Phase Converter Capacitors

[@markdoble9698]

As a lift test engineer for thirty five years, I can confirm that many lifts have been installed using phase converters, especially along the south coast, where two phase supplies are more common than you might expect. The cost of upgrading the building to a three phase supply is often prohibitive, which is why the phase converter option is available. Hydraulic lifts are invariably used due to their control and drive systems not having to be adjacent to the lift equipment, as was the case in the video, and their being more tolerant of phase converted supplies. This was a machine room cabinet version, driving what looked like a six person lift car, it was probably at the limit which a phase converter could cope with and, even then, the speed of the lift would have to be much reduced, as a faster lift would require a bigger horse-power motor and pump. Hydraulic lifts actually have another advantage over their traction alternatives, in that all down journeys are virtually power free, with just a controlled gravitational descent. In a block of flats, a lift with down collective control, should be able to achieve running costs comparable, or even lower than a traction lift, which requires power to operate in both directions. However, phase converter lifts frequently fail to perform adequately, often not being able to lift the full rated load but, even when they do flounder under load, they are still preferable for some who may struggle walking up several flights of stairs. The phase converter looked like one supplied by Motorun, these were used extensively by lift companies for this purpose and generally proved to be reliable enough in operation, requiring little in the way of setting up or adjusting, but ultimately, they were just another piece of kit to go wrong when used continuously as lifts invariably are. Traction lifts seldom, if ever, operate on phase converters, the reason being that most modern traction lifts use variable voltage motors for speed and braking control which I have no doubt would be quite hopeless with a phase converter supply. Traction lifts, for those who are interested, are balanced at half load, thus power is only required to lift half the load of the lift when running up, which also equates to half the load of the lift when travelling down empty, although machine room less versions are often balanced at 40% load, as most lifts virtually never actually carry a full load, so the lift would only very occasionally have to work hard at lifting an imbalanced load, therefore allowing for slightly smaller drive equipment to be utilised compared to more traditionally located machine rooms, or where the duty cycle of the lift clearly demands a more balanced arrangement. Hydraulic lifts are more expensive to run in a very busy environment, but there flexibility in the positioning, and the compact nature, of all the associated drive equipment, does make them a viable alternative to traction lifts in many scenarios... their biggest disadvantage however, is that they are much noisier in operation compared to their traction counterparts, particularly when being driven through a phase converter.

[@SproutyPottedPlant]

Now if only they could all have full intelligent levelling and pre doors that would be nice.

[@leehewitt9559]

Mark Doble very interesting indeed. Thank you for the input...

[@simonschertler3034]

I am so happy that in Germany Austria and Switzerland all buildings have a 3phase supply. So I have never seen such a device. Here such capacitors are used for phase shifting / cos phi correction

[@TheChaps83]

Or for small motors (circulating pumps, etc... ) But capacitors converter for a 15kw lift wow !

[@Fabi33677]

they are used like TheChaps83 said in small motors but usually not for motors with more than 3kw because thats pretty much the limit of a single phase. And 2 phase supply in germany is pretty uncommon to say the least.

[@Marcel_Germann]

But in old installations sometimes you don't have three phase in Germany. So you have to use a "Steinmetzschaltung" with a capacitor. de.wikipedia.org/wiki/Steinmetzschaltung In my workshop for long years I had only a single phase supply, but in the house itself it was three-phase. And 2-phase is pretty uncommon, you normally have three-phase (3x230/400), single phase (230V) or split-phase (2x115/230V). The first three-phase system in Germany had a voltage of 3x127/220V. That's the reason the Schuko system was not designed as a polarised connection. Instead of the neutral there was a second line conductor, mostly in split-phase (disassembled in the 1950s) or this three-phase system where the lines had 127V against earth and 220V against each other.

[@jwflame]

These devices are not common in the UK. Most larger commercial and industrial buildings have 3 phase. Almost all individual homes have 1 phase, but all appliances for home use are also 1 phase, 3 phase is not required in normal homes. This building is one of the rare exceptions with 3 phase equipment but not a 3 phase supply.

[@Marcel_Germann]

@@jwflame The utility companies here in Germany demand that appliances which have a demand of more than 4.6 kVA must be connected three-phase. They're afraid of something we call "Schieflast" (crooked load) here, where's the load totally unbalanced between the three phases. In a worst case this could damage or destroy transformers and generators in a power plant. They only tolerate old kitchen cookers which are mostly connected on L3 and fused with 25A (mostly L-type MCB).

[@Godzilla941]

Timely. I just replaced a motor capacitor on the furnace blower motor last week that had failed in the exact same way. It was much slower to start than it used to be and would often sit there and hum for a bit. 7.5µF down to 2... Normally I would have been at work but had to take the day off to wait for something to be delivered that I had to sign for. I was listening for the postal truck in a quiet house so I was able to hear things going wrong, catch and correct it before the motor had a chance to burn up.

[@Richardincancale]

What did it hum while it was waiting? Rings of fire by Johnny Cash???

[@allthegearnoidea6752]

Very interesting to see the phase converter in use and large current draw.

[@SeanBZA]

With those they have an internal disconnect in case they go short circuit or low impedance. Thus you need to have clearance at the top section for the disconnection, as this is done by blowing the top off and breaking the internal tabs. Best when putting in the replacements is to use a push on connector, and have the 2 connections coming off from opposite ends of the capacitor bank, so that the current in each capacitor is spread evenly, if they are both at the same capacitor then that one has the highest current flow in it, leading to it failing first. As well use both push on terminals, so 2 strings for each connection commoned at the input terminals, that way none of the internal capacitor busbars is overloaded, and the current through the push on connections is halved. Hydraulic lift, very rare here in South Africa, pretty much every one is wire rope construction, think the only hydraulic was retrofitted to MRL in the city years ago, more that they did not want to have a sump well below the water table to maintain.

[@zvpunry1971]

2:15 The effect is called dielectric absorption: en.wikipedia.org/wiki/Dielectric_absorption 3:15 Having the right capacity doesn't mean they are perfectly fine. They may still have other defects like increased ESR or increased DC leakage.

[@OnStageLighting]

Yeah, the capacitance test on a DMM is a lot less useful than it appears. Not least because the test voltage is weedy.

[@Garry.Anderson]

Supplied plenty of drives for such applications, it works fine as long as we can get a DC bus large enough to support the installed motor (600vdc on a 415vac). 2 phase installs work out of the box (we just have to oversize a little as only 2 of the 3 input IGBTs are going to have to deliver the full load), single phase much the same but with a step up transformer. Looking at the lift, I'm guessing the phase converter pre-dates the lift installation?

[@jwflame]

Both lift and converter installed at the same time. Whether the converter was actually a new one is another story.

[@Garry.Anderson]

@@jwflame interesting, I suppose the use of VF drives on hydraulic lifts has only become more common in the last 10 years, altho I recall commissioning my 1st in 2004. I'd be amazed if a phase converter was used on a new installation today.

[@markdoble736]

@@Garry.Anderson There is no need to have VF control on hydraulic lifts as all speed and levelling control is either done with solenoid or motorised valves. Some of these systems are quite sophisticated, but basically, all control is done hydraulically, the motor is purely there to provide pressure for up direction movement, all other control is done through the valve block.

[@Garry.Anderson]

@@markdoble736 back in the good old days you would be correct, but now speed control of the lift can be achieved by regulating motor/pump speed thus reducing overall power consumption, not generating any unwanted heat by running a motor at 50hz and dumping back to tank (either for speed regulation or during Accel/Decel), they offer reduced starting peak current on the grid, Check out Bucher (who I used to work for back when VF hydraulics were launched) Hydroware, Blain etc..they all have VF hydraulic solutions. I'd agree that VF hydraulics are not cost effective for all applications, but then with all the MRL tractions going in the hydraulic packages need to have something to win back the consultants favour.

[@markdoble736]

@@Garry.Anderson I wasn't suggesting they don't exist, I simply meant, that for most hydraulic lifts, they aren't necessary. The more "exotic" solutions, including all the gas assisted variants, are just too complicated and not cost effective for use on the vast majority of low to medium rise lifts with 6 to 8 person loads at speeds no greater than 0.5m/s to 0.63m/s with a less than 80% duty cycle. Outside of these parameters, then the need for much better control, efficiency and heat dissipation does indeed require more advanced operating systems.

[@johnsimpson8263]

I installed power to a cell phone tower once that was supposed to be three phase supply. The local lines company took the request and said all good. ....... NO. The lineman who did the survey had miscounted. He saw four wires and assumed three phases and a neutral. But there were two phases, a neutral and a street light line. Cell tower was converted to a single phase supply. Oops.

[@abeleski]

No cap disassembly? 😥

[@MrHack4never]

Just supply it with 1KV, Then it will open itself

[@jwflame]

Nothing really to see in these - they are wound super tight with no gaps and the whole lot is potted in resin, so it's just a solid mass inside.

[@calmeilles]

Sometimes they disassemble themselves. :) flic.kr/p/fKARzn

[@someonesomewhere1240]

Given it's full of capacitors, I imagine that the power factor on that at idle is going to be pretty poor - 600VA maybe, but not 600W.

[@TiptreeJams]

I wonder if the differences in capacitor change is down to the consistency / quality of the original manufacturing process or do some capacitors get stressed more than others in actual use. All very interesting.

[@jwflame]

May be a result of how they were installed - the original connecting wires were at the centre of the bank of capacitors so some may have been more loaded than others. Wires can be seen in the inset picture at 1:10 (larger blue wires onto the 4th capacitor pair) . The new ones were done with the connections at both ends rather than the centre.

[@mikenewman4078]

It would be interesting to know where each capacitor was connected and mounted and in which bank. The connection method shown introduces stray inductance between capacitors and increasing further from the connection point. This leads to uneven load sharing which wears out some of the capacitors. Traction inverter manufacturers i.e. GE and Siemens go to great lengths to reduce stray inductance within their capacitor banks, primarily by utilising wide flat busbars. Granted the application is more onerous due to switching effects, but the principle still applies. Load sharing can be improved by installing commoned tappings along the length of any parallel connected bank that uses circular wires (effectively radial connection). Alternatively banks with individual capacitors soldered / bolted through a printed circuit board include much less inductive reactance and resistance.

[@stuarthossack7906]

How many Amps going up when the lift is at capacity? any idea? Thanks.

[@Stelios.Posantzis]

Very useful! After 10yrs of continuous use, 30% are within spec., 40% within tolerance and 30% fail. Quite useful to know when in the market for second hand parts. I wonder what the theoretical failure rates are and how these numbers tally up with them. The other question is how the first two groups will move in the space of the next 5-10 years. Is there an equivalent application one may use them that is not mission critical, such as a wind farm, perhaps? What was the exact construction (i.e. pp, pp in oil etc.) of these caps and what were their current and voltage ratings?

[@normanboyes4983]

Stelios Posantzis Classic bathtub failure curve.

[@extrastuff9463]

Well there's more to their spec than just the capacitance, I wonder how other values like equivalent series resistance (ESR) and such are affected by age and cycles they went through. During the repairs electrolytic caps will occasionally seem fine with a regular DMM checking its capacitance, but when I bothered to take the LCR meter out their ESR and other values were all out of whack compared to the other similar caps in there (probably as a result of losing some of their electrolyte inside?)

[@Stelios.Posantzis]

Norman Boyes : yes, but how do you scale the horizontal axis?

[@normanboyes4983]

Stelios Posantzis time

[@Stelios.Posantzis]

Extra stuff : I guess only people who own many inverters (such as those with PV's installations etc.) and do regular maintenance on them might have the patience and interest to perform such measurements - let alone having the specialist equipment required. I suppose it would make sense for such a person to try to push the margins of usable life of the capacitors as far as possible in order to bring down maintenance costs.

[@TheChipmunk2008]

unusual here (southampton) to find a building big enough to require a lift with a single (or 2 phase?!) supply. Did the building originally have 3ph and one joint failed?

[@TheChipmunk2008]

(phase balancing is something SSE and their predecessors are usually quite anal about)

[@TheChipmunk2008]

(secondary reply... weird that the developer wouldn't check with the supply authority. Is this an area that used to have a small supplier prior to the SEB? )

[@Garry.Anderson]

Pretty common on the south coast in retirement homes where the building is in a residential area...I've worked on plenty

[@jwflame]

In a way - the building was wired for 3 phase, main incoming fuse cabinet is a 3 phase one, but it's connected and labelled red-red-blue, the yellow phase is not there. Apparently the failure is the cable in the road, and it's been failed for many years. A price was obtained to get the missing phase but the only options were dig up a very long length of road, or bring in another supply from another road on the other side of the site. In both cases the indicative quote was an absolute minimum of £20k.

[@jwflame]

@pmailkeey Probably in theory. in reality, they will do nothing unless it's paid for. Electricity is charged on usage, not whether it's single or 3 phase.

[@officer_baitlyn]

why does this lift draw so much more current when lifting? i thought lifts were fitted with nice and balanced counterweights

[@lordsummerisle87]

Lifts that are drawn by a cable yes are counterbalanced, but this is a hydraulic lift (commonly retrofitted to buildings that weren't intended for lifts because the structural requirements are simpler). Essentially it's a metal box on top of a huge telescoping hydraulic ram, with associated hydraulic pump etc. The pump is powered by a 3-phase motor.

[@jwflame]

Hydraulic lift - no counterweight, cheap to install but expensive to operate. A choice driven entirely by the installation cost, no consideration given to running costs.

[@officer_baitlyn]

Alright, thanks for the responses, I guess that makes sense then, haven't seen many of those around where I live

[@SproutyPottedPlant]

It will probably get modernised to become a MRL in no time!

[@Tangobaldy]

omg a lift video. Thank you. What would the amps be going up in a full lift?

[@burgersnchips]

Wouldn't it be better to use a VFD to output three phase?

[@jwflame]

Probably, but that would require significant modifications to the lift controls which would cost many times more than replacing the capacitors.

[@burgersnchips]

@@jwflame fair enough

[@241mrmark]

And there was me hoping to install one (an RPC) to power a 7.5hp/5.5kw spindle moulder. What do you think - although electrically qualified, given the outlay (and risk), any advice greatly appreciated !!!

[@Basement-Science]

I´ve got a whole bunch of different electrolytic capacitors in a similar formfactor. On all of them there is a low resistance or even a short between negative and the metal can. This does not seem to be intentional. Any idea why they may be in that state? Is that a common failure?

[@BenjaminEsposti]

On old caps they used tar or wax to hold the cap "roll" in place. If the capacitor overheats, the wax/tar can melt. In some cases, if the capacitor is placed with the vent pointing down, the melted wax will plug the pressure relief vent and it will explode! :D

[@therealjammit]

It may simply mean that the can is intentionally shorted to the negative terminal for use as a common ground. Either for convenience or for help in reducing radiated noise. When they "wind" the plates and insulators around each other (jelly roll), the outer foil is pressed against the can. If they add another insulator to separate the outer foil from the can they reduce the space available for added capacity.

[@TheChipmunk2008]

Electrolytics with that form factor may well be intended to have negative to the can. The caps John was showing are for AC use so the bolt (stud) is purely for mounting

[@Basement-Science]

@@therealjammit If it was intentional, I would expect the resistance to the can to be near zero. Some of these caps had almost an ohm to the can, one even had a few hundred ohms.

[@Basement-Science]

@@BenjaminEsposti I was imagining it was something to do with the outer layer of the roll. I´m not sure if these contain wax or not, they are at least over 30 years old, so it´s possible. The capacitance on all of them is still close to spec btw.

[@Mr_Jack_Shelby]

Another fantastic video, thanks JW

[@DIMTips]

Can't wait for graphene capacitors to take over and make everything a lot smaller.

[@vylbird8014]

Don't get too excited. Graphene capacitors would suffer the same drawback as existing ultracaps: Tremendous capacitance, but very low voltage tolerance.

[@DIMTips]

This is a completely different subject but the life time vs lithium ion has to be better thou. There could be many more applications than what we have today.

[@Equiluxe1]

It is normally the dielectric that fails in capacitors very often from mechanical movement, so I cannot see how graphene will really help here other than perhaps allow a thinner conductive element which in itself will lead to failures.

[@DIMTips]

@@Equiluxe1 that is a fair point. There is however some good videos by @graphene-info which demonstrate the effectiveness of graphene super capacitors

[@richardwash6678]

Great video John.👍

[@brunobarros3597]

Good afternoon I enjoyed seeing your video I would like to build a 230v single phase to 380v three phase converter. Where can I find the required assembly diagram and components? Thanks Bruno Barros

[@chrismaher5506]

Lift control spa controller What brand elevator John?

How ,many amps does it draw when the lift is full going up?

Also what is the maximum amperage you can draw on a single phase supply? with 3 phases you have three times the amperage as you have 3 feeds.

[@Marcel_Germann]

@ You can't calculate that easy between single and three-phase demand. First you have different voltages, single phase is here 230V against neutral or earth/ground. In three-phase you have 3x230/400, meaning every line got 230V against neutral or earth/ground but 400V against each other. To calculate the demand in a single phase system you multiply the voltage with the amperage and the cos phi. If the load is purely resistive (heating element) you can neglect the cos phi because it is 1. In a three-phase system it is: Voltage x current x sqrt of 3 = demand For example the calculation of a kitchen cooker: 400V x 16A x 1,73 (precise enough for practical use) = 11 kW voltage of single phase against earth/ground x sqrt of 3 = voltage of the lines against each other. So if you have 240V single phase it would be 415V. The current you can draw is limited by the source of energy and the dimension of the cables. Three-phase only reduces the necessary size of the conductors, but you need more conductors (4 or 5 depending on if the neutral is required or not).

@@@Marcel_Germann When they lay out the cables for a street they are all fed with same size cables, and they try to distribute the 3 phases so the loading across the 3 phases will be the same. In 3 phase building they distribute the 3 phases most buildings only get the single phase, so the cable thickness will be the same.. The building of this lift had two phases supplied as one would be overloaded. The lift was drawing 64 amps with no one in the lift, and with other devices in the building could exceed the 100amp supply. Also would there be a voltage drop if the lift was heavily used and other equipment being used at the same time as this phase inverter is a bodge to get round the lack of 3 phase supply.

[@Marcel_Germann]

@ Big buildings are not connected to the low voltage (in case of the UK 3x240/415V), they mostly are connected to the medium voltage ring and have big transformers in the cellar. So it is actually not comparable.

@@pmailkeey my supply is 100amp, 60 amp will be on the low side and most 60amp would have been upgraded although a lot should still exist. Electric fires, cookers, washing machines,dish washers, tumble dryers soon you will be over 60amps.

[@colintinker7778]

How about peeling the cases off a bad capacitor and a good one. I'd like to see the difference between the innards and what the failure is.

[@jwflame]

Have attempted that before - the insides are totally solid and potted in resin so nothing to see. This is a smaller one, but the same type of construction: facebook.com/jwflame/videos/320897598422229/

[@colintinker7778]

@@jwflame I guess the connections to the foil must have failed due to the stresses of the heavy current flowing.

[@Mark1024MAK]

Colin Tinker - the normal failure mode is the metallisation on either side of the dielectric sacrificing itself whenever a high voltage damages the dielectric. This normally prevents a permanent short circuit, but every time the metallisation layers are damaged, the overall value of capacitance falls. Over a long time period, the value can fail substantially.

[@colintinker7778]

@@Mark1024MAK That makes sense. Thanks for the explanation.

[@grantrennie]

Good morning from Argyll UK, thanks for the great video, am a night owl myself as many techies are..

[@1966myke]

Has the convertor got a dummy load motor spinning as well as the lift motor?

[@jwflame]

No, just a large transformer and the capacitors.

[@SproutyPottedPlant]

Omg Oronas are quite nice lifts for a generic, perhaps not the hydraulic ones though.

[@stevewilliams587]

Hi JW I am in the UK and looking to build a phase converter. I can not source big capacitors. Can you help me ? Google either links me to suppliers of small items or distributors in the USA.

[@jwflame]

uk.farnell.com/c/passive-components/capacitors/film-capacitors/motor-run-motor-start-capacitors uk.farnell.com/c/passive-components/capacitors/film-capacitors/power-factor-correction-pfc-capacitors www.rapidonline.com/motor-run-capacitors uk.rs-online.com/web/c/passive-components/capacitors/polypropylene-film-capacitors/?applied-dimensions=4294455447,4294698844

[@matthewday7565]

Is there a huge inductor to make the other phase? Come to think of it, you could only shift 90 degrees that way, so I guess maybe the phases are inductive, capacitive and inverting autotransformer?

[@jwflame]

instagram.com/p/BtWhwLuhsHb/ - large transformer in the front left.

[@koffibanan3099]

Jesus, i didn't know a lift was so power hungry? 600W idle??

[@jwflame]

Converter is 1 amp just on it's own with nothing connected. The rest is the lift lighting, control panel and various other items such as the landing indicators, emergency intercom and so on. Lifts in general are expensive things to install and operate.

[@jazbell7]

Those are still better than the older rotary converters which were basically motor-generator sets.

[@jazbell7]

@pmailkeey An AC to AC MG set would not be a normal thing, it would take a single phase synchronous motor, a three phase synchronous alternator and an exciter generator plus controls plus anti-vibration mounts etc. Sounds expensive.

[@JGnLAU8OAWF6]

Simple VFD is far better

[@stevecraft00]

A hydraulic lift? I'm guessing a traditional lift with a counterweight might actually draw less current going up than down when empty since the cw is heavier than the lift car empty.

[@jwflame]

Yes, a proper lift would use far less power. This hydraulic effort was put in because it was cheap, and those paying for it were not the ones having to pay for the operating costs.

[@stevecraft00]

There's a shopping centre near me where I think all the lifts are hydraulic. Certainly there are some where the hydraulic cylinder is visible through glass screens and clearly no cables. They have a certain bounce to them when riding them.

[@markdoble736]

@@jwflame There is nothing improper about hydraulic lifts, they just simply use a different means to operate. Traction lifts, until fairly recently, had the distinct disadvantage of needing a proper machine room to house all the drive equipment, whereas hydraulic lifts could have the drive system situated virtually anywhere, often many metres away from the lift shaft. Hydraulic lifts also have reduced shaft headroom which allowed building designers to dispense with roof mounted machine rooms, a feature that was much sort after a few years ago. Hydraulic equipment isn't necessarily cheaper either. For long travel lifts the associated shaft mounted ram, ropes, diverters and safety gear could be more expensive than some cheaper traction lifts, but still have all the benefits of remote machine rooms. Small housing apartments and existing multi occupancy housing conversions often have no choice but to use hydraulic lifts for vertical transport due to the limitations of the building design.

[@paulbacon2106]

I divided the 15kW by 64amp to get 234volt dose this mean the voltage of a single phase is 234v and if we are looking at one phase do we times all the readings by three to get overall power and current ???

[@lozzamanuk]

No. Because this is single phase supply.

[@paulbacon2106]

lozzamanuk hi thank for the reply would it had bin the cas if it was a 3 phase supply

[@lozzamanuk]

@@paulbacon2106 Yes, of course if the supply is 3 phase you need to multiply by 3 if only measuring a single phase. For a single piece of equipment the load should be equal across each phase.

[@Marcel_Germann]

@@lozzamanuk This calculation (multiply with 3) is only correct if the loads on all three phases are absolutely equal (balanced or symetric load). But in some cases you won't have that.

[@lozzamanuk]

@pmailkeey Phase to Phase yes, but phase to neutral will be more like 240v RMS. I usually am around 242V at home.

[@madbstard1]

If you haven't scrapped them, send the caps to Julian Ilett - he loves his caps :D

[@TheChipmunk2008]

Yeah but only super ones :)

[@uK8cvPAq]

That man is a hoarder!

[@antoineroquentin2297]

ESR would be interesting for those which have capacity left

[@Eeroke]

Two phases would be enough to hex up the missing third with clever transformer arrangements, though.

[@apollorobb]

I would have thought they would have used a rotary instead of a static convertor .Much more efficient and reliable

[@TheChipmunk2008]

But that needs maintenance and will last longer. You think a developer would think more than 'end of contract' ahead?

[@jwflame]

Yes - if those constructing the place actually cared. The original contractors went bust before it was completed, some other lot were called in to complete the build, then they went bust as well. Pretty much everything in this building has been done on the cheap, and that's not just the electrical side.

[@shaz9425]

hi i have a kids electric quad the charger has a green and blue wire on the quad it has a blacke and red not sure witch ones go wer

[@jwflame]

10 seconds with a multimeter would confirm which is what. Otherwise it's just guessing.

[@jed-henrywitkowski6470]

It reminds me of a flash-bang grenade. Oh, and have you ever chucked small capacitors in the grill? Fire+capacitor is kind of neat.

[@mikecarrington7096]

Very interesting indeed.

[@SproutyPottedPlant]

Could you do more videos on lifts? They are such awesome machines!

[@hyperion8008]

I imagine once that lift is filled with one or two typical fat Brits that current draw will be a lot more!

[@normanboyes4983]

It should be sort of self regulating if the lift held 6 skinny Brits but could only physically fit 3 fat Brits in then the overall weight carried would be broadly similar.

[@teravolt1195]

Not so much a problem anymore, VFDs are now cost effective enough to drive these 3 phase motors in a single phase environment.

[@lordsummerisle87]

Unless there's multiple motors in the lift, or switchgear between the phase converter and motor. Conversion to a VFD would require that all motor controls be rewired as inputs to the VFD with the motor driven directly off the VFD. With the amount of call-prioritising logic and safety interlocks on a lift that doesn't seem very cost effective to me, whereas refurbishing a static phase converter like this would require minimal downtime.

[@Garry.Anderson]

The only additional motor on this installation would be for the lift doors which will be 230vac max, so no problem there. Everything else will be fed from an isolation transformer likely fed from phase and neutral and typically transformed down to 110v or 24v so again no hassles...the biggest drama would be changing the sequencing of the lift to allow operation for VFD operation as the timing would be a little different than a couple of motor contractors banging in when the lift needs to travel up, it's perfectly possible however.

[@teravolt1195]

Agreed, won't work for every scenario and may not work in John's application. Workshops with drill presses and lathes however benefit. It would be possible to VF drive that lift, but changing the control transformer from 415V to 240V and the possibility of other motors as said doesn't make it viable there.

[@johnclarke2997]

Often just as easy to convert the system to a full on 3 phase with a rotary converter.

[@embeddedusystems]

Would love to see Keysight (or someone!) send you an LCR meter!

[@rahidiqbal4682]

Good

[@maicod]

interesting to watch

[@hausaffe100]

shouldn't they use inverters these days?

[@stuartmcconnachie]

4:04 No, 8 = √64 😝

[@750kv8]

"3-phase not available".... Well, that's the power company lying into the customer's face for an extra fee. In MOST parts of the world 3-phase comes right near homes offices plants factories, even in like NA where most distribution transformers are single phase. Extra fee for what it takes is often just 1 more cable of a few or a few 10 meters, 2 more single phase-, or a 3-phase meter, 2 more circuit breakers, per household. The usual reasoning, that "household appliances don't need 3-phase", is also a lie. A lot of people have some sort of a backyard workshop, where 3-phase could make life just a bit easier. Also, 3-phase motors on a single phase supply really just need a single runcap, and in many cases, NO converter whatsoever (no start relay or button & startcap either), since the motor becomes its own converter internally. I have a 750 W (1 HP) motor, starts and runs just fine on a 10 µF runcap.

[@jwflame]

In this installation, the 'extra fee' was in excess of £20k, as it would have involved several 100 metres of new cabling being installed in the road, as the existing cable only has 2 usable phases in it. Although the building is new (about 15 years), the road previously had buildings from the 1930s - 1950s, and cabling of a similar age.

[@andreim841]

So basically it's a VFD's grandfather...

[@Marcel_Germann]

It is called "Steinmetz circuit".

[@spodule6000]

HOUSE !!!

[@coldfinger459sub0]

Where those electrolytic capacitors ? or poly propylene ?.

[@jwflame]

Polypropylene film, 450V AC.

[@mikefromspace]

Is there such a thing as a cap with 3 layers of metal vs 2? (for 3 phase)

[@jwflame]

No. There were multi section capacitors which were used in old radios and tvs, but they were just 2 or more capacitors in the same can.