140v voltage regulator - Page 1
Forum section: electronics / projects

author: macona
author_rank: Regular Contributor
timestamp: June 09, 2017, 07:03:19 am
content: So I have a turbo pump that needs 140vdc +/-5% at about 4 amps max for the turbo drive unit. I picked up a power supply that was supposed to be 140v that was intended for servo drives and it turns out it outputs 165v since it is just rectified and filtered line voltage (120v).Any ideas on building a regulator to drop this down to 140v? Or another source of a 140v power supply?-Jerry

author: slurry
author_rank: Regular Contributor
timestamp: June 09, 2017, 07:23:49 am
content: Thats an odd voltage..I would pick three 48V PSU's and connect them in series, but first make sure they can be connected in series

author: macona
author_rank: Regular Contributor
timestamp: June 09, 2017, 08:51:12 am
content: Yeah, really odd and annoying at the same time. So, yeah, 3 48v supplies or 4 36v power supplies. I do have one 48v switcher so it is a toss up. There are also 70v power supplies out there as well.

author: Kjelt
author_rank: Super Contributor
timestamp: June 09, 2017, 09:02:07 am
content: The voltage is not the problem but at 4 Amps we are talking 600+W PSU , that is hugeSo my cheap suggestion would be to add a 6A variac in front of your already bought PSU.It does not have to be isolated and they are second hand cheap to get for $50-70 and you can adjust the AC voltage so the secondary DC voltage is within spec.Most Variacs have a mechanical lock so you can lock it so no-one can accidentally turn the voltage up.

author: calexanian
author_rank: Super Contributor
timestamp: June 10, 2017, 05:14:53 am
content: A variac may be the best solution. 120VDC at 4 amps is a pretty expensive supply. You could go the route of series wireing a few isolated switching supplies but i have no idea how your turbo driver circuit will handle it. Also look for a secondhand turbo power supply. What model are you using? I may be able to dig something up for you as vacuum pumps are a hobby of mine.*Edited* My spec check had changed Varian to Varian. Apt, but incorrect. hahahahaha. Unless its a Varian pump.

author: jbb
author_rank: Super Contributor
timestamp: June 10, 2017, 05:40:31 am
content: If you want a reliable supply, you just buy one. A prebuilt supply will be more reliable than series connection of random supplies.Possible suppliers:Magne PowerAcopianHP/Agilent/Keysight/whatever they're calling it today. Example:N5750A 150V 5ATek, e.g.2260B series(and more...)The 4 questions are:Do you need high quality DC power (e.g. good regulation, low noise, low ripple)?Do you need high reliability?How much does it cost if the supply breaks at exactly the wrong moment?Who's paying for it?

author: NiHaoMike
author_rank: Super Contributor
timestamp: June 10, 2017, 06:51:28 am
content: Perhaps it was meant for the Japanese market, which is 100V (140V rectified) at 50 or 60Hz? Cheaper than a variac would be a transformer connected to buck the voltage, using some light bulbs or similar as a test load.Another solution could be a buck converter. Pretty easy to design and can be made from parts salvaged out of a PC PSU.

author: oldway
author_rank: Super Contributor
timestamp: June 10, 2017, 11:30:14 am
content: What kind of motor has your turbo pump? DC only rectified is enough or must be filtered ?In this case, how many % ripple max ?May be a phase controlled (SCR or triac) power supply could be used ?

author: calexanian
author_rank: Super Contributor
timestamp: June 11, 2017, 02:58:14 am
content: http://mmrc.caltech.edu/Vacuum/Pfeiffer%20Turbo/Turbos.pdfHere is a good PDF on the operation and design of a typical Turbomolecular pump. They are quite remarkable devices. Modern ones are multiphase dc motors. They spin so fast they require high field voltage just as a stepper motor requires higher voltage or lower coil resistance for higher RPM. same principal. The two common deaths of a turbo pump are bearing failure and winding voltage breakdown or power devices in the supply going bang. If something falls into the pump it is much like throwing a brick into a running jet engine. Actually worse. Turbos spin faster.

author: macona
author_rank: Regular Contributor
timestamp: June 13, 2017, 08:16:58 am
content: These pumps come from europe so that kills the 100v idea. They use the same controller on a whole series of pumps. The small pumps run at 24v, next size up is 48, next is 72 and finally the two biggest pumps run off of 140v. The drive detects what pump it is installed on and configures itself for it.I rigged up power to at least test out the turbo, it took some attempts. I have an 80v, 13A sorenson rack mount adjustable supply and another rack mount EDI 60v, 10A supply. Put those two in series and it almost worked. The motor drive on the turbo pulls a lot of current at short bursts and it was causing the sorenson supply to go into current limit mode for some reason. The turbo would only come up to maybe half speed. So I remembered I built and isolated variac dc power supply years ago for anodizing titanium. This almost worked, got it up a little faster then it just starts pulling the voltage causing it to sag, even with a 4.5A variac.So I put them in parallel! Took a little adjustment of the output of the variac PSU and it finally came up to full speed, 40,000 RPM.I found a guy that had a used power supply intended for this turbo on ebay, I just bought it, $165 shipped. I cant mess around at that price trying to piece something together.Funny coincidence on the doc that calexanian posted, the turbo I have is a pfeiffer, one of the 1000l/s units.Turbo pumps can have different kinds of motors, some of the originals had standard induction motors and some sort of gear speed increaser. Modern turbos have either two or three phase motors built into them (Yes, Two phase!). I think the one I have is two phase since the oil pump in the base of the unit runs off two phase. Other pumps like the varian I have in my SEM are three phase.This one had a bad bearing when I got it. It is a hybrid unit where it uses a permanent magnet bearing on top and a ceramic ball on the ball. I was very lucky that the bearing was a pretty standard sized bearing and was able to get a replacement from a bearing supplier that specialized in ceramic bearings. The original bearing had a special ball cage that funneled oil up into the bearing and I was able to just pop it on the new bearing. The oil for the pump is insanely expensive. 40ml is something like $180 and it needs 65ml.Video of the pump with the bad bearing.I have a bunch of other turbos from little 50l/s at 72krpm that I have on my RGA and carbon coater to the big 2000l/s unit I have on my large vacuum system. It runs on mag lev bearing at 27krpm.

author: calexanian
author_rank: Super Contributor
timestamp: June 13, 2017, 10:03:18 pm
content: They are not meant to be operated at atmospheric pressure like that. Test it in a vacuum with a proper backing pump. You may have buggered it already.

author: macona
author_rank: Regular Contributor
timestamp: June 14, 2017, 03:41:48 am
content: Modern turbos can be started at atmosphere, in fact in the manuals they mention when using a turbo with a direct connection to the chamber you can start the roughing pump and the turbo at the same time. The motor has current limiting so it will never come anywhere close to a fraction of full speed. Older turbos had stamped vanes and overly powerful motors that can be damaged by the flexing of the rotor discs and crashing them into the stator.

author: calexanian
author_rank: Super Contributor
timestamp: June 15, 2017, 06:54:33 pm
content: What a world we live in!