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I have a variable frequency drive motor from a treadmill. Can I change my drill press to use it? The drill press is a 5 speed bench
mount unit. Is it useful? Any ideas on how to do it? I thought I read an article about it but can't find it. Any help is greatly appreciated.
do you have the controller for the motor?
Yes I do. I have the rheostat, wires ,etc. If I can remove the belt drive (it is a round disc that is threaded on ) I am aware that I will have to machine an adapter to mount the coned pulley or use a single pulley of what size?
Then this should work fine. If this is a brushed motor like most treadmills, be aware of brush life. Long for hobby use, not so much if it's constantly in use.
I've read statements by many people that their treadmill motor conversions weren't successful because most of them are grossly overrated by the manufacturers.
Of course, i should have mentioned the motor will be rated in Chinese hp. They take the Watts drawn by the motor and divide by 746 to get INPUT hp. USA motors are rated on OUTPUT hp.
Also, the Chinese rating is for burst power only, it will not sustain it.
For many uses this is ok.
Thanks, I didn't even know this was a (Chinese or other) practice -Quote:
Originally Posted by jdurand
AFAIK the wattage rating should be for continous duty (unless some other % DF is specified),
and HP/ kW output for on axle/ effective work. In the US and elsewhere.
Hence the efficiency of a motor will be "Input" divided by "Output" - averaging 90-95 %, right?
Chinese motors, especially brushed ones are rated for "peak power". This is the same for other things like power inverters, I have one that proudly states 3000 Watts on the lid but in the instructions you find that's peak. Continuous is 800 Watts.
I recently converted my 10 inch lathe to use a treadmill motor(brushed) rated at “2.75hp”. I used a pulley that allowed the motor to operate in the higher voltage/rpm range. I have threaded at 60 rpm with no problem and turned a 3.5 dia. Losing only 8-10 rpms. I used the motor control from the tread mill and wasn’t smart enough to separate it from the rest of the circuitry and added a tach.
They work great for smaller drill presses. If you have stepped pulleys on the DP now, you could still retain them with the new motor so you have a "speed range" for each of the steps. This was an old beater w/ no motor I got for free and cleaned up and installed a DC motor and speed controller from a treadmill.Quote:
Originally Posted by mdhatter3
Attachment 30318
Most if not all treadmill motors are DC commutated motors, speed variation is by varying the supply voltage.Quote:
Originally Posted by mdhatter3
Variable Frequency drive is a term used for 3 phase AC induction motors, speed variation is done by varying the supply frequency, the voltage is also changed in proportion to the frequency to avoid excessive motor current at low frequency.
Treadmill motors can easily drive a medium size drill press. I used one on a Bridgeport mill once as a temporary measure, it worked OK. http://www.homemadetools.net/forum/h...6661#post84115 Scroll down a little way to see the motor fitting and use.
I use smaller brushed permanent magnet dc treadmill motors on my bench top lathes and mill. Their speeds are different than the original motors, they’re rated ambitiously, and a couple were challenging to mount. I didn’t reuse the flywheel pulleys so I cool them using external fans - here’s my fanciest fan shroud.
Attachment 30319
This picture should give a sense of how their horsepower ratings compare - the motor on top is a regular but older 1-1/2hp 1750 rpm dc motor, and the bottom one is a 2.65hp 6700 rpm treadmill motor.
Attachment 30320
Well - that PM DC motor sucks up max 18 Amps @ 130V, which gives 2,34 kW input & 2,65 hp max, intermittently
but it has only a CONTINOUS output of a mere 1,5 hp @ 95 VDC.
(Which sorta gives me 13,1 A and 1,3 kW IN, for 1,5 hp [or 1,1 kW] OUT at app 5000 rpm. And 200W of heat)
Reason it can be smaller for the same output is:
1) Power=Torque x Angular velocity (RPM), so the PM DC has near 4 times the revs,
but ONLY 1/4 of the torque of the AC motor.
2) Being a PM motor, it doesn't need the AC's bulky field windings, and (being hi-rev)
3) Delivering less torque, it can have a smaller rotor diameter.
Dia equals leverage: You can't loosen wheel bolts with a 6" wrench, you need bigger to get the necessary torque.
Hand down, PWM (Pulse Width Modulation) is the best method for controlling DC motor speed as there is a relationsship between the motors torque and the voltage it receives. PWM speed control is achived by switching the motor on and off very quickly and shortening, or lengthening the gaps between the pulses.
Each "on" pulse is always at full voltage, so regardless of how slow the motor is actually turning, there will be no torque loss.
PWM speed control units are cheap as chips, power supplies not so much but I did find and purchase a unit that will power my 2.5HP 180v motor and has built in PWM speed control, as well as direction control for about £30 on eBay.
Not so.Quote:
Originally Posted by Canobi
In general terms unloaded speed is proportional to applied voltage, so applying your logic "there would be no speed loss", which we know is not the case.
The reality is that unloaded speed is proportional to AVERAGE voltage not the peak voltage of each pulse.
Torque is proportional to current, the characteristics of the motor will smooth out the pulsed nature of the input to give a steadier current than the pulsed voltage. The average current will vary as the average voltage, and so torque will not remain constant as speed is varied.
Over a limited range, torque can be boosted at a given speed by using some velocity feedback which boosts voltage and hence current when mechanical load tries to reduce speed.
Fair comment, I was being a bit too "on paper" there but I'm under the impression that DC and PWM produce higher torque than an AC motor using frequency control.
Well, of course that depends on the relative sizes of the motors but as I pointed out before the torque of the DC motor will reduce with reduced voltage and speed. On the otherhand an AC motor with VFD will maintain torque as the speed reduces. The speed is controlled by the frequency, as that is reduced the current will increase leading to more heating. To avoid that, the VFD will reduce the voltage as well as the frequency to maintain the same current and torque. In fact some VFDs will allow a higher current at low speeds to boost torque but this boost will usually be less than 10%.Quote:
Originally Posted by Canobi
So Tony does that mean I can use a VFD to convert my 3-phase phase lathe to run on single phase service without significant torque loss when reducing rpm?
If you have or acquire a VFD for single phase input, these are the most common type below 4 or 5 kW. You can get VFDs withQuote:
Originally Posted by Saltfever
1 ph only input
3 ph only input
1 and 3 ph input selected by connections and programming the VFD.
All with 3 ph output.
So if you have a 3 ph motor you can easily run it on 1 ph with speed control with a 1 ph input VFD.
The MOTOR torque will remain reasonably constant throughout the speed range and you can probably boost low speed torque by 10% or so by programming the VFD
HOWEVER, that is MOTOR torque not SPINDLE torque. If you have a form of mechanical gearing to change spindle speed (gearbox or pulleys and belts) then you will multiply slow speed torque by the speed reduction ratio. That is, if you halve the spindle speed by mechanical means you will double the spindle torque. On the other hand if you reduce the speed of the MOTOR by a half and maintain the motor torque then the SPINDLE torque will stay the same, it will not double as it would with mechanical speed change. You cannot cheat physics. Many people only focus on the motor torque and are sometimes very disappointed with either DC or 3 ph motors with electronic speed control as a result.
Is there anything that you can do to keep good low spindle speed torque with the benefits of motor speed control? The answer is to use a grossly oversize motor as I did on my mill conversion and recently on my lathe. The mill motor went from 1.5 hp 3 ph to 5 hp 3 ph with VFD and the lathe from 2 hp 1 ph to 5.5 hp 3 ph with VFD. I will never need 5 hp on the mill nor 5.5 hp on the lathe but they give higher low speed torque than smaller motors.
Both the mill and lathe have reduced SPINDLE torque at speeds that would normally require back gears to obtain, and that could present a problem for certain types of work. I do not anticipate this being a problem for me because I am usually after higher speed rather than lower. I occasionally used to use back gears on the lathe for coil winding but that needs minimal torque and a test with the new lathe motor running very slowly was in fact better for coil winding because of the increased smoothness.
Attachment 30340 Attachment 30341 Click for full size.
Here are links to my mill and lathe conversions.
http://www.homemadetools.net/forum/i...515#post135903
http://www.homemadetools.net/forum/h...6661#post84115 this also discusses experience with a DC treadmill motor.
I just hooked up a cheapo vfd on my little mill. My understanding is that there is a loss of torque at lower rpm. At the moment I do not remember who posted it but recently there was a post about repowering a lathe (?) With a larger motor to have the necessary torque at lower speeds. With time I will find out for my self. What i have found out is the torque and rpm drops to neer zero at max frequency of 400 htz. I have been testing it with 40 to 80 htz and found this to work so far. This applies to my setup, I realize other setups may be different.
Eric
The mill is from 1950's and is 3 phase German made.
I suspect that being German made and being old that the motor is designed for 50 Hz. it is probably not wise to run it above about 50 Hz or maybe 60 Hz maximum. The VFD sounds like a modern one with a max frequency of 400 Hz. That frequency is for the high speed spindles that have become available over the past few years, and it is not for normal lathe/mill motors.Quote:
Originally Posted by suther51
It sounds like your VFD is currently setup for a high speed spindle, if so then you need to re-programme it to a maximum frequency of 50 or 60 Hz or you will not get the best results. The voltage to frequency ratio will be way out if max freq is set to 400 Hz, the max voltage will be set to about 220/240 volts at 400 Hz, that means the voltage will be reduced to 27/30 volts at 50 Hz. If you set the VFD to a max freq of 50 Hz and max voltage to 240 v then you will have 8 times the torque.
In most cases it is probably safe to feed a 50 Hz motor with 400 Hz at the normal motor voltage as you have mentioned, the current will be low because of the motor inductance at that frequency, meaning that the torque will be low and with higher iron losses the torque will be too low to spin it up to the speed that would match the frequency. This seems to be what you have experienced.
On the other hand NEVER EVER run a 400 Hz high speed spindle on a VFD set to a max freq of 50/60 Hz. because at that frequency the spindle will be expecting a voltage of 27/30 v not 220/240 v. This will burn out your spindle motor quicker than you can reach the off switch once you see the smoke.
The post that you mention about using a big motor on a lathe is here http://www.homemadetools.net/forum/i...515#post135903
Thanks for the fast reply, Tony. My 2HP, 3ph lathe came with a new (at the time) RotoPhase converter and 5 HP motor. The lathe also has an antiquated mechanical, infinitely variable drive. Everything has been in storage for the past 30 years and not used. However, my understanding is that the old phase converters were quite noisy. Since I need to convert the lathe to single phase it would be nice to simplify the variable RPM drive. I was considering a VFD because it may be quieter and more efficient than the RotoPhase but also because it would simplify RPM changes. Your thoughts . . .
My thoughts. Firstly, many VFDs are noisy, those have a cooling fan which makes a lot of noise and is on all the time. I cured an ABB VFD by substituting a quiet computer fan which still runs all the time. More recently I got a Huanyang VFD which was even louder, I changed that for a computer fan, the original was 24 V but the computer fan is 12 V, so I used a series resistor. This is a very easy modification. Only last night I accidentally came across a video by Mark Presling (he also inhabits this forum so he might chirp in) about silencing a Huanyang VFD. His approach was somewhat different. He added a simple 45 deg bimetallic temperature switch such that the fan only comes on when the temperature of the internal heat sink gets to 45 deg. This morning I ordered some thermal switches, I think that the ultimate solution is Mark's switching and a quieter fan.Quote:
Originally Posted by Saltfever
There is another source of noise which generally afflicts some older motors. The PWM carrier frequency of VFDs ranges from around 2 kHz to over 10 kHz. Some motors will make a noise at that frequency which can be quite annoying. My ABB VFD drives a very old 1950s 5 hp motor on a shock dyno and there is no audible noise, I have not checked the carrier frequency. The Huanyang drives a 5 hp modern motor on my mill and there is no noise that I hear. The default frequency on that is 7 kHz but that is programmable up and down. However, if I use the Huanyang with the newly fitted 1990s motor on my lathe it whines. I made what is called a dV/dt filter to put between the motor and VFD which has cured it. In his video Mark mentions the same problem which he fixed by programming the carrier frequency to be higher. This is a very common "fix" but a word of warning. In general terms a higher carrier frequency is good for the motor but bad for the VFD because the IGBTs inside (electronic switches) generate more heat due to the increased switching.
About swapping the mechanical variable speed for a VFD, that should be fine unless you need to do heavy work at low speed, I have commented on this in earlier posts. Like my recent lathe motor change it looks like your lathe motor has gone from 2 hp to 5 hp which will be a big help.
About replacing the rotary converter with a VFD, I would not hesitate. the rotary converter will have a 3 ph motor inside which might be useful to power something else.
PS. here is a link to Mark's video https://www.youtube.com/watch?reload=9&v=x882vvX_L7Y
PPS. I will make post soon about making the dV/dt filter and generally filtering VFD/motor combinations.
-Thanks Tony - especially for the link to Mark's channel!
Cheers!
Johan
When is "soon" - as in the PPS? :)
A bit longer than "very soon".Quote:
Originally Posted by DIYSwede
Posting it right now, give me 10 minutes.Quote:
Originally Posted by DIYSwede
Yes, thanks . . . I understand that lower motor RPM = lower torque.Quote:
Originally Posted by tonyfoale
Sorry, my post was confusing and not clear. My RotoPhase (RP) has a 5 hp motor as part of the package. My lathe is still a 3 phase, 2 HP motor which I need to convert to 1 phase service.Quote:
Originally Posted by tonyfoale
If you note, the data plate indicates the RP sucks up 4 amps just at idle, no load! I was seeking quieter operation, higher efficiency, electronically variable RPM, and no loss of torque. I thought solid-state electronics could do that but I will loose torque and still have Hi Freq noise (about the same as the RP). Torque is important for my work so I may as well stay with the RP and the lathe's variable speed drive. I'm also considering buying a 3 HP, single Phase motor to make up for the HP loss when going from 3 phase to single phase.
So try 3 to succeed in posting.......
Thanks Tonyfoale for the information.
I currently have the max hz set at 100 or 80. I will.lower it, will.gave to try some settings and see what seems best under load, 60 or 50 max. Thanks again for the info. Hats off to all who post hard won knowledge to help others. The manual that came with the vfd is so incomplete it hurts my head. Status quo I understand for Chinese vfd's. I was real nervous for the first try ( some arrive doa I have heard) but all seems ok so far.
As a aside, the vfd's fan is thermally switched. I will see if i can post the "brand", many some pics if i have time to figure out how to post pics again.
Eric
https://rover.ebay.com/rover/0/0/0?m...2F283047413319
In the listing I do not see a brand name, will have to look at the manual.
Eric
That looks like a Huanyang copy. The widespread consensus is that the Huanyang brand is the best of the Chinese offerings and as a result there are many copies (chinese copying chinese) some of which are reportedly missing several features as well as reliability. I hope that yours is not in that class.Quote:
Originally Posted by suther51
That is only hearsay and I have no first hand knowledge of this. I have a German ABB which has worked fine since 2007 and a Huanyang which has worked fine since 2014. Neither have given any problems.
here is more VFD/motor stuff that I have just posted http://www.homemadetools.net/forum/s...s-motors-74010
