Jet 1642 losing power

[Kevin Bierman]

I have a 8-10 year 1 1/2 hp Jet 1642 I lent it to a buddy when I was on vacation and had not used it very much, doing flat work for Christmas, and have started turning again. The lathe runs fine, gets up to speed ok, but when I put a tool to a piece of wet wood I can stop it very easily. Checked the belt, it is tight does not slip. Found out my buddy tried to use it in his garage with GFI plug ins, that didn't work and I think he might have messed with the inverter, he wouldn't fess up. I talked to Jet service dept. and they want me standing next to it when I call, work days so having a hard time making that go. I did take the motor in, it checked out fine. Any one have an idea?

[Steve Schlumpf]

Kevin - do you still have the manual for the VDF? If so, check on how to do a reset. I have the 220 volt version and my manual says to just press the reset button after a fault to reset the VFD. Might be as simple as that...

[Len Mullin]

Kevin, have you learned anything from this experience? Personally, I'd never loan my lathe to anyone. I worked to long and hard to get the funds to buy it, you want to use one, buy your own. Granted I will allow people use my lathe, but, they have to use it in my shop while I'm present. If I'm not there, no one uses any of my equipment. Think long and hard before lending it again, that might help prevent these types of problems from happening.
Len

[Don Palese]

Hi Kevin,
When I had my 1.5 hp - 1642 -- I had a similar situation .. I don't think this is common at all and I really don't understand it .. but it seem the circuit break was going bad and when more load was calling on more juice .. it would just never recover until I stopped the machine and pressed the reset on the VFD. (no more demand on the breaker) I replaced the breaker with a new one and never had the problem again. I really would have preferred to have the breaker just totally fail. I sent it to GE the manufacturer but never heard back.

[Kevin Bierman]

Thanks for your replies, as far as loaning out tools, yeah it does seem like no good deed goes unpunished. I guess it is just in my nature not to say no to someone in need. some day I will learn. The lathe is the only big tool on that circuit so think I will try a different circuit before I get the manual out and start messing with the settings in the VDF. Thanks again will press forward, Kevin

[Dan Hintz]

Kevin, have you learned anything from this experience?

Who says his buddy was the one who broke it? Things do fail on their own...

[Bill Boehme]

Who says his buddy was the one who broke it? ....

You borrowed it? :D

[Dan Hintz]

You borrowed it? :D


I'll never tell!

[Dick Strauss]

Does Jet lock the VFD settings like they do for PMs? If so, your buddy would have a hard time changing settings unless he found the unlock code online.

[Kevin Bierman]

Dick..... I would have thought the same thing but when I talked to Jet service they didn't seem to think it couldn't be done. I really hope it is just a weak circuit breaker. Will get to play with it this weekend. Kevin

[Bill Boehme]

Here is one possible scenario for decreased motor performance when driven by an inverter. The PWM waveform that inverters use to synthesize sinusoidal output results in very large voltage spikes that can be well in excess of a kilovolt. That is why it is strongly recommended that motors rated for inverter duty be used. Generally, that means motors that have windings that have an insulation class rating of F, G, or H. It would be a concern if the motor insulation class isn't rated for inverter duty.

The problem often shows up as gradually decreasing motor performance that may stretch over many months which makes it harder to notice than a sudden failure. The cause of the failure is that the high voltage spikes penetrates through the insulation of the field windings usually where the wires make a sharp bend at the ends of the lamination stack. When this happens, the breakdown in insulation occurs between adjacent wires so the decrease in performance is slight. The problem is that there is an avalanche effect because each insulation breakdown puts an increasing load on the motor to maintain speed and torque.

Because these insulation breakdowns are typically microscopic, a visual examination probably won't reveal anything. I hope that your problem is something else.

[John K Jordan]

Pardon the simplistic question, but could your buddy have switched the belt to the high-speed position, reducing the torque?

If you want to check the VFD parameters and can't find them, send me a note by email and I'll send them to you. The first thing I did when I got my 1642 lathe was step through every parameter and write the values in my VFD manual.

BTW, if you don't have one the Delta Electronics VFD manual is available online as a PDF file. It won't have the Jet 1642 parameters though.

JKJ

[Bill Boehme]

Pardon the simplistic question, but could your buddy have switched the belt to the high-speed position, reducing the torque? ....

But, can't we run Kevin through the wringer a couple times before checking for more obvious things?

[Dick Bernard]

I have a Jet 1642, the 1 1/2 hp. Please be advised that I know "nothing" about electricity and/or electronics.
My question is, why is that VDF needed and more importantly, why are there different settings or, what would you use the different settings for or, when would you change the settings?

Is there a common setting?
As an example, could Joe in Montana use setting 4 (as an example) as well as Jim in Florida???

Thank you
Dick

[Josh Bowman]

Dick Not to get off topic with Kevin's question. But to answer your question, there are maybe 3 ways to control speed of a motor, belts and lots of pulleys, reeve drive (mechanical split pulley), VFD (Variable Frequency Drive) converts the incoming AC to DC and in the case of the Jet converts it back to a 3 phase signal that can vary the frequency, thus the speed.

Kevin, I'm with John Jordan, check if the belt is on the high speed pulley and tight. Let us know what you find.


I have a Jet 1642, the 1 1/2 hp. Please be advised that I know "nothing" about electricity and/or electronics.
My question is, why is that VDF needed and more importantly, why are there different settings or, what would you use the different settings for or, when would you change the settings?

Is there a common setting?
As an example, could Joe in Montana use setting 4 (as an example) as well as Jim in Florida???

Thank you
Dick

[John K Jordan]

My question is, why is that VDF needed and more importantly, why are there different settings or, what would you use the different settings for or, when would you change the settings?

Dick, that is an excellent question. Josh already gave the main reason, to provide a speed control for the lathe without using a mechanical method. There are other electrical means to change speed but converting to 3-phase gives wide range, excellent torque, and allows the use of generally much less expensive 3-phase motors.

The parameter settings in the VFD control many things. The VFD is actually a general-purpose device that can be used in a huge variety of mostly industrial applications. The parameters define the motor, amperage, speed limits, and many other things. There is almost nothing that you would want to change, in fact, most changes could make the lathe quit working or even damage things. One change that wouldn't hurt anything is the acceleration parameter. For example if you always turned heavy blanks you might change the acceleration/deceleration time from 5 seconds to something longer. But ANY messing with the parameters can mess things up if you do something wrong - kind of like messing with the registry of your computer except the result of a goof might be more spectacular!

If you want a feel for the complexity of the programming, look through the manual of the VFD that is on your Jet 1642:
www.shopbottools.com/ShopBotDocs/files/ (http://www.shopbottools.com/ShopBotDocs/files/)VFD-S_manual_en.pdf (http://www.shopbottools.com/ShopBotDocs/files/VFD-S_manual_en.pdf)

Learning how to program one of these can be handy, however. A few months ago one of my Jet 1642s died - the VFD croaked inside, dead, gone. An identical replacement is VERY expensive. But since these VFDs are general-purpose you can actually use one of VFDs on the market, IF you can get it wired up and programmed correctly. I dived into this with the help of Harvey Meyer who had replaced one on his PM3520. It was less than 1/3 the cost of the Delta. A bit (well, a lot) of studying, some wiring, and some programming and the lathe now works again. It appears to me the programming on various brands is basically similar but different in detail and terminology so you can't just copy the parameters from one to another. But there is no magic, just mystery and technology!

One thing a bit disturbing I discovered with all this: it looks to me like Jet chose to reduce the power of the 1-1/2 hp 1642 to 1 hp. The VFD they used is rated at 1 hp and the parameters for the amount of current supplied to the match up with 1 hp. I suspect they did this because 1) who would check, 2) the 1 hp VFD is a lot cheaper than the next larger one, 3) they found the life of the motor was shortened at the higher rating, 4) the wall plug requirements were less, or maybe 5), the lathe itself was not quite sturdy enough to handle the higher hp for extended use. Who knows. This was disturbing at first, but then I realized that I have not once stalled my lathes or felt limited by the power.

When I bought a replacement VFD I got one rated higher than 1 hp (for several reasons) but chose to program it to the power rating that Jet used.

BTW, looking at the programming of the new VFD I think I can add a feature that might be useful - a switch to change the acceleration. This way I could have the lathe spin up and down quicker when working on small things and make it spin up more gradually if turning a larger blank. This would require me to not accidentally have the switch in the wrong position!

JKJ

[Bill Boehme]

John, the cost difference between a VFD rated for 1HP versus a VFD rated for 1.5 HP couldn't be much considering that the basic V/Hz Delta inverter they use is just about a bottom of the food chain model. I think that the real answer is something else like maybe the motor isn't the world's greatest. It's possible that the motor isn't rated for inverter duty so derating its operating conditions is a way to prevent early failure. Another thing to consider is that if you are using a motor not rated for inverter duty then the speed range is severely restricted to approximately a 5:1 range ... in other words, the minimum speed would be about 360 RPM. By derating the output power, the speed range could be expanded to 10:1 ... meaning that the minimum speed could be as low as 180 RPM.

Also, the motor is not able to be operated above base speed. At first glance that might not seem to be a big deal, but that actually this would allow a designer to change the pulley drive ratio to have the peak power in a mid-range area that would match operating speeds most commonly used by woodturners. This would also have the benefit of enabling slower minimum spindle speeds than otherwise possible.

I think that Jet is being wisely conservative if the above assumptions are accurate. However, in the real world when using very slow speeds we typically aren't loading the motor down so I think that it would be safe to go slower if we keep these things in mind. Since these V/Hz inverters are running open loop, the low end speed varies a lot with torque load.

[John K Jordan]

the cost difference between a VFD rated for 1HP versus a VFD rated for 1.5 HP couldn't be much considering that the basic V/Hz Delta inverter they use is just about a bottom of the food chain model.

Yeah, you'd think. But when I checked they wanted about $600 from me for that low-end model! I didn't check on the larger Delta.

When I bought the different and much less expensive brand to replace the dead one I THINK I remember the difference was about 30% more to go from the 1 hp to the 2 hp model, the next largest one in the line. Knowing just a bit about how the industrial economy works 30% would be a big consideration.

JKJ

[Larry Copas]

I converted an old Rockwell to a 3-phase motor and VFD. My motor was 1 ½ HP. My choices for a VFD were a 1 HP model or a 2 HP model. I chose the 1 HP model because it only required a 115V input while the 2 HP model required a 230 V input. I didn't have a 230 V circuit and didn't want to run a new one. Saved a few dollars also.

When I checked specs my motor only exceeded my VFD output by just a couple tenths of an amp. When I checked my VFD specs it can be ran at 150% rated current for 1 minute. 200% over current instantaneous.

With about a year of use my VFD has never shut off so I guess I've never went past the limits. BTW I love the conversion. I've ran it so slow it hardly turns for sanding.

Thought maybe my explanation might shed some light on what Jet does.

[Kevin Bierman]

I did not get a chance to play around with a different circuit this past weekend like I had hoped. will try and get that done soon. If that does not make any difference I will just have to make time to be home during the week and get with the Jet service tech. I appreciate all the advice from all of you, but man you are talking way over my head, just do not have experience with these sort of things. I am starting to think my friend did not get into the VFD or the lathe wouldn't run at all. I did try changing the speed range but that didn't make any difference. will start a new post if and when I get this figured out. Kevin