# 5914



## KenL (Sep 26, 2012)

I am in the middle of rebuilding a 5914 lathe. The main thing that I am doing is doing away with the intermediate drive.  I already have bought a hitachi vfd for it. It came with an old brush single phase motor so I need to switch it out to a 3phase motor. Shouldn't it be a 3450 rpm? Thanks


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## PurpLev (Sep 29, 2012)

I can check on my 4900 motor spec to see what it's running at. can't recall at the moment. 

quick Q though - are you planning to bypass the intermediate drive all together including the quick-disconnect clutch mechanism? or keep that one in the loop?


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## KenL (Sep 30, 2012)

Purplev

Thanks for responding. Yes I have done away with all of the intermediate drive and hardware. According to my calculations a 1700 rpm motor would only give me a top spindle rpm of around 1150. The 3450 should top out at around 2150 rpm. I was just wondering if that is what others had come up with. Basically just trying to confirm that I was on the right track?


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## PurpLev (Sep 30, 2012)

The motor on my 4900 is 1800rpm. Highest spindle rpm is 1700. The 5900 might be different though.what does the vs ring max out at?


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## Pacer (Sep 30, 2012)

I just cant imagine using/needing 2000+ rpm. I'm still a bit of a noobie, but on the 2-3 lathes I've had, I have only ran one in the 1000-1200rpm range a few times to polish a shaft. I have a highly skilled machinist friend and Ive heard him go off on ever needing more than 12-1400rpm - like me, Ive seen him go to 10-1200rpm and polish a shaft

Also, since youve already got the Hitachi (good choice by the way) you can program it to run at a higher freq - say 75 - 90hz - and gain more rpm off the 1700 motor.

What _are_ some uses for high rpm??


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## FarFar (Sep 30, 2012)

Hello Pacer

Please look at the picture.The end face was cut with carbide 1200 rpm and diameter is 100mm .As You can se surface finish about half way to center  goes down.I did not dare go faster but speed is good for carbide .
Three phase motors can easily be VFDed to double speed.I use a six pole ie 950 rpm at 50 hertz and I tested it to 100 Hertz without problems.The question to Kenl is what is the biggest V belt disc on spindle and let us have a picture

Kind regards

Farfar


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## KenL (Sep 30, 2012)

Ok the lathe form the  factory was set up to be able to operate from 52rpm to 2000 rpm.  Spindle speed not using back gears. In pre calculations a 1800 rpm motor running at that speed will not give you 2000 rpm using the pulley arrangement on the lathe. Which is 4 inch on drive motor and 6 inch on spindle shaft. Like I said I did away with variable drive shaft and pulleys. I would post pictures but having trouble with that on my iPad. Anyway after hooking up vfd and using it. Running the drive at 54hz. Which should give me 2000 rpm, I can't imagine ever needing that kind of rpms? Looks like 20 to 35 hz is where it would be ran most of the time.
 So should I leave it alone or put a 1800 rpm motor on it  so it would be ran at 40 to 60 hz? Which is the better hz to run at?


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## joe_m (Oct 1, 2012)

I am NOT an electrician but if it was me I'd go find a 1750-1800 motor and put that on. Otherwise you're talking about long-term use of a motor at half the designed frequency. 3-phase motors can take a beating, but still that doesn't seem right. And you'll have some loss of hp. Having said that, I'm sure someone will jump in and say they ARE an electrician, and that they have wired their entire house to run off a 3-phase generator and a shop-made VFD that drops the hertz down to 20 (except when they want to dim the lights for the wife - then they turn the dial down to 10). This article talks about the effects of running a 60hz rated motor at 50:

http://www.motorsanddrives.com/cowern/motorterms25.html

good luck
Joe


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## PurpLev (Oct 1, 2012)

Generally speaking the motors run best at full speed (60hz for US current) as most of these motors use a fan to cool them down that is designed to run at full speed (1800rpm for a 1800rpm motor = 60hz on VFD). running it at lower Hz results in motor overheating is run for long periods of time and/or under load. depending on how much lower you are planning on running it would affect the long term longevity of the motor. 

I personally run it using the belts for nominal speeds keeping the motor at 60Hz at all times unless I temporarily need an inbetween or a change of speed on the fly. 

As for the motor - as long as you keep the same RPMs that the spindle is designed to support you can use any motor you choose to. Looking at the 5900 brochure it shows that the shipped motors with the lathes run at 1425rpm at 50hz making this a 1700rpm/1800rpm motor.

higher RPMs are good for working on small diameter aluminum, or when using carbide, for mass production, or to turn wood. not necessary, but nice to have if you can. If I were you I'd just figure out the RPMs I'd want to run (keeping it within the spindle max rpm capacity) and choose a motor/VFD combo that would supply that.


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## Pacer (Oct 1, 2012)

I guess we all do it differently, I have 3 VFDs and I run the motors all across the range. I'll power tap or single point thread at 5hz or run a fly cutter at 10-15hz. I probably run them in the 30-40hz range the most, using the gear box or belts set in the mid ranges. Aside from getting the house current changed to 3ph, the VFD gives you all these other wonderful benefits.


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## KenL (Oct 1, 2012)

Pacer do you run it at 10-15hz very much. Do you notice much torque loss?


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## Pacer (Oct 2, 2012)

Yes there is torque loss - and, understandably so... but I have never seen any indication that the VFD is affected by operation this way, and its pretty surprising just what a low hz setting will do - It will just simply stop, and when load is removed it will again operate. And, even on occasion it will throw a default, but here again, I just hit the 'reset' button and away it goes.

It has been mentioned that over heating of the motor can occur when using low hz due to the fan not turning as fast as necessary - and, logically this would seem to be the case, but, I have often had a situation where I was operating at low hz for an extended period and would frequently place my hand on the motor housing to check for heat build up --- have never even had a hint of heat.

As I mentioned, probably 80-90% of my use is in the 30-50hz range.

Did I mention I _LOVE_ my VFD's!!:thumbsup:


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## PurpLev (Oct 2, 2012)

Pacer said:


> I have often had a situation where I was operating at low hz for an extended period and would frequently place my hand on the motor housing to check for heat build up --- have never even had a hint of heat.
> ...
> As I mentioned, probably 80-90% of my use is in the 30-50hz range.



That is good to know. makes me want to setup the lathe on top speed and use the VFD to run it at 30-50hz for a while and check motor heat myself as it would make changing speeds quicker. until now I was just taking the "better safe than sorry" approach babying the motor. As for the 30-50hz range, I think that would be considered fast enough to keep those fans functional as opposed to 5-10hz. 

Thanks for the post.


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## electromecch31 (Apr 5, 2013)

Thanks guys for a very interesting subject I've always wanted to hook up a VFD to my late.
What are some of the other advantages can you go from single phase to 3 phase?

Sent from my SCH-R760 using Tapatalk 2


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## electromecch31 (Apr 5, 2013)

I forgot to ask what is the price for the vfd and also how hard is it to hook it up
?
 I built my rotary phase converter how hard is it compared to that.

Sent from my SCH-R760 using Tapatalk 2


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## PurpLev (Apr 5, 2013)

electromecch31 said:


> Thanks guys for a very interesting subject I've always wanted to hook up a VFD to my late.
> What are some of the other advantages can you go from single phase to 3 phase?
> 
> Sent from my SCH-R760 using Tapatalk 2





electromecch31 said:


> I forgot to ask what is the price for the vfd and also how hard is it to hook it up
> ?
> I built my rotary phase converter how hard is it compared to that.
> 
> Sent from my SCH-R760 using Tapatalk 2



the main benefits are :

you can run a 3 phase motor on a single phase outet
you get variable speed control
remote control of power and VS
it is compact and quiet compared to a rotary phase converter.

that said, a RPC is simpler than a VFD in both design and installation as there is a simple power in->power out whereas with a VFD you have to do some programming and setting of the unit.


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