Conversion of a mini import step pulley drive lathe to a variable speed motor?

[Glen Perye]

Has anybody done this with the motor controller set up, that PSI sells for the mini lathe imports. I have been told that they aren't worth the money. Also if some body has done this any suggestions for motor or controller for a DC motor set-up. I'm currently thinking and researching a Sherline set up, as the lathe and mill I have are great.

 

[jschnell1203]

I originally bought the PSI lathe w/o variable speed and found it a pain changing speeds so I bought the VS motor upgrade. It works fine for small light stuff like pens/bottle stoppers but for small bowls/plates it overheats/stops. I put the original motor back in again. I'm going to use the moter on my rose engine machine. Also I bought another PSI lathe with VS and the same issues with larger pieces.

 

[billooms]

I bought the PSI VS motor (for use with my rose engine) and the speed controller went up in smoke within a year. They were kind enough to replace it at no charge, but I replaced it with a Sherline motor while I was waiting for PSI to respond. Now, the PSI motor is set aside and I only use it for doing demos so I don't know if the replaced speed controller is any better.

 

[Patrick Miller]

done it

I bought a Turncrafter Pro with step pulleys and later purchased PSI's variable speed package- cost $100.00 at the time. It works OK with some caveats-
1) If I run at a low speed with a load for 10 minutes or so the thermal overload will kick out and I have to let the thing set for a bit, push the reset button on the control box and go again.
2) The slowest speed even in the slow belt setting was still too fast for me, around 500rpm. It seems like the new motor came with a 3 step pulley installed versus 5. I took the 5 step pulley from the old motor and put it on the new motor with the smallest motor diameter lined up with the largest spindle pulley to give me a slower speed closer to 300rpm.
The convenience was worth 100 bucks to me but not much more. I did use the original motor as a polishing buff unit so there was that plus also.

 

[Bill Turpin]

I did the PSI conversion about four years ago. Works good. I turned a 8" bowl from S. Red maple with it. Was able to use original step pulleys which yielded a slower slow speed. Be sure to make a centering block as per instructions BEFORE tearing lathe apart.

 

[Bill Boehme]

The biggest problem with their design is that the motor is not designed to run at slow speeds under heavy load for any significant length of time. On DC motors, speed is a function of applied voltage and current is a function of output torque. The motor attempts to maintain speed under heavy torque load by increasing current. The problem here is that when running at slow speed the motor is not being cooled by its internal fan and very quickly overheats. If the controller were a better design, it would have a more robust current limiting circuit, but it does not. Even under the best conditions, the power output at the low speed end is marginal for anything except small items.

 

[Glen Perye]

Thanks that is what I needed to know. I will check into the Sherline and also considering a tread mill motor and controller. Since that also was recommend by a number of people on a general shop forum.
I will only be doing small stuff on the mini, and have an old Delta with a 1hp motor if I decide to do any heavy large stuff.

 

[Tony Pinkus]

Vicmarc variable speed

I have an early Vicmarc VL100 with a simple on/off switch, unidirectional and which I would dearly like wish to convert to variable speed bidirectional. Vicmarc offered me a motor upgrade with variable speed at more than I paid for the lathe. I guess there is an easy solution? I do have a variable 0.5hp 3 phase digital inverter knocking around which may be part of a solution?

Any advice would be welcome.

Thanks

Tony

 

[Tim L]

I bought the VS motor from PSI to upgrade my Jet mini a year ago and have had no problems. I really love it. I usually do smaller stuff so I don't know how it would work with a 8-10 in bowl.
Tim.

 

[Syd Sellers]

VFD For 3 Phase Motors

I have an early Vicmarc VL100 with a simple on/off switch, unidirectional and which I would dearly like wish to convert to variable speed bidirectional. Vicmarc offered me a motor upgrade with variable speed at more than I paid for the lathe. I guess there is an easy solution? I do have a variable 0.5hp 3 phase digital inverter knocking around which may be part of a solution?

Any advice would be welcome.

Thanks

Tony

Hi Tony, I have installed speed controls on my lathes, bandsaw and press drill with a small box of electronics made by KB Electronics Controls.
KB Drives, KB Electroinic Drives, KB Speed Controls, KB Accessories
They are based out of Florida.

If you can work with Electrical items and wire things, you can make yourself very nice variable speed drives for all your machines.
I was able to find old used 3 Phase motors at a great price and put this VFD on them. The same box of electronics will provide Variable speed and Forward and Reverse. You plug this unit into standard 120 Volt single Phase power and it produces 220/440 volt 3 Phase power for the motor.
The only draw back is that they produce RFI and your radio will complain a whole lot....

Check it out, they cost around $170.00 each.
Syd.

 

[Patrick Miller]

I have an early Vicmarc VL100 with a simple on/off switch, unidirectional and which I would dearly like wish to convert to variable speed bidirectional. Vicmarc offered me a motor upgrade with variable speed at more than I paid for the lathe. I guess there is an easy solution? I do have a variable 0.5hp 3 phase digital inverter knocking around which may be part of a solution?

Any advice would be welcome.

Thanks

Tony

Tony- A while back I converted a Jet 1236 using a 1HP Boston Gear DC PM motor and a Graham Cycletrol C2000 drive. Simple DPDT switch to provide reversing (full stop before switching). I had access to the motor for no $ and the drive was around $100.00 on eBay. Worked fine for me although some one with a bit more knowledge could probably have set the drive parameters so the start and stop was not quite so abrupt. I simply turned the speed control down before I turned on the lathe which from a safety stand point is a good idea regardless. I have used the exact same set-up on my drill press- very handy.
have fun-

 

[Tony Pinkus]

Vicmarc lathe variable motor speed implant

Hi Syd and Patrick

Many thanks for your advice. I should have said I'm in the UK so we are on good ol 240v ac and this changes things for motors and suppliers. But the advice is relatively similar.

I have a three phase inverter with a variable rheostat and a 1/2w capacity output so I will check to see whether the Vicmarc motor terminals have both star and delta terminals so that I can switch to the three phase and use the for running under variable 3 phase

Meanwhile I came accross what might be the simplest answer and cheapest from China. http://www.ebay.co.uk/itm/New-50V-2...Bikes_GL&hash=item4d06cb4776&autorefresh=true

 

[Bill Boehme]

If your current motor is single phase, it can't be used with an inverter. You will need to get a three phase motor. It would be best to get one that is rated for inverter duty. If it isn't, it may gradually die over time or maybe just decrease in performance until you eventually decide that it is no longer providing adequate power for what you need.

 

[Tony Pinkus]

Variable speed for lathe motor

Thanks Bill

Much appreciated, I've read your excellent and very comprehensive postings on this subject and accept what you say above. It's no accident,, and very convenient, that we have single phase 240v and you guys have multiphase 220v. Apparently, 90% of the motors available in the UK under 5HP these days are dual rated, so that they can readily be sold into the US market as multiphase phase 220v with a simple change to the wiring configuration from delta to star. Hence my question about this use of a converter in a previous post. I guess in the US a different maxim applies.

One question I have outstanding is in regards to an efficient solution to converting this old Vicmarc from solely belt change to bi directional variable speed without a second mortgage!

From your article I appreciate that to control an ac motor speed and retain the torque you need a device to vary the frequency from 0-50Hz so that the current and voltage are the same. Even then the motor may not spin fast enough to cool the windings so there is an inherent risk.

There are many options being touted to control single phase ac motors over here. Can I use a simple light switch dimmer of sufficient power rating (ie 650w) or a Pulse width Modulation speed controller to vary the motor speed of a single phase ac motor? I guess varying the resistance alone may not give me the torque but what about the Pulse width controller below? Because for a few cents this sure seems like an economical solution!

Warm regards

Tony


Details of SCR AC Motor Speed Controller with Knob 50-220V10A
[*]Control the speed of a AC motor with this controller
[*]High efficiency, high torque, low heat generating
[*]With reverse polarity protection, high current protection
[*]Working Voltage: AC 50V to AC 220V
[*]Maximum power:2000w
[*]Static Current: 0.02 A ( Standby )
[*]Duty Cycle: 10% -100%
[*]Frequency: 13 KHz
[*]Size (L x W x H ): Approx. 73 x 60 x 27 mm
[*]Material: Plastic, metal
[/LIST]

 

[Bill Boehme]

... It's no accident,, and very convenient, that we have single phase 240v and you guys have multiphase 220v. Apparently, 90% of the motors available in the UK under 5HP these days are dual rated, so that they can readily be sold into the US market as multiphase phase 220v with a simple change to the wiring configuration from delta to star. Hence my question about this use of a converter in a previous post. I guess in the US a different maxim applies.

Over here residential power is single phase 240 VAC with center tap for 120 VAC which most things such as lighting and small appliances use. Large appliances and machines such as ovens ranges, dryers, and large shop machines use 240 VAC, but it is all single phase.

Industrial electric service is typically three phase since large three phase motor are less expensive to build and in addition are much more efficient in converting electrical power to mechanical work.

Single phase induction motors actually have two phases that are electrically 90° out of phase. The phase shift comes from having a capacitor connected to the secondary winding to create the phase shift since it is not available from the supply. This means that any AC electric motor of appreciable size used in the home workshop will have a start capacitor and may also have a run capacitor. Motors for small handheld tools like drills and routers do not require this because they are universal motors -- meaning that they are actually DC motors that by virtue of their design are able to run on either DC or AC.

I was not familiar with the term star, so I Googled it and found that it is the same thing that we call "Wye" (for its shape like the letter Y). Delta (Δ) and Y are the to types of three phase configurations. A Y configuration is used when a neutral wire is required. Whether Δ or Y configuration, the voltage at the three terminals are shifted by 120° electrical degrees from each other.

At this point I remain a bit skeptical about any motors being able to operate on either single phase or three phase because the basic configurations are so different, the internal space for stuffing wiring in a motor is at a premium, and the rotor configuration would need to be different for efficient operation. I won't say it can't be done, but I can't imagine why it would.

BTW, over here the term "dual rated" generally refers to configuring the motor to operate on either 120 VAC or 240 VAC and not single vs. three phase operation.

One question I have outstanding is in regards to an efficient solution to converting this old Vicmarc from solely belt change to bi directional variable speed without a second mortgage!

Any AC induction motor can be changed to run in either direction with a DPDT switch although some motors are more difficult than others to make the mod depending on the accessibility of certain wires. Tell me more about the motor on your lathe. Does it have a start capacitor? How about a centrifugal switch (you can tell if it has one if it makes a click sound as the motor coasts to a stop after turning off the power)? How many wires are connected to the motor? Are any of them connected to the motor frame?

I can't help with the mortgage, but in order to use an inverter (AKA, variable frequency drive), a three phase motor is necessary.

I am not familiar with that model lathe and it might be possible that it is an universal motor although I suspect otherwise. controlling the speed of universal motors is much simpler than it is for AC motors, but the downside is that efficiency is much lower and speed regulation is not very good under varying load conditions.

From your article I appreciate that to control an ac motor speed and retain the torque you need a device to vary the frequency from 0-50Hz so that the current and voltage are the same. Even then the motor may not spin fast enough to cool the windings so there is an inherent risk.

Basically, that is correct. However, the voltage does not remain at the full supply voltage level as the speed is decreased. The reason that the voltage is decreased as the speed is decreased is because we do want to magnetically saturate the iron core of the motor. A term called magnetic reluctance is analogous to electrical resistance. The reluctance of the iron decreases as the frequency of the applied AC power decreases. This means that the voltage has to be reduced to the level that the maximum current does not go higher than it would when running at full load and rated speed. Output torque is directly proportional to motor current.

There are many options being touted to control single phase ac motors over here. Can I use a simple light switch dimmer of sufficient power rating (ie 650w) or a Pulse width Modulation speed controller to vary the motor speed of a single phase ac motor? I guess varying the resistance alone may not give me the torque but what about the Pulse width controller below? Because for a few cents this sure seems like an economical solution!

The light dimmer won't work on AC induction motors. The reason is that the dimmer varies the voltage, but AC motor speed is controlled by frequency. If you hook one up to an AC induction motor, it would be a toss-up as to which will go up in smoke first.

However, the light dimmer type control is very similar to the type of speed controls use to vary the speed of DC universal motors. That is the way that variable speed drills and routers work. Also, some mini lathes use DC universal motors with this type of control because of the low cost. The downside is that at low speed, they also have very low torque output.

The pulse-width modulated variable frequency drive is the way to control AC motors and as I previously mentioned, the motor has to be a three phase type.

 

[Tony Pinkus]

Vicmarc variable speed conversion

Thanks Bill for your, as always, detailed
I am still abroad on business in Bali, where the wood is fabulous - (teak trees everywhere! and no woodworking machinery younger than 1950s) so have not as yet collected my Vicmarc VL100. I do have a photo of it though to satisfy your curiosity. It is basically the first and best constructed and specified mini-lathe on the market. I have one already with a variable speed drive but the 'spare' below is an older machine with a manual speed change option only.

Taking up your suggestion above, I notice there are a host of inverter drives on the market and these need to be programmed to suit the motor. Is this a simple job? I note that some go up to 1000Hz which might be interesting in relation to maximum speed and torque!

Warm regards

Tony

 

[Bill Boehme]

Thanks Bill for your, as always, detailed
I am still abroad on business in Bali, where the wood is fabulous - (teak trees everywhere! and no woodworking machinery younger than 1950s) so have not as yet collected my Vicmarc VL100. I do have a photo of it though to satisfy your curiosity. It is basically the first and best constructed and specified mini-lathe on the market. I have one already with a variable speed drive but the 'spare' below is an older machine with a manual speed change option only.

Taking up your suggestion above, I notice there are a host of inverter drives on the market and these need to be programmed to suit the motor. Is this a simple job? I note that some go up to 1000Hz which might be interesting in relation to maximum speed and torque!

Warm regards

Tony

That is a really nice looking mini lathe, Tony. I believe that one of the members in my turning club also has the same model lathe and also converted it to variable speed using an inverter and three phase motor.

Yes, there are a huge number of inverters on the market and also covering a considerable price range. As you might guess, the more expensive ones have more features, better performance, and are easier to set up. I'll briefly touch on the three basic categories of drives for three-phase induction motors.

Volts per Hertz

The least complex and lowest cost type of inverter for three-phase induction motors is the Volts per Hertz type, usually abbreviated V/Hz. It is primarily intended for constant load applications where the speed may change, but the output torque is fairly constant. An example application would be a conveyor moving products along an assembly line. This type of controller is usually only found on smaller motors of 2 HP or less. Also, this type of controller has about a 10:1 speed range or less. However, the motor performance must also be considered when determining the operating speed range. In the real world, the minimum speed is typically about 20% of the base speed of the motor. Below that, speed regulation is often too poor to be useable.

The designation V/Hz means that the voltage supplied to the motor varies proportionally to the frequency. As mentioned previously, this is done to prevent magnetically saturating the iron. This type of inverter does not monitor speed or current to make corrections to the motor so speed regulation is not very good at the lower end.
​

Sensorless Vector

Sensorless vector inverters are basically V/Hz inverters which have the capability to indirectly estimate the actual motor speed and then correct the output to the motor to improve speed regulation. Typical speed range with a suitable motor is about 33:1.

This type of inverter measures output current to the motor. That, along with known motor parameters, enables the controller to estimate the slip frequency of the motor. Slip frequency is the difference between the commanded speed and the actual sped of the motor. This method of estimating speed without an actual speed sensor is the reason for the designation "sensorless". This method works well at moderate speeds and faster, but at the slower speeds, the low sample rate causes the speed regulation to degrade. Realistically, one could expect the slowest speed to be about 5% of base speed given the right motor paired with the inverter.

This type of inverter is often easier to program than the basic V/Hz inverter. It also is more expensive.
​

Vector Control

This type of inverter is the most sophisticated by far (as well as being the most expensive by far). It uses a speed sensor attached to the motor -- typically an optical encoder that outputs a digital signal providing both shaft position angle and shaft rotation speed. This type of inverter can provide speed regulation of 0.1% or better from zero speed up to the maximum limit of the motor. Using an optimal motor/inverter combination enables it to provide full rated torque from a standstill up to base speed -- and rated horsepower above that up to the maximum speed allowed.

This type of inverter typically is fully automatic when going through the set up procedure to "tune" its performance to match the motor characteristics. The menus on the LCD display are in plain language and easy to navigate. It can also fix breakfast and wash the dishes.
​

Setting up the inverter for optimal performance the motor and load varies from being mostly manual for low end inverters to being fully automatic for the top of the line vector inverters.

Concerning the unit that spec'd 1000Hz, there are two different frequencies to consider. One is the carrier frequency of the PWM signal and the other is the synthesized power line frequency. The carrier frequency is normally in the range of 1kHz to 10 kHz. Low end inverters typically operate at lower frequencies. The output power frequency range typically varies from 2 Hz to 200 Hz.

 

[Alan Van Art]

See my Flickr set (http://www.flickr.com/photos/alanv/sets/72157630019126798/) to view how I converted my Benchmount VIcmarc VL100 to to a 1hp 3 phase reversible variable speed motor. In my case I have 110v single phase input voltage, but this is merely a function of the inverter.

 

[Bill Boehme]

See my Flickr set (http://www.flickr.com/photos/alanv/sets/72157630019126798/) to view how I converted my Benchmount VIcmarc VL100 to to a 1hp 3 phase reversible variable speed motor. In my case I have 110v single phase input voltage, but this is merely a function of the inverter.

I'm surprised that the motor and inverter have not burned up in those enclosures.

 

[Marvin Hasenak]

Industrial sewing machine motors have the controller units built in to them. DC motor, 3/4HP, more than enough power for a mini lathe. Around a $100 on eBay.