3 phase motor on Jet 1642 lathe

[Gregg Feldstone]

I'm planning to buy the Jet 1642 evs 2hp lathe. I was looking at the manual online and noticed that it has a 3 phase motor. Talked to someone knowledgable at Woodcraft and found out it has a built in phase converter (or a VSD) , so it runs on single phase 230v. What I don't know is, WHAT KIND OF PHASE CONVERTER DOES IT USE? I'm thinking it is probably a VSD , being it's a varialbe speed machine and can go in reverse. I'm no electrician or engineer, so I did a little research and found out that VSD's have some drawbacks. One that concerns me is a tendency to burn out the motor if operated at very low speeds frequently ( due to the cooling fan running too slowly). I also read that the vsd's need to be oversized to handle changing loads. It sounds like a rotary phase converter is more reliable, especially the new "Boost" and other models which provide plenty of start up power and continuous monitoring of load. I'm hoping the Jet lathe has this but I have my doubts. Can anyone help me with these questions? Also, how do the Oneway and other machines wich are variable speed but have single phase motors achieve said variable speed? I know it can't be a rayostat, as the voltage is lowered to slow down the motor, providing no torque......such as on my mini-lathe. Thanks for your help!!

[Jim Davenport]

in simplistic terms, A basic "VFD" works by converting AC Input to DC. It then uses a transister inverter network to pulse a variable voltage and frequency output. The VFD's on the jet, and PM lathes take a single phase input, and the inverter section of the drive generates the third leg.
VFD's are a viable option to run small three phase motors in a shop with single phase power. They are readily available on "E-pay".

[Gregg Feldstone]

Anybody up late who has an opinion on this??

[David Parker]

Hi Greg,

I recently bought the Jet 1642 EVS 2 HP lathe, but still need to have a 30 amp 230 volt outlet installed in my workshop. So it's sitting there patiently waiting for power.

It comes with a Delta VFD-S AC motor drive (model VFD015S21U). An extensive manual (on CD) is included with this VFD. It is preprogrammed by Jet for use with their motor and they caution you not to change the settings. This device has an output of up to 7.5 amps, 2.9 KVA, and 2 HP (1.5 KW).

Looking through the manual, most of it is beyond my meager understanding.
Control system - Sinusoidal Pulse Width Modulation, carrier freq 3-10KHz
Output frequency resolution - 0.1 Hz
Torque characteristics - including the autotorque, autoslip compensation; starting torque can be 150% at 5 Hz
Overload endurance - 150% of rated current for 1 minute
Acceleration/Deceleration time - 0.1 to 600 seconds
Adjustable VF pattern
Stall prevention level - 20 to 250%, setting of rated current

The manual does recommend a 30 amp circuit breaker for this device. From what I can tell, this is a very capable VFD and how it performs with the motor has more to do with it's programming than with it's limitations.

Dave

[Jim Becker]

Most true variable speed lathes these days use a VFD controlled 3-phase motor including the Jet 1642. The VFD does the phase "conversion" and also controls the speed by varying the frequency (in hertz) of the power flowing to the motor. Hence the name, Variable Frequency Drive.

You will find that you'll have more than enough torque to do the job with the lathe and most also have two or three ranges you can adjust to by moving the belts. My 2hp Stubby 750, for example, has two ranges and I typically use the slower range 99% of the time. It provides 0-1200 RPM and at "almost not turning" I almost cannot stop the machine from turning without the belt slipping.

[M Toupin]

Gregg,
Don't get too wrapped around the axle here. It's a VFD, variable frequency drive, not a VSD, and it's integral to the lathe. It's a 3 phase motor cuz the VFD takes 22v 1 phase power and converts it to 3ph to drive the motor. This allows all those cool things like variable speed and reverse. You don't need to do anything but plug it into a 220v single phase outlet. The lathe will take care of the rest. Yes, you "can" burn up a motor with a VFD by running it too slow and not moving enough air to cool it. The neat part about a VFD is you can program the high and low limits and this limit the min and max hertz (speed). I can assure you Jet has already done this and undoubtably was more than generous. The last thing Jet wants is a few 1000 customers burning up the motors. jet doesn't want that bad publicity nor do they want to replace all those motors.

Mike

[Fred Conte]

Gregg the advice you got from the other folks is right on. I have never heard of a 3 ph vfd controlled motor burning up going to slow. Besides being a wood turner I turn and cut metal too. Alot of the guys on the metalworking forums I belong to have converted their metal lathes and mills to VFD and love it especially for turning threads in steel at low rpm and HIGH torque or diving into a hunk of steel with a 3/4" end mill.
Fred

[Dick Strauss]

Greg,
There are two differnet kinds of motors you can use. I'm sure that Jet and PM use inverter duty motors exclusively for their VFD lathes. As Mike states, I'm sure Jet has done their homework!

Inverter Duty Motors
The inverter duty motors for VFDs (variable frequency drives) are overbuilt with respect to cooling (and over-voltage situations). They don't need the fan to turn at full speed to keep the unit cool. They rely more on natural convection rather than forced convection. In fact, many inverter duty motors are not TEFC (thermally enclosed/fan cooled) once you get beyond 2-3hp. High hp inverter duty motors are TENV (themally enclosed/non-vented) and rely solely on natural convection along with lots of metal mass in the case to better dissipate the heat buildup.

Standard Duty Motors
A standard 1.5 horsepower three phase motor can overheat from too slow of a fan speed because it relies more on the fan for cooling.

Here's some more info for you:
http://www.automationdirect.com/static/specs/motorsselection.pdf

I hope this helps!

[John-Paul Murphy]

Hi Greg
I have the 1.5 hp 1642.
It is equipped with a Delta S1 series (you can check them in the net. They have all the bells and whistles as do most drives these days) Pulse With Modulated variable frequency drive. It has a belt to change between two speed ranges. I will try to stay away from to much technical stuff but what happens is if a motor gets to hot the insulation melts and the motor fails. If a 2 horse power lathe is being used to spin a pen it will not use the full 2 horsepower. Only enough to spin the pen, lower horse power usage = less heat to dissipate = not as much fan needed. On the opposite end if you are spinning a 31 x 42 in block of heavy wood at a low speed and feeding heavy with a gouge then way more horse power is needed. The drive and motor will try to provide the power to meet demand. More power demand = more heat to dissipate = more fan needed.
I have run my lathe for as much as 6 hours (with rest in between for me) the motor was and is always no more than a little warm to the touch.
In order for a VFD to vary the speed of an AC motor it must be a 3 phase motor(at least in my experience). The VFDs can be designed to take a variety of phase and power inputs and still create the required 3 phase output.
I checked the Oneway site, though they may take a 1 phase input the VFD outputs 3 phase to the motor.
Ps I got the 1.5 because it was a great deal and I could plug it into a standard 110 outlet. I am very happy with my lathe though I have not had the opportunity to thoroughly test many varieties.
2nd PS my motor is not an “inverter” duty motor though it is an “E” class.

[Reed Gray]

I have had my PM 3520A for 8 years, and have used it a lot. It has the Delta converter. I spend as much time sanding as I do turning, maybe more. When I sand, I have the speed down to 20 rpm or less because my bowls are all warped. The converter and motor are still running strong, although I did wear out one set of headstock bearingsl
robo hippy