PowerPro Anomaly

[DLB]

This started as an annoyance and has graduated to nuisance. I picked up a used and extensively modified 510 that included a DIY PP headstock. My plan was to use the PP headstock on my shorty, build a mini from that conventional headstock plus other leftover parts, and sell my power station and all the leftovers. More power for all. That has not worked out. Early on I was balancing the belts and when I selected 9500 RPM the machine accelerated into the 6K - 7K range followed by the 0 range. Display was uninformative, it said the RPM was low but I had already noticed the quiet and not spinning. The behavior wasn't 100% repeatable and only occurred at a speed range I rarely use. It seemed to occur much less often if the machine was warmed up before selecting high speed.

In the last couple of days I was trimming a blank interior door panel in length and width. I used an almost new thin kerf fine finish blade which I know is not ideal for ripping. But I think the machine should have handled it. I repeatedly got the same symptoms as above, quiet, no spinning, and low RPM message. Interestingly I could press ON without CONFIRM and it would spin back up. Feeding at anything like a reasonable feed rate would again stop it.

For now, I'm just wondering if anyone else has seen this. When I first saw a PP demo Mike ripped a board about 10X faster than I would feed it without a hickup. It didn't leave a particularly clean cut, but he was demo'ing the PowerPro not the right way to make a cut. Because I know the saw setup wasn't ideal and it's the same symptoms, I'm focusing mainly on spinning up to 9500 RPM with nothing on the spindles.

- David

[edma194]

There is clearly something wrong, a PowerPro should have no problem ripping a board even with a thin kerf blade (assuming you are not binding the blade somehow). I think you should start by checking the speed sensor as with an RPS 0 problem:

https://www.shopsmith.com/mediawiki/ind ... o_Problems

[DLB]

There is clearly something wrong, a PowerPro should have no problem ripping a board even with a thin kerf blade (assuming you are not binding the blade somehow). I think you should start by checking the speed sensor as with an RPS 0 problem:

Thanks Ed, I did do that while it was still just an annoyance. I didn't have any RPS error message, but I removed the fan and cleaned both it and the sensors and re-installed the fan with thread locker. I used both compressed air and alcohol on the sensors. It made no difference. One day I even swapped the motor, also no difference. So I'm thinking it has to be in the Power Supply. A bad connection might make sense, but changing the motor reseats the important ones. I would think it is weird that it is getting into a fail state without a true failure message. I also tried it on 120V, mostly because it was easy.

- David

[edma194]

These things scare me. There's no diagnostic mode that we know about and just a little bit of information in the wiki. I just looked at the section on the DOES NOT ROTATE message in the wiki, what on earth is going on there?

What version of the software do you have? Have you contacted Shopsmith about this? Do they offer to help in any way?

[DLB]

These things scare me. There's no diagnostic mode that we know about and just a little bit of information in the wiki. I just looked at the section on the DOES NOT ROTATE message in the wiki, what on earth is going on there?

What version of the software do you have? Have you contacted Shopsmith about this? Do they offer to help in any way?

The software comes up as v9.08csa16 2011. I haven't contacted Shopsmith. I'll read through that wiki CS document again and see if I see something useful. 'Low RPM' is fairly intuitive, but not one of the seven most common error messages in the Troubleshooting section of my DIY manual.

- David

[DLB]

Through part swapping I've confirmed that this anomaly is caused by the Power Supply module. (Which I think contains much more functionality than the name implies.)

- David

[DLB]

My best guess now is that the 'failure message' ("Low!" where I should see actual RPM) I'm seeing is probably indicating the overload protection has tripped.

There is a vague reference to overload protection in the SS Wiki PowerPro Problems document: "RESPONSE FROM JIM: Does the AC drive have current limiting protection? Yes it has current limiting protection combined with thermal protection. " Nova and Rikon documentation also reflects the existence of overload protection but I have not found how it is communicated to the user.

I have the PowerPro components on the bench and I'm using a rag and gripping the motor pulley to vary load. At all speeds this system trips at ~4.5 Amps of AC input current (back on 120 VAC for this). It seems obvious that if this is indeed the overload protection it should be occurring at a much higher value, a minimum of 15 Amps or perhaps a bit higher to allow for transient conditions.

- David

[JPG]

If I were monitoring for over current conditions with a stepping motor, I would be observing current to the motor coils. Not something we can easily do here.

P.S. your current measurements taken using what device, and at what input voltage?

[DLB]

If I were monitoring for over current conditions with a stepping motor, I would be observing current to the motor coils. Not something we can easily do here.

P.S. your current measurements taken using what device, and at what input voltage?

I was monitoring both the AC in and one of the motor drives. AC Amps in on 120 VAC with a DMM with clamp-on ammeter. Motor drive on an oscilloscope with a clamp on amp probe. The drive current is pulsed, pulse waveform varies with speed, I was using pulse amplitude and measured ~3.6 Amps at the trip point, independent of speed. Current on both AC In and motor drive increase uniformly in response to mechanical load until they trip. There are six current drive wires to the motor, for now I'm assuming that maps to three phases of current drive with independent returns. I have just one current probe for the scope. There appear to be eight current drive pulses per revolution per line.

Note - I was quoting Jim (McCann, likely) in that statement regarding AC Current Limiting protection, from the last part of this: https://www.shopsmith.com/mediawiki/ind ... em_Solving The other sources mentioned overload protection, which may or may not be the same thing. There could also be multiple overload protections.

- David

[edma194]

Note - I was quoting Jim (McCann, likely) in that statement regarding AC Current Limiting protection, from the last part of this: https://www.shopsmith.com/mediawiki/ind ... em_Solving The other sources mentioned overload protection, which may or may not be the same thing. There could also be multiple overload protections.

- David

And thermal protection is specifically mentioned:
" Yes it has current limiting protection combined with thermal protection. As the power supply reaches critical temperature it will automatically chop the current, limiting the power and reducing torque. You will also see a message on the screen stating "INVERTER OVERHEAT". Then, if you don't stop the machine the power supply will completely shut down until it cools sufficiently to reset and be started again."

It should produce that message but a temperature sensor problem might be triggering the condition, possibly allowing stray pulses which the control logic can't handle gracefully. I have no idea how to check on that thermal sensor though. Since the error message is INVERTER OVERHEAT I would think that the sensor is found in the power supply module.