240 volt vacuum motors - fan search.

[riga team]

[ivanhoew]

yes i saw that anatolij ,looks like the perfect bit of kit !tony check out some books by a chap called jim cox,one called 'electric motors in the home workshop',and another called 'electric motors'.the thing i was saying about a capacitor is form these books ,might be total pants ,but it wont cost much to try (barring of course the trip in the ambulance)and it seems according to the text that ''these motors will happily operate from domestic single phase 240v ac supplies''as long as its a 6 terminal type of 3 ph motor . if one wires it in a delta mode ,then give it some juice ,itll need spinning up manually then run on one winding at reduced power ,but if one uses a cap and puts it across the live to t2 connection ,it can with a low starting torque set it running then makes the motor see that winding as out of ph ,so running almost as well as a normal 3 ph feed.please dont ask me the det cos im deffinately not a electronics expert !! but i do have a honking grt 5hp 3ph motor ,and some big capacitors and a fuse box ....if i wasnt busing intercoolng my mini ,and building a adjustable split scroll on the turbo v8 tvr in the garage ,it'd be done by now ,and i'd either be cavorting around happily or alternatively going round to the neighbours house to say sorry bout the power cut ,and have you got any ice !!
regards robert.

[Tony]

[Tony]

[riga team]

[bruce]

I use a homebuilt 5hp rotary 3 phase converter (RPC) in my shop for my 3 phase equipment. I am running my renegerative blower off it and seems to be working fine. The largest motor I have currently is my 3hp one on my lathe. I have not used it on more than one motor at a time.

I have less than $100 into it. I do not have a starting capacitor on it. I just plug it into a 220 1 phase outlet and it starts right up. Someday I'll get it all wired in correctly and add in the starting cap but it works fine the way it is.

[ivanhoew]

any chance of a wiring diagramn bruce ??

[Tony]

Anatolij,

I use a clever free software utility for converting engineering units, here it is :



20Kpa = 80.295 inches of water

My two eighteen inch blower rotors both reach about roughly 17 inches pressure at 2850 Rpm.
80/17 inches is a pressure increase of 4.705 times
As pressure is tip speed squared, required tip speed increase (sq root 4.705) = 2.169
A diameter increase of 2.169 x 18" = 39"
So I assumed a 36 inch rotor running at 2850 Rpm was being used, that is a standard size, fairly close to the estimated 39 inches.

With these blowers a two pole motor is always used, as the UK is 50Hz, that will be 2850 Rpm.

The minimum flow figure quoted is 0.05 cubic metres/sec = 105.944 CFM
The maximum flow figure quoted is 18 cubic metres/sec = 38,139.84 CFM

I am assuming the smaller blower RL0 is a single entry type, like the white one shown in the picture, and the RL1 are all much larger, and probably dual entry types, like the blue monster shown on the home page.

This all ties in with what I have seen for these types of high pressure blowers, but I could be wrong.

It is interesting that they make blowers with forward facing vanes, reverse facing vanes, and straight vanes. All the high pressure blowers they supply, have the straight vanes, which is normal practice.

[bruce]

Here is a link to a machining forum I visit daily, the link takes you to the Phase converter, VFD forum that is in the main machining forum. You will find all the help you need and plans in there.

[Tony]

[bruce]

Here is a PDF file of one, much more elaborate than the one I am using for my shop.

[ivanhoew]

ok latest is ,the 5hp motor turns out to be a 415volt windings one!! bummer.so what the #### ,iv wired it up anyway ,on a big 200uf capacitor as shown in this book i mentioned .so tomorrow ill turn it on and watch all the lights in my street go out !! lol,should be in theory low torque start ,and about half its rated hp due to the current being half cos the winidngs resistance is double what it would be for a 240 volt motor .if it doesnt work then im off to the scrap yard for another motor .
regards robert .oh .tony did you get yours plugged in ?/ aparently it has to be a capacitor about 40 uf per hp and not a electrolytic one.the ones out of flourescent tube cases are supposed to work .and you stick it across the live and the middle pole next to it in the row of three ,making sure its all wired in delta config .

[Tony]

I did try this, and like yourself only had a 415 volt motor. The results were not good, there was simply not enough starting torque to get it up to correct running speed, even with no load connected.

In the US, what they call single phase is actually the voltage between two phases, so they can use this rotary converter trick to generate a third "phantom" phase.

In the UK and Australia our single phase is the voltage between one phase and neutral, a totally different situation. Building a rotary converter is not going to work for us, unless we already have two phases connected to the house. That would be I suppose, 415 volts "single phase" in the American terminology.

I still think your best option is to get a proper three phase utility connection. It may be a lot easier than you anticipate.

[riga team]

IVANHOEW : If you do not have 380/430 volt of 3 phases: the best will be 230 volt the collector motor of frankness On management thyristor . The invention to feed 380 on 220 1 phases these are two blocks of condensers 1 for start-up 2 worker and loss of capacity : You are ready to lose much ...

[ivanhoew]

well the 415 v motor was to say the least limp and pathetic ,as was expected ,couldnt pull the skin off a rice pudding !!
so off to the magic yard ,and found a nice 3kw 4.1 hp 240v 3ph motor 2880 rpm !! bonza ..result .so ill try that tomorrow and see if its better ..cant be worse thats for sure .
regards robert. oh tony ,in the situation im in at the mo on an ex government resaerch estab ,the q of supply is murky to say the least .