my 3HP motor.
Also... Power factor on the mains isn't great, any warranties expressed or implied, UL and CE approvals etc. will be void (but the ACS300 series are 20+? years old...) and it probably causes Ozone Depletion and Gerbil Warming to boot
This has worked for me on a couple of ACS300 series VFDs, but YMMV as the Septics say!
From what I've seen, the majority of 3-phase 415v input VFDs have the two banks of capacitors, SOME others may be suitable - the deciding factor is probably whether or not they have a "phase loss" disable built in - this can be found out with a look through the fault-finding section of the Friendly Manual for shutdown on loss of a phase, probably?
Dave H. (the other one)
Hopefuldave
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It'd need three connections, + middle and - to two more banks for the voltage doubling to work BUT increasing the capacitance also increases the peak current the rectifier has to cope with, it''d be worth checking the rectifier's datasheet! The rectifier failing short-circuit would be a bit, er... Destructive*?
The added caps would have to be mounted in a box of their own, there's no a lot of space in most VFDs...
Dave H. (the other one)
* e.g. full mains voltage AC across the capacitors, hand grenade / chaff flare impression
So missed out on the 1.5KW one, but managed to pick up an E720S 0.75KW unit for £85 new in the box stamped 2018 so should hopefully still should be a good unit.
https://uk.rs-online.com/web/p/inverter-drives/7457832/ same drive is over £200 on RS so hopefully still a good deal.
Any of you guys with experience know what the difference between the E and D series drives is?
daleyd
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I think the D series lacks a few features of the E series, otherwise they are the same chassis. I think the E series gives a few more advanced options for motor control and you can get things like communication cards for profibus/canbus but nothing that you’d really consider essential for home use.
daleyd
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I think you would struggle to combine them without some major surgery or trickery - if the outputs were out of sync even slightly it would play havoc with the other drive I would have thought. Those are not cheap drives, if 230v they may be worth something to someone for running a small motor like a suds pump or something? If your patient you can get a decent 0.75 or 1 kw drive for not much money.
