EEVblog #814 - Keysight N8762A 600V 5100W PSU Teardown - Page 1
Forum section: electronics / general

author: EEVblog
author_rank: Unknown
timestamp: November 06, 2015, 10:07:08 pm
content: A look inside a dumpster Keysight/Agilent N8762A 600V 8A System DC power supply.Where did the magic smoke escape from?PCB spark gap video:

author: gerrysweeney
author_rank: Regular Contributor
timestamp: November 06, 2015, 11:10:18 pm
content: Dave,Not sure how you would feed your single phase supply into "All three phases" as you stated because in three-phase there is no "common", what you would need to do is feed your single phase supply into L1 and L2 (or L2 and L3, or L1 and L3), any combination should work fine.Gerry

author: c4757p
author_rank: Super Contributor
timestamp: November 06, 2015, 11:13:34 pm
content: I do hope he didn't have the fourth (earth) terminal in mind when he said that.

author: EEVblog
author_rank: Unknown
timestamp: November 06, 2015, 11:33:20 pm
content: Quote from: gerrysweeney on November 06, 2015, 11:10:18 pmYes, correct. I should have looked and thought harder before blabbing. Yes this is not a common earth supply, so have to hook up one phase to 240V only.The earth is only a safety earth.This has already been corrected on the annotation.

author: EEVblog
author_rank: Unknown
timestamp: November 06, 2015, 11:40:50 pm
content: Actually, come to think of it, the small three phase wires (near the MOV's) going over to the smaller PSU board looks suspicious. No reason to do that really unless that board is doing some sort of phase presence detection. In that case I'm likely out of luck and the thing won't power up with a single phase hooked up. Murphy might ensure that.

author: Yansi
author_rank: Super Contributor
timestamp: November 06, 2015, 11:59:28 pm
content: The phase-loss detection(protection) circuit is quite probable to be there. It does make sense, because if losing one of the phases, you will overload the remaining powered part of the three-phase bridge rectifier.

author: Phoenix
author_rank: Frequent Contributor
timestamp: November 06, 2015, 11:59:59 pm
content: Quote from: EEVblog on November 06, 2015, 11:40:50 pmI've seen similar (Magna Power) units with phase loss detection, these things would be pretty smart inside.What you might find is that the big relays only close once the system is up and running and you've enabled the power output; and that the power circuitry and those big capacitors havn't been stressed at all. Only need to follow that low power/signal path with the blown MOV, input bridge rectifier and whatever that goes to.

author: RobB
author_rank: Contributor
timestamp: November 07, 2015, 12:10:29 am
content: Take a good look at the remaining Fuse specs Dave. Being a switcher it will probably require a set of fast blow fuses.Apologies if this is a grandma and egg tale.

author: MartinX
author_rank: Regular Contributor
timestamp: November 07, 2015, 12:15:33 am
content: Some three phase supplies like that can be fed by a single phase, you would have to look in the manual so see if it is possible. A certain input would have to be used like L1-L2 and some dip switch or jumper be set in the correct position, I have come across some Sorensen supplies like that. As I understand it in the US there are single phase 120-0-120 outlets that can deliver much more than 10A.

author: crispy_tofu
author_rank: Super Contributor
timestamp: November 07, 2015, 01:56:23 am
content: Hehe, you have 247V in the lab, I have 250V!(probably because I live close to a substation)According tothis document, the absolute maximum in NSW is 264V, with a notification for adjustment at 253V.

author: EEVblog
author_rank: Unknown
timestamp: November 07, 2015, 02:14:04 am
content: Quote from: MartinX on November 07, 2015, 12:15:33 amYes, good read of the manual required first.

author: gardner
author_rank: Regular Contributor
timestamp: November 07, 2015, 02:42:41 am
content: There are many VFDs available that are designed to run three-phase industrial equipment (pumps, saws, mills etc) from single/split phase supplies. I believe you will find something from China that is designed for 120V that can generate three-phase 208V at 0-300Hz for $150 or so.Edit:Here's a nice one:http://www.ebay.ca/itm/110V-3KW-4HP-13A-VARIABLE-FREQUENCY-DRIVE-INVERTER-VFD-HY-FOR-CNC-SPEED-CONTROL-/281385471151?hash=item4183e18caf:g:cwQAAOSwsB9WAAB2

author: rs20
author_rank: Super Contributor
timestamp: November 07, 2015, 02:56:27 am
content: Quote from: gardner on November 07, 2015, 02:42:41 amI was thinking of suggesting the same thing; but do these VFDs output something close enough to a sine wave for the PSU to consider acceptable? These VFDs often assume an inductive load, right?

author: ro_ss
author_rank: Newbie
timestamp: November 07, 2015, 03:27:28 am
content: I would assume that the rest of the PSU is fine owing to the relays.I'd say that they plugged in the PSU with the switch off thus the relays would be off and no power is applied to the PFC board and the rest of the PSU wouldn't have been damaged hence there isn't any damage visible.

author: maor
author_rank: Contributor
timestamp: November 07, 2015, 05:30:47 am
content: So I was going through tdk-lambadas promotional video and guess what I saw?

author: crispy_tofu
author_rank: Super Contributor
timestamp: November 07, 2015, 05:37:29 am
content: Link?

author: Huluvu
author_rank: Regular Contributor
timestamp: November 07, 2015, 05:57:23 am
content: Dave - I assume the mentioned gluing at 9:30 is defined by the result of S&V Test.The glue will be placed on the components where the resonant testing showing any weakness.Rgds

author: bktemp
author_rank: Super Contributor
timestamp: November 07, 2015, 06:47:24 am
content: Quote from: Phoenix on November 06, 2015, 11:59:59 pmI was thinking the same when watching the video.If Dave is lucky, the MOV or some other low power stuff blew/shorted before the two big relais enabled the high power stuff.If there are no shorts at the DC rail going into the PFC, then all the high power stuff is most likely fine.Why is there a spark gap on the pcb under the common mode choke at the output? I have seen this on many common mode chokes. Does anybody know?

author: maor
author_rank: Contributor
timestamp: November 07, 2015, 06:56:20 am
content: Quote from: crispy_tofu on November 07, 2015, 05:37:29 amit's in hebrew...http://www.tdk-lambda.co.il/about/local-video.aspx?pid=495

author: Arjan Emm
author_rank: Regular Contributor
timestamp: November 07, 2015, 08:04:15 am
content: This power supply looks very similar to the genesys 2U series from TDK Lambda.http://uk.tdk-lambda.com/products/product-details.aspx?cid=3&scid=273

author: EEVblog
author_rank: Unknown
timestamp: November 07, 2015, 08:49:08 am
content: Quote from: Huluvu on November 07, 2015, 05:57:23 amCould be, but the exact same leaded parts don't have it elsewhere, so if so it wouldn't be (or shouldn't) because of an actual leaded component modal reason. So could be a PCB modal component involved. But I suspect the reason for the stuff is not nearly this complicated.

author: EEVblog
author_rank: Unknown
timestamp: November 07, 2015, 08:49:51 am
content: Quote from: Arjan Emm on November 07, 2015, 08:04:15 amLooks the same!Schematics for that one I wonder?

author: EEVblog
author_rank: Unknown
timestamp: November 07, 2015, 08:51:18 am
content: Quote from: ro_ss on November 07, 2015, 03:27:28 amCould very well be. And welcome to the forum!

author: Huluvu
author_rank: Regular Contributor
timestamp: November 07, 2015, 09:03:44 am
content: Quote from: EEVblog on November 07, 2015, 08:49:08 amI know from our resonant testing lab that they put the whole unit on the shaker and vibrate it according special standards/requirements.You always have some special resonant areas where the board or components became oscillating. (that's why they put glue on it)Another reason might be some safety issue if the component get loosen.

author: station240
author_rank: Unknown
timestamp: November 07, 2015, 09:26:50 am
content: L1 Fuse blownL2 MOV blownL3 Fuse BlownSeems to be some sort of pattern here.Both fuses blew instantly, the remaining Line was then shorted to earth by the MOV.Never seen a ceramic fuse blow hard enough for the magic white dust to escape from inside.I'd advise caution with using it over single phase.As 5,100W over 240V is 22Amps, and the start up current could be higher, after all it does have 32 Amp fuses on all 3 phases (well did have).The phase detection can be outwitted with this circuit, on the low voltage side of the sense resistors.http://www.homemade-circuits.com/2013/09/three-phase-signal-generator-circuit.html

author: Phoenix
author_rank: Frequent Contributor
timestamp: November 07, 2015, 09:34:08 am
content: Quote from: Huluvu on November 07, 2015, 09:03:44 amThere is a standard (can't remember which) that says if a component is close to the chassis and can be pushed to make contact with the chassis using 10N it's unsafe - the capacitor on the input board would need glue to pass this... but the chassis appears to have a layer of plastic on the inside.Are the extra wires in the CT's some sort of self test?

author: Arjan Emm
author_rank: Regular Contributor
timestamp: November 07, 2015, 09:46:36 am
content: Quote from: EEVblog on November 07, 2015, 08:49:51 amOn first glance the usermanual doesn't seem to mention an option to use only 2 phases. It can produce an ac fail error. I can't find the specifics of that error. But that error could come up if one of the phases is missing. If, after replacement of the fuses and mov this error comes up, this could be an indication that unit is working fine but needs it's 3rd phase.The manual does state that there are 2 versions, 240 en 400v. This one is clearly for the american market.

author: VK3DRB
author_rank: Super Contributor
timestamp: November 07, 2015, 10:45:36 am
content: Dave, a good tear down.Australia is NOT a 240V country. It is a 230V country.Vic and NSW still run 240V as nominal, but Australia as a country is officially classed as a 230V nominal voltage country. In any case, 247 V is nowhere near the "extreme limit of what is allow here". The limit is264Vin Vic and NSW. I get 255 volts here at the fuse box here but it is well within the maximum limit here in Victoria.The reason for this power supply blowing up reminded me of a colleague at IBM who was electronically as thick as a brick. He plugged our mains into a 110V machine imported from the USA, blowing the crap out of it. He had checked the voltage on the machine but thought we had 110V in our mains and the Americans has 240V. It turns out he was a lemon because he had no idea whatsoever about basic electrical safety or anything he was hired to do. I believe he faked his qualifications and his experience. Some months after he joined the company, he was fired and literally marched to the door. A big lesson learnt.I bought one of these Agilent power supplies before. 60V max, and very high current. It was badge engineered from TDK-Lambda, as I suspect this power supply you reviewed is. In fact you could buy pretty much the same power supply under different brand name. A terrific power supply, but mine only had the huge screw terminals at the back. For lower current applications, they could have furnished a few banana sockets, cutting of the output at these sockets at say 10A via a relay. It was programmable, so it was used to stress test designs and for general R & D use.It is annoying not having intelligent labels on connectors etc, but they don't want anyone in the general public to mess around with the insides. I noticed a few small devices have their top over lay white ink cut off by vias. Time pressure on the PCB layout bloke maybe, but usually it is just plain laziness. Their component libraries are not consistent either. The fly vomit pin 1 markers on IC's for same package pin spacing have different sizes. (Triangles are a much better pin 1 markers than fly vomit). Plus some components have their designators inside a box, others do not. I can only guess this is because they have no component library standards. This is not what I would call PCB artwork. It is clearly not Hewlett Packard quality from the days when it was a test equipment company.

author: bigsky
author_rank: Regular Contributor
timestamp: November 07, 2015, 10:53:33 am
content: We'd all love to see this beast repaired. If you are very lucky, it may just be the fuses and MOV that blew. Next would be the input bridge rectifiers.I found the manual here:http://www.matsolutions.com/Portals/0/Product%20documents/Agilent%20Technologies/N8736A/N8736A%20User's%20Guide.pdfI can't see any mention of missing phase detection so it may be OK running it from a single phase supply across two of the input terminals.The manual says (page 95) that the input range is 170-265 Vac for this version, so it should be OK off your somewhat high mains supply.It wouldn't be too difficult to get a proper 120/208v three phase supply if needed. There are many ways of doing this.If you can get a 3 phase 240/415v supply (which I'm sure your building will have), this could be stepped down. A three phase transformer might be a bit hard to find, but you could do it with three identical 240-120v single phase transformers. For testing purposes they could be small ones. You could also use 6 transformers and go via an intermediate voltage (eg 240-12-120v).If getting access to three phases is awkward, then the VSD approach suggested by gardner might work. Or a small motor/alternator set. Or some sort of static converter. It's a common problem faced by people who need to run three phase motors from single phase supplies, and there are plenty of solutions.

author: bigsky
author_rank: Regular Contributor
timestamp: November 07, 2015, 11:12:15 am
content: Quote from: station240 on November 07, 2015, 09:26:50 amI think the MOVs will be delta connected, across the phases. I wonder if the MOV that blew took out the fuses on the phases feeding it.QuoteI don't think you realise that the AC current draw will depend on the load connected to the DC side. With no load I can't imagine it would take more than 0.5A per phase. Obviously its full capacity will not be possible from a single phase supply (assuming it will run from one) but that's not relevant to a repair.

author: EEVblog
author_rank: Unknown
timestamp: November 07, 2015, 11:23:09 am
content: Quote from: VK3DRB on November 07, 2015, 10:45:36 amI know. I still call it 240V.

author: EEVblog
author_rank: Unknown
timestamp: November 07, 2015, 11:24:43 am
content: Quote from: station240 on November 07, 2015, 09:26:50 amNot unless you were silly enough to fully load it during repair

author: Monkeh
author_rank: Super Contributor
timestamp: November 07, 2015, 11:30:58 am
content: Quote from: bigsky on November 07, 2015, 11:12:15 amBut there may be little or no inrush current limiting.

author: LINACboy
author_rank: Contributor
timestamp: November 07, 2015, 11:35:10 am
content: Spot the difference!This is was taken from a TDK-Lambda GEN300-17:Same series, but 300V/17A and with proper 3~/400V input.That Agilent unit is a complete rebadger.

author: Arjan Emm
author_rank: Regular Contributor
timestamp: November 07, 2015, 11:37:24 am
content: Just turn the voltage up using a variac. No inrush problems..

author: Spamlobster
author_rank: Newbie
timestamp: November 07, 2015, 11:41:29 am
content: Quote from: EEVblog on November 07, 2015, 08:49:08 amI think it's just additional mechanical support to prevent twisting them when you're operating heavy machinery (ie fingers) around them. I keep noticing something that requires handling near those glued caps, such as the fuses, pin headers/connectors, screwed on cables, the output board you need to semi-blindly mount upside down...

author: TheAmmoniacal
author_rank: Unknown
timestamp: November 07, 2015, 12:06:56 pm
content: Of course the Agilent is a rebadger, but that's not a problem as long as they rebadge from the best.I also found a technical manual (no schematics unfortunately) for the Genesys U2 5kW from TDK-Lamda which looks identical:https://dl.dropboxusercontent.com/u/15526481/docs/83515000.pdf

author: rs20
author_rank: Super Contributor
timestamp: November 07, 2015, 12:11:21 pm
content: Quote from: LINACboy on November 07, 2015, 11:35:10 amNo ethernet interface on that one?

author: TheAmmoniacal
author_rank: Unknown
timestamp: November 07, 2015, 12:17:12 pm
content: What are the financial incentives to rebadging this stuff? Agilent buys 1000 units for 30% off to make 30% profits?

author: PChi
author_rank: Frequent Contributor
timestamp: November 07, 2015, 12:25:52 pm
content: I have had large electrolytic capacitors make a disconcerting click when they break down inside and blow the fuses leaving no external evidence. They may work OK with some performance loss after the event but can't be trusted in the long term.

author: Yansi
author_rank: Super Contributor
timestamp: November 07, 2015, 12:56:28 pm
content: Quote from: gardner on November 07, 2015, 02:42:41 amPretty stupid and dangerous suggestion. Don't fall for that!VFD's must be NEVER EVER used as a single to three phase voltage converters. Unless you know hell of a lot what you are doing. In the VFD there is absolutely NO output voltage ripple filtering, the output is pure square pulse output, as the current is being smoothed by the motor winidng inductance. Depending on the modulation scheme and control algorithms, the VFD can (or most times cannot) be modified with external LC filters to function as a one-to-3-phase converter to supply other equipment, than plain 3ph motors.

author: LINACboy
author_rank: Contributor
timestamp: November 07, 2015, 01:44:59 pm
content: Quote from: TheAmmoniacal on November 07, 2015, 12:17:12 pmI'd assume, the customer will always have to pay extra for the Agilent badge - even if Agilent themselves might get bulk discounts. So the only scenario where it might make sense to buy these devices would be when Agilent won a tendering for some kind of turn-key plant where the contract states that they are responsible to provide maintenance services for all sub-systems - general contractor style.

author: gardner
author_rank: Regular Contributor
timestamp: November 07, 2015, 04:01:07 pm
content: Quote from: Yansi on November 07, 2015, 12:56:28 pmIn cheap VFDs that will be the case, yes. The output waveform is comparable to what you see from a "modified sine wave" inverter. It sucks.But you'll have to clarify in what way this is "dangerous" or inappropriate to testing a piece of gear that requires three phase. It would undoubtedly be inefficient, and would likely confuse the hell out of the PFC. Where is "danger" or "stupid"?

author: Lukas
author_rank: Frequent Contributor
timestamp: November 07, 2015, 04:46:24 pm
content: Quote from: LINACboy on November 07, 2015, 11:35:10 amLooks like Agilent rolled their own I/O (LAN, etc) board. See alsohttps://www.eevblog.com/forum/testgear/agilent-n5772a-600v-2-6a-1560w-power-supply-teardown/

author: LINACboy
author_rank: Contributor
timestamp: November 07, 2015, 05:45:45 pm
content: Quote from: gardner on November 07, 2015, 04:01:07 pmYour're both right. A proper motor VFD produces a PWM sine voltage at its output. It is designed for inductive loads. In fact, it needs the motor inductance to low-pass filter the output current. Because of this, each phase winding is subjected to the modulated square voltage from the VFD. The harmonic content is what increases voltage stress in the motor insulation compared to a mains driven motor and why VFD operated motors require better quality magnet wire for the same life expectancy.Unlike a motor, the DC-PSU is a resistive load. Simple solution: Add a couple of series inductors between VFD and PSU to make it appear more inductive. However, this will only work for steady state operation of the PSU. Load transients could excite oscillations between the filter inductors and the DC link capacitors. Controlling those requires careful design.Single phase operation (with a variac for inrush current limitation!) is the way to go for testing, provided that phase-loss detection, active PFC or any other active input circuitry won't protest.

author: Fungus
author_rank: Super Contributor
timestamp: November 07, 2015, 05:53:49 pm
content: Quote from: TheAmmoniacal on November 07, 2015, 12:17:12 pmIt works out to be more than 30% because they have no R&D costs for this unit. Building their own might need them to open more offices, look for more engineers, etc.Plus: It's a good way to test the water for a new line of products and find out how well they sell. They can build their own units later on if it makes financial sense to do so.If it means one more "Agilent" badge in a lab then that's good, too.There's lots of good business reasons if you think about it.

author: Len
author_rank: Frequent Contributor
timestamp: November 07, 2015, 06:11:55 pm
content: Quote from: TheAmmoniacal on November 07, 2015, 12:17:12 pmTo fill in a gap in their product line, so their customers aren't tempted to look at another company's catalog.

author: ConKbot
author_rank: Super Contributor
timestamp: November 07, 2015, 06:22:28 pm
content: I'd actually like to see a davecad™ of the PFC section. I get how single phase active PFC works, but 3 phase wouldnt play so nice with the simple "plop a boost converter after the rectifier" type used in single phase supplies. I'm seeing a few different typologies online, and I'm curious as to what someone like TDK lambda would use.

author: firewalker
author_rank: Super Contributor
timestamp: November 07, 2015, 07:18:52 pm
content: Why 3 bridge rectifiers?Alexander.

author: Monkeh
author_rank: Super Contributor
timestamp: November 07, 2015, 08:17:06 pm
content: Quote from: firewalker on November 07, 2015, 07:18:52 pmBecause it's 3-phase?

author: bktemp
author_rank: Super Contributor
timestamp: November 07, 2015, 08:45:02 pm
content: Quote from: Monkeh on November 07, 2015, 08:17:06 pm3 phase input has 3 wires. 3x bridge rectifiers have 6 inputs. For a 3-phase bridge rectifier only 6 diodes are needed, but her are 3x 4 diodes used.It would be interesting to know what the difference between the 208V and the 400V version is. The rectifier sections looks totally different on the 400V version.I had expected 3 PFC circuits, but it looks like only 1 unit is fed by the rectified output from all 3 phases. I have know idea how this can work.

author: Monkeh
author_rank: Super Contributor
timestamp: November 07, 2015, 09:32:28 pm
content: Quote from: bktemp on November 07, 2015, 08:45:02 pmBecause purpose built bridge rectifiers are cheap, durable, easily heatsinked, and in stock in huge quantities. It's entirely normal.

author: Yansi
author_rank: Super Contributor
timestamp: November 07, 2015, 10:14:15 pm
content: You just connect the ~ pins together and get a double diode in one easily heatsinkable package. Then take three of these and make cheap 3f bridge.

author: bigsky
author_rank: Regular Contributor
timestamp: November 07, 2015, 10:48:53 pm
content: Quote from: Monkeh on November 07, 2015, 09:32:28 pmAnd you can use the same part for both single phase and three phase boards, which has many benefits.

author: station240
author_rank: Unknown
timestamp: November 07, 2015, 11:12:11 pm
content: Technically you only need 1.5 (eg 2) bridge rectifiers as you have 2 inputs per package.However as the did the output stage with 2 parallel diodes (another bridge rectifier), then no reason not to do the same with the input.Alternative is 3 twin diode packages, with the correct A-KA-K (common A and K), which is available as IGBT bricks, and I suspect smaller packages as well.

author: German_EE
author_rank: Super Contributor
timestamp: November 08, 2015, 12:10:01 am
content: For all young players (and those not used to three-phase electrical circuits) the correct terminology here is either wye-delta or star deltahttps://en.wikipedia.org/wiki/Three-phase_electric_powerWhat Dave has is a delta three phase unit with three live connections and no neutral (not very common in an office or home environment). The normal way of doing things is the wye or star circuit where there are three live connections PLUS a neutral lead.I have seen delta wired units that have been brought to life on a single phase supply by connecting live to L1, neutral to L2 and a motor start capacitor between L1 and L3 but this was an inductive load and not a piece of electronic equipment. A certain amount of care needs to be taken here or the magic smoke may escape again.

author: Phoenix
author_rank: Frequent Contributor
timestamp: November 08, 2015, 01:58:13 am
content: Quote from: ConKbot on November 07, 2015, 06:22:28 pmI'm quite curious too. I can spot 2 magnetics that look like they might be 2 PFC inductors... Can't find a topology that fits for that though.

author: max666
author_rank: Frequent Contributor
timestamp: November 08, 2015, 03:52:41 am
content: Quote from: German_EE on November 08, 2015, 12:10:01 amI'm not claiming to know enough about Three-phase power to make a statement here, but how can you distinguish whether Dave has a star or delta unit? The neutral in a star configuration is optional, so the 3 bridge rectifiers could be wired in a delta as well as star configuration, can they not?And I venture the motor start capacitor method would be even more dangerous than the suggested VFD method. The capacitance needed for a motor start capacitor is dependent on the inductance of the winding and in turn of the loading, so I guess depending on what the electronic load does you could even get over-voltage at the input by connecting a motor start capacitor.And since a lot of people are wondering how the PFC is done, and again I'm just talking out of my ass here, but if I'm not mistaken for single phase PFC you have to make sure that your current draw looks like this:so I would say all you have to do for three-phase rectifiers, is make sure the current draw after them looks like this:

author: rs20
author_rank: Super Contributor
timestamp: November 08, 2015, 05:03:47 am
content: Quote from: max666 on November 08, 2015, 03:52:41 amIncorrect, the three phase rectifier will always draw all current from the phase with the highest instantaneous voltage; which means a naive implementation of PFC after a three-phase rectifier will draw dramatically non-sinusoidal currents from each phase. Example:Here we see a Y input going through a three-way rectifier, and then into R1, which is perfectly phase-correct by virtue of being a resistor (put another way, it implements your suggestion of keeping current in proportion to voltage). As you can see, the current waveform (red) is dramatically non-sinusoidal, as compared to the corresponding phase voltage waveform (green).EDIT: Fixed broken image link.

author: Phoenix
author_rank: Frequent Contributor
timestamp: November 08, 2015, 05:07:52 am
content: Quote from: max666 on November 08, 2015, 03:52:41 amNot very sinusoidal once you unravel it, but yes that would be the simplest method and only requires a single inductor (video appears to have 2 inductors).There are many better topologies, check out this guys lit review:http://scholar.lib.vt.edu/theses/available/etd-08142002-075617/unrestricted/Barbosa_ETD.pdfSomething like Fig. 1-6 is feasible for the Agilent unit as it has 2 inductors (visible in Dave's video at 13:06) and a whole bunch of to220 t0247's on those heatsinks labelled P 200 5k.Some more good material:https://www.pes.ee.ethz.ch/uploads/tx_ethstudies/Kolar_Essence_Three-Phase_PFC_02.pdfhttps://www.pes.ee.ethz.ch/uploads/tx_ethpublications/08_Towards_a_99__Efficient_ThreePhase.pdf

author: bktemp
author_rank: Super Contributor
timestamp: November 08, 2015, 06:36:43 am
content: Quote from: Phoenix on November 08, 2015, 05:07:52 amI can see only 2 thick wires between the rectifier board and the PFC, so they are using either the simple PFC with 2 channels interleaved in parallel, or they are using some other clever circuit, but I can not see how this could work without a connection to each phase.

author: rs20
author_rank: Super Contributor
timestamp: November 08, 2015, 07:01:33 am
content: Quote from: Phoenix on November 08, 2015, 05:07:52 amWhat? No, it's not a viable method at all, asI've already demonstrated...

author: alxpo
author_rank: Contributor
timestamp: November 08, 2015, 08:37:49 am
content: Quote from: max666 on November 08, 2015, 03:52:41 amThere is more funny way to provide 3 phases for testing - connect 3-phase motor with appropriate phase-shift capacitor in parallel to PSU. Sure, power of motor should be bigger than idle power of PSU and power of test load (I suppose quite small test load).

author: German_EE
author_rank: Super Contributor
timestamp: November 08, 2015, 10:20:43 am
content: As I said, the only time I have seen the start capacitor trick used was on an inductive load (which was of course an electric motor) although I do not recall how the value of the capacitor was worked out as this took place over thirty years ago. As for the Wye including a neutral connection, it is of course possible to connect a three-phase motor in Wye configuration and ignore the neutral center tap but all Wye supplies that I have seen include a neutral return.Connecting this unit in Dave's lab environment could be a problem.

author: drago
author_rank: Contributor
timestamp: November 08, 2015, 11:22:04 am
content: I bet Dave has 3 phases distributed in his lab across different points of load. Extension cords and little bit of fiddling could do the job

author: Monkeh
author_rank: Super Contributor
timestamp: November 08, 2015, 12:57:02 pm
content: Quote from: drago on November 08, 2015, 11:22:04 amI doubt it, it's a total waste of wire and effort running multiple phases to a small office like that.

author: max666
author_rank: Frequent Contributor
timestamp: November 08, 2015, 01:07:28 pm
content: Quote from: rs20 on November 08, 2015, 05:03:47 amAhh yes, I can see now where my naive picture went wrong. Thanks for the simulationBut I have to say, compared to a rectifier going straight into bulk capacitance, the above PF doesn't look that shabby to me. I guess around 0.85 maybe?Can LTspice calculate the PF? Otherwise I'll see if I can take a shot at it, after I get some sleep.Edit: I really should go to sleep. My sleepy state math gets me a PF of 0.83

author: SeanB
author_rank: Super Contributor
timestamp: November 08, 2015, 02:07:39 pm
content: Quote from: Monkeh on November 08, 2015, 12:57:02 pmDistribution board for the floor, or the group of offices, would be 3 phase. The offices might have it supplied, as you can get by with a cheaper thinner cable, you need a 16mm cable and neutral for a 60A single phase supply, but for a 30A 3 phase supply you can get by with 4mm cable, around half the copper. The power delivered is the same, but spread out over 3 conductors, and the neutral only has to handle the imbalance and harmonics. Thinner cable is easier to work, as you can fit it in standard 25mm conduit as well, you do not need to have a 50mm conduit and a termination at the top in the duct.

author: Monkeh
author_rank: Super Contributor
timestamp: November 08, 2015, 02:16:07 pm
content: Quote from: SeanB on November 08, 2015, 02:07:39 pmI doubt he has a 60A supply, you don't need necessarily need 16mm² for 60A, and the cost of a three-phase board and the breakers is likely greater than the cost of the cable.You also then have to take into account the presence of multiple phases in an environment occupied by people with no concept of them.

author: k2teknik
author_rank: Regular Contributor
timestamp: November 08, 2015, 02:57:19 pm
content: Quote from: Monkeh on November 08, 2015, 02:16:07 pmWell these kind of stuff is Country specific, very Country specific, no need to claim that on is better, or more right than the other.These thing is also regulated by local law, which also differ from Country to Country, again it do not give any sense to discus what is right/best, just be aware that this stuff differ from location to location.

author: SeanB
author_rank: Super Contributor
timestamp: November 08, 2015, 03:03:36 pm
content: You only need a 3 phase incoming isolator, all others are single phase in a small office. 3 phase is good as you might want an aircon of more than 30 000 BTU which is almost invariably a 3 phase unit. Even allowing for a 10mm cable you have 20mm of copper, and a PE of 6mm, as opposed to the 3 phase one being 16mm of copper and a PE of 2.5mm. The internal wiring to the outlets and lighting plugs will still be 2.5mm and 1.5mm respectively.This applies to South Africa, it is very similar in Australia for cable size, as this is dictated by allowable temperature rise in the cable when installed either bare in plaster, in conduit or in free air in a cable way in the building.

author: Monkeh
author_rank: Super Contributor
timestamp: November 08, 2015, 03:07:01 pm
content: Quote from: SeanB on November 08, 2015, 03:03:36 pmYou still need a 3-phase board. 3-phase MCBs are no more expensive than single-phase (they are in fact the same MCB with a slightly different case and a link), however going to a 3-phase system requires DIFFERENT MCBs (even single-phase) than a single-phase board, as you have phase-to-phase fault currents. Those are more expensive.

author: madires
author_rank: Super Contributor
timestamp: November 08, 2015, 03:19:45 pm
content: Quote from: max666 on November 08, 2015, 03:52:41 amNot quite! In a star / Y configuration neutral is only optional (electrically, local sparky code might say something else) when all phases are loaded identically, e.g. by a 3 phase motor. The PSU has two power modules for the output and a third one for internal power. Hence it has to be in delta configuration without a neutral terminal. Also the rating of the input voltage suggests this.

author: Towger
author_rank: Super Contributor
timestamp: November 08, 2015, 04:06:48 pm
content: I also think Dave may have 3 phase to the panel. But you are forgetting that the power supply is for puny yankee 3 phase, which is why it originally had the arse blown out of it.Dave would still need to step down the voltage and in any case the Australian rules do not allow Dave to work on the mains, as he does not have the required paperwork. ..

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: November 08, 2015, 04:31:35 pm
content: Hi,If this unit was on my bench I would figure out where the auxiliary supply is connected. It has to be connected between one pair of lines, L1-L2, L1-L3 or L2-L3.The auxiliary supply is required to start the unit. It is probably the small line frequency transformer on the Input board. I would check it first. It could be damaged by being connected to 400V.I would then run the supply at low power, less than 100W, using two phases. This assuming the power supply is not smart enough to detect a missing phase. If it is I would try and defeat that circuit.I don't believe that schematics are available for this unit.I have added some more photographs to this thread:https://www.eevblog.com/forum/testgear/agilent-n5772a-600v-2-6a-1560w-power-supply-teardown/msg795977/#msg795977Showing pictures of the boards in the single-phase, lower power, version N577x family.Regards,Jay_Diddy_B

author: AF6LJ
author_rank: Unknown
timestamp: November 08, 2015, 05:06:45 pm
content: Good Video..

author: boffin
author_rank: Unknown
timestamp: November 08, 2015, 08:22:01 pm
content: Quote from: Monkeh on November 08, 2015, 12:57:02 pmIn north American pretty much any building of more than about 1000 sqm would be three phase, so it wouldn't surprise me at all if Dave has 3 phase in his office, and dead easy to check.Go to the main breaker and if it's a triple main breaker with breakers labeled ABCABCABC down the side it's three phase. Each 'normal' circuit is one phase to Neutral.Most houses are 2 phase 180 (at least in North America), double main breaker, and breakers labeled ABABABAB

author: station240
author_rank: Unknown
timestamp: November 09, 2015, 09:10:54 am
content: It's been stated in several videos, The Lab does not have 3 phase, it's just a small breaker box on the wall. To get 3 phase would mean running a new cable downstairs to the main meterbox.

author: Monkeh
author_rank: Super Contributor
timestamp: November 09, 2015, 01:46:27 pm
content: Quote from: boffin on November 08, 2015, 08:22:01 pmNorth America is not ROW.Pretty much everyone else does things differently. And most of us do things much the same way.

author: Wolfram
author_rank: Frequent Contributor
timestamp: November 09, 2015, 04:08:51 pm
content: Quote from: max666 on November 08, 2015, 01:07:28 pmPower factor is actually above 0.95, so it is not a bad solution at all. The first harmonic current is the fifth, at an amplitude of a fifth of the fundamental current. It's a commonly used configuration, being significantly simpler and cheaper than a full 3 phase active PFC, while having very good power factor. One major advantage is that a simple off-the-shelf single-phase PFC controller can be used.

author: max666
author_rank: Frequent Contributor
timestamp: November 09, 2015, 11:07:24 pm
content: Ah yes, thank you for correcting me, I should have just gone to bed.Silly me calculated it by doing Fourier sine and cosine series and then managed to include both the sine and cosine series coefficients into the PF calculationOf course much quicker would have been to calculate it with PF = |P|/S ... meh.With both methods I now get PF = 0.95577Edit:Quote from: Wolfram on November 09, 2015, 04:08:51 pmSo a low pass filter would be simple and effective, wouldn't it?

author: M4trix
author_rank: Frequent Contributor
timestamp: November 09, 2015, 11:28:30 pm
content: That's why I never liked maths. They say, gifted mathematicians are prone to schizophrenia!

author: max666
author_rank: Frequent Contributor
timestamp: November 10, 2015, 12:02:43 am
content: Me and myself can't agree to that, we both love maths

author: Phoenix
author_rank: Frequent Contributor
timestamp: November 10, 2015, 09:15:56 am
content: Quote from: max666 on November 09, 2015, 11:07:24 pmWould need a ginormous L and C to get the cutoff frequency into the baesbands. However, the PFC's have an LC filter (in some form) to attenuate the PWM frequencies, much much higher frequency than the fundamental and baseband harmonics though.

author: max666
author_rank: Frequent Contributor
timestamp: November 10, 2015, 11:46:45 am
content: Oh right, we are talking ~250 Hz here.

author: lm3baker
author_rank: Contributor
timestamp: December 07, 2015, 11:04:28 pm
content: Quote from: VK3DRB on November 07, 2015, 10:45:36 amNope. 253 Volts in Victoria.http://www.esc.vic.gov.au/getattachment/a6b85585-af03-4a2e-bb17-dfff74bbd886/Electricity-Distribution-Code-January-2011.pdf255V is out-of-spec (but sadly not uncommon), and 264V would give a lot of modern equipment a short life.