3 phase converter - again

Have you considered a VFD ? I've no direct experience with them , but they get good reviews from those I know who have used them .

I have several VFDs. The biggest advantage to a properly sized VFD is the ability to vary speed (within the capabilities of the motor (mostly cooling)) by varying frequency, and act as phase converter.

The biggest advantage to a rotary phase converter (often called RPC) is the ability to run multiple motors on different pieces of equipment and switch them at the equipment without damaging the RPC.

I don't know of any big advantage to a static phase converter. Price maybe.

There are lots of RPC manufacturers who have guidelines for choosing an RPC size. This is just one of many:

Basically it looks like you would have no issue with a 50HP motor on a

100HP RPC. If its no-load balanced you can run any size motor from fractional horse power to max horse power. I bet you could run a 60HP, and maybe a little more if it has soft start capability. Of course lockup could still cause problems.

Also, if your RPC is well balanced and filtered to provide clean 3 phase power you can run a VFD (or multiple VFDs) down stream of the RPC on individual pieces of equipment.

I DO NOT run an RPC in my shop, but use multiple VFDs on individual machines to act as both a phase converter and speed control. If choosing a VFD for a piece of equipment its considered by many to have a high likelihood of damaging your VFD if you switch the power between the VFD and the motor it is controlling. Use the inputs on the VFD and disconnects should be between the power source and the VFD. I have had a power failure (a few) with VFDs running spindles on machines. I have also powered down a machine a couple times with the disconnect while running. I have not experienced a failure from sudden disconnect of source power other than of course... it had no power. I do not have any switching between the VFD and the motor.

Generally the rule of thumb is if a VFD is used with a single phase source to provide 3 phase output that it should be derated by 30-40%. HOWEVER, there are VFDs sold and marketed specifically for phase conversion that are rated at 100% when used as a phase converter. IN my opinion its not about efficient use of available power, but rather the power handling capability of the capacitors. I could be wrong of course. I often am.

Got a 100A 240V spur. In UK - so 50Hz, for what it's worth. I see rotary converters. Seen one in-real-life. Get converter first then could get equipment with 3-phase motors... So in your experience what's the real deal? What power motor could I run given 100A spur? Is that answer nuanced if not a direct-online (DOL) starter but some sort of autotransformer starter or resistor? I was in a shop which had a WW2 era press where you pushed the handle to a starting position then flipped it across to the run position when you could hear the motor at speed. Sorry if frequently asked. I'd happily follow-up leads.

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100A, 240V is 24 Kilowatts or 32 HP, though as the PFC article below mentions you probably can't use that much.

For the low budget, technically educated hobbyist:

was highly respected in R.C.M and heavily involved in the power systems on the International Space Station.

There are other ways to cobble a spare 3ph motor into a 3 phase rotary converter, including starting it with a pull rope.

Single phase motors may have internal centrifugal Start-Run switches that click back to Start as they slow down after switching them off. If the Start circuit fails they just hum loudly without turning. My father had a bench grinder like that, switch it on while yanking the belt to get it turning, and try to avoid catching a finger in the pulley. The belt was so loose that damage to the finger wasn't serious. I appreciate solid modern technology but I can deal with primitive, at my first factory job the machinery ran on leather belts from overhead line shafts.

In my opinion unless you are familiar with and equipped to troubleshoot AC power, buy a solution from a company whose technical skills you trust. You might ask about Power Factor Correction and see if the salesman refers you to a tech who can explain it, or tries to blow you off.

BTW my house was built for electric heat and wired for 240V, 200A, plenty for any machine tools and welders I could stuff into it. I've been exploring energy conservation and reduced my electricity demand from 4 to 2 KWH per day.

OOPS!!!

I saw 100A and thought 100HP. My bad. Biggest motor on circuit might be 16-20HP. Not 50-60. LOL. Again. My bad.

No worries. I knew that could not be the case.

10HP would be a bonanza.

Thanks everyone for phase converter (1ph->3ph) advice. At least I've touched the subject and have something to think on. I followed the links. Seems like could be done. Converter, then have access to ex industrial machines. Noting Jim's advice "... In my opinion unless you are familiar with and equipped to troubleshoot AC power, buy a solution from a company whose technical skills you trust. ..." unless you wanted the converter to become the project, if you have missions you are on, get one delivered ready-to-run. Regards, Rich S

unless you wanted the converter to become the project, if you have missions you are on, get one delivered ready-to-run. Regards, Rich S

---------- When designing custom industrial test equipment I had to repeatedly decide whether to buy or build parts of it. Usually I was running at or beyond my experience level and would have to study how to build the module and risk delays, though the knowledge would be valuable. My usual compromise was to learn enough that I could buy wisely.

Every time I was pushed into a different branch of electricity/electronics I found I had to learn a new set of test equipment and a new way to think about the flow of electricity. Digital radio was so complicated I had to take night school classes in the mathematics of it.

For audio, TV and telephone communications you look at the voltage on a meter or an oscilloscope. Current might be nice to know but it's difficult and disruptive to measure in-circuit. The useful tool for digital communications over phone lines is the eye pattern. Analyzing it was more artistic judgment than measurement.

If you are interested in the British Enigma project you might like the reference to SIGSALY. Computers arose from the joint US/UK efforts at breaking enemy codes and securing our own. Though an impressive advance your Colossus wasn't quite a true computer, nor were ours of the wartime period. Early developers tried to avoid creating a general-purpose computer because they realized they would lose control of it. "Although ENIAC was designed and primarily used to calculate artillery firing tables ... its first program was a study of the feasibility of the thermonuclear weapon.

For industrial AC motors the basic tool is the clamp-on ammeter, an analog Amprobe when I started, now a digital Fluke if the company is paying for it. Unlike DC circuits the voltage is usually constant and the load's inductive reactance determines the current.

For radio the measured quantity is power and the instrument selectively measures the power flowing in one direction since some of it can echo back from the intended destination. A common example is the SWR meter. I had to learn to operate these for more sophisticated measurements: bought a NanoVNA that I haven't had time to use.

I *should* learn electrics and electronics as a project - but it must be a free-standing project. I have worked so hard on welding - maybe I should continue to do that and graciously accept help when needed and given...

My downfall is wanting to know too much about everything ... and having infinite knowledge at my fingertips has made me more aware of it . I try now to get just the info I need right now to do whatever it is that I'm doing . If I need to know more I can always go back for a second helping . Or even thirds ...

What's a spur?

Hul

Richard Smith snipped-for-privacy@void.com wrote:

I *should* learn electrics and electronics as a project - but it must be a free-standing project. I have worked so hard on welding - maybe I should continue to do that and graciously accept help when needed and given...

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After day and night college courses, Army training and a career in it I'm nowhere near being able to consider myself an electrical engineer, though I'm pretty good in some of the scattered areas where I've worked. As with mechanical engineering the calculus becomes intense in some areas, more than I had to survive in Chemistry. The Army training, which to be fair was on very arcane equipment, began with around 100 in the class, of which 4 of us graduated. I learned the art and craft of building electronic hardware mostly on the job and from examining high end industrial and military equipment.

A good start would be learning Volts, Amps and Watts, resistors, capacitors and inductors (since you use welders), transformers, relays and motors. Digital electronics is an extensively complex assembly of simple building blocks and you don't have to dive too deep into its innards to be able to tame and train a microcomputer, an Arduino for example. Analog electronics, transistors etc, is being swallowed up by Digital.

What's a spur?

Hul

Richard Smith snipped-for-privacy@void.com wrote:

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I took the railway/railroad meaning of 'spur'.

You're lucky he's British instead of Australian.

"Once a jolly swagman camped by a billabong Under the shade of a Coolibah tree And he sang as he watched and waited till his billy boiled "You'll come a Waltzing Matilda with me" Down came a jumbuck to drink at that billabong Up jumped the swagging and grabbed him with glee And he sang as he stowed that jumbuck in his tucker bag "You'll come a Waltzing Matilda with me" Down came the squatter mounted on his thorough-bred Up came the troopers one, two, three "Whose that jolly jumbuck you've got in your tucker bag? You'll come a Waltzing Matilda with me" Up cut the swagging and jumped into the billabong "You'll never catch me alive" said he And his ghost may be heard if you pass by that billabong "Who'll come a Waltzing Matilda with me?"

That's pretty complicated ... I figgered he meant a sub panel . I got one out in my shop , 100 amp feed from the main . Someday I'll fall across a 3 phase motor suitable for my lathe , at which time I'll probably get a VFD to power it . Unless I fall across one that will fit the milling machine first .

In general (?) (well, in UK), lights are on rings and sockets are on rings. Multiple places to draw current off one supply from the breaker.

A spur is when a cable goes direct out of the distribution-board to a single destination.

The cooker has one always (?) because of its high power draw.

Outbuildings often have a spur, as in this case.

In general (?) (well, in UK), lights are on rings and sockets are on rings. Multiple places to draw current off one supply from the breaker.

A spur is when a cable goes direct out of the distribution-board to a single destination.

The cooker has one always (?) because of its high power draw.

Outbuildings often have a spur, as in this case.

I learn during application. The thing that seems to be missed:

• the candidate who has done exactly this before is fictitious

• the right individual has the right area of aptitude learns a lot quickly (typically a lot by networking and getting mentoring) Showing what's wrong with the disagreeing view... I have a lot of knowledge in welding, Non-Destructive Examination and design of steel / metal structures. I, like you earlier described (or was it Bob?), need to know enough to specify what's needed - be "a knowledgeable customer". Delegate the implementation, but oversee the objective is the target and is being achieved. I have to have a fair amount of knowledge on maybe something like 40 topics. Maybe it goes into 100's. A "properly qualified person" (sic.) has "tickets" in one subject. As much use as a chocolate fireguard for driving an endeavour to a goal.

The endeavour and the goal produces the need to acquire a new skill and area of knoweldge, and the context makes that learning part happen and make sense. The "case study" make taking up information hundreds of times faster minimum that abstract study of the general area.

The "case study" might sound narrow if you don't know how learning works, where the person spending time in general study might be the same mistake be expected to have the broad base. But this is not the case. The "general studying approach" will be things which come and go, not consolidated by not having application. Whereas the "case study" appoach, has application, and reward for new learning is seeing application; which feeds into enthused new learning.

Another hard reality the administrator's model doesn't address is the extent of your knowledge is dominatantly dictated by the furtherest you've been in a topic - even if that is a narrow specific-case driven activity - bacause you can "fill-in" "sideways" trivially in all of the domain you did not touch in your lunge to the highest, furthest goal.

I am saddened that here in the UK I have been ready and poised like on the starting line of track running race for most of my would-be career, spending most of the time supporting myself with the likes of welding and often simply doing what I am told to do having to passively watch the "slow motion train wrecks" as the now almost totally dominant managerial layer messes up what (everything?!) they touch...

Example of "learn" for a person with aptitude and has benefitted from

***>good<*** education - that which develops the ability to learn. (my website) 'd done the welding, tested to destruction; which proved to be gross plastic deformation - but that weep of oil down the cylinder and continuing down the sample is the hydraulic cylinder's seal blowing on "that last absolutely final push of the pump handle". [it later proved - I was not at max. pressure, and the seal had simply worn out and / or perished in long heavy use] I was not "grassed-up" but got icy stares and negative annoyed mutterings.

So - I learned about hydraulic cylinders and that was my path into hydraulics.

I made a tool to dissemble the cylinder and after work nipped around with the bits to to the hydraulics supplier at a nearby large industrial estate. Where they looked, pronounced all looked normal and looked to be just the seal - which they found was a standard size. So ordered one, bought circlip pliers knowing these would be needed and paid for all. Then collected seal next day hidden by their door (was after their closing time). Next day fitted new seal, reassembled cylinder - and it was perfect. "Persona grata" again. Asked on here and got a recommendation for a book on hydraulics, bought it and read through it that Christmas. Got my own hydraulic pump and cylinder for tests. Worked at a major engineering Co. with a big hydraulics dept. and got to talk with them and look at major hydraulic motors, etc.

The learning path. in context. It is the way for the fast folk on a mission.

Example of "learn" for a person with aptitude and has benefitted from

***>good<*** education - that which develops the ability to learn. (my website) 'd

• fabricated and welded to design

• tested to destruction, which proved to be gross plastic deformation

• found Finite Element Analysis modelling prediction and physical observation matched exactly

But that weep of oil down the cylinder and continuing down the sample is the hydraulic cylinder's seal blowing on "that last absolutely final push of the pump handle". [it later proved - I was not at max. pressure, and the seal had simply worn out and / or perished in long heavy use] I was not "grassed-up" but got icy stares and annoyed mutterings. Needed to do something, and fast.

So - I learned about hydraulic cylinders and that was my path into hydraulics.

I made a tool to dissemble the cylinder and after work nipped around with the bits to a local hydraulics supplier I'd found in the Web.

They looked, pronounced all looked normal and reckoned was just the seal. Which they found was a less-regular but standard size. So ordered one and bought circlip pliers knowing these would be needed.

Collected seal next day hidden by their door post their closing time. Day after, fitted new seal, reassembled the cylinder - and it was perfect.

"Persona very grata" - not only cylinder good, but ability to repair cylinders as-and-when.

Asked on here and got a recommendation for a book on hydraulics, bought it and read through it that Christmas. Got my own hydraulic pump and cylinder for tests. Worked at a major engineering Co. with a big hydraulics dept. and got to talk with them and look at major hydraulic motors, etc.

The learning path. In context. It is the way for the fast folk on a mission.

There is a Wiki page here with a diagram for a ring and the spur is also discussed: