We got a replacement starting cap yesterday and @Tapper and I installed it, but it still didn’t work. Allen and @dallasmagna have also looked at the machine.
I don’t think its the breaker at the box because it doesn’t trip every time.
We pulled the motor and I emailed back the rep I was working with on the warranty, but he is out till Tuesday. I called the service desk to speak with another rep but the woodworking equipment department left at 4:30…I called at 4:32…damn day job.
So I will try again Monday.
All other tools in the woodshop are working, if they are not, please email [email protected]
The first thing they wanted us to do was try and replace the starting cap. We just did that yesterday and while it stays one about 1-2 seconds longer it still craps out. I don’t know much, hardly anything, about electrical motors though. I emailed the guy at powermatic back but he is out till Tuesday for what our next steps will be. I will post when I know more. I am hesitant to try and open the motor ourselves as I am sure that would void any warranty we currently have.
I work with and troubleshoot quite a few electrical pieces of equipment… A couple to things to look into and know…
The circuit breaker that the equipment is on… is it dedicated to that one piece of equipment or is it shared?
When did the problem start happening? Were there any other pieces of electrical equipment installed or added somewhere else in the shop around the same time? Anything change in the same time frame?
Before it trips… does it reach full speed or does it cut out as it is ramping up? It could be a problem with the motor starter windings.
Use an amp-probe/loop for AC Voltage and put it around the wires as close to the motor, as in no other devices between the meter and the motor, and note the amperage it pulls during the time it is spinning. Is it withing the rated amperage on the sticker of the motor or manual of the equipment? If it is over-amping it is a motor problem. Check the next step.
With it completely disconnected from power try moving/spinning the blade/motor. Does it spin freely or does it seem tight or tighter than normal? This would mean the motor has or will soon seize up completely if there is nothing physically preventing the blade/motor from spinning freely.
Going through these steps should identify the problem.
While it is ramping, that is what @dallasmagna believes as well.
notes from Chuck’s email to me from a previous day “I put an ammeter on one leg of the motor. It read above 100 amps briefly before the breaker trips, so there is definitely something wrong with the motor. Checked the windings with an ohmmeter. There is about 6 ohms across each phase. That seems like it might be Ok, but I do not know for sure. I checked for a short to the motor frame from any of the windings, and there is none (good).
There could be a problem with the start switch in the end bell of the motor, but to access it we have to pull the motor out of the machine (REALLY crap piece of design here). It will take more muscle than I can muster to get that honker out of there.”
After hearing about the saw dust build up and that the whole system probably over heated. We may have burned some of the insulation off some of the winding effectively lessening the number of winding and lowering the torque of the motor. Because of the lower torque motor we may be pulling more current in order to reach the speeds required thus tripping the breaker.
In RC cars you can get motors with less coils that have less torque but higher top end and motors with more coils which have higher torque but less top end. The low torque motors tend to draw a lot more current under stress and also get a lot hotter.
If everyone already knows this sorry for re-iterating as I’m an electronics newb. But, some times having a thought out failure case can lead to a test which proves or disproves it.
Thank for the work on this Alex and Chuck. I know problems with maybe solutions can be irritating.
After swapping out the startup cap, the motor fired up, ran up to what must have been very nearly full speed (but ramp up more slowly than usual), then blew the breaker. We tried again, and it ran up and stopped, but the breaker didn’t trip. Guessing that there’s a centrifugal switch to the run cap in the motor? Possible the switch to the smaller cap didn’t profide enough juice to run motor. Low torque? Breaker is 30A. After that, no more start. Guessing the start cap blew again, but showed no signs of it, and we didn’t do any further testing.
The motor is out of the housing now. The wiring is disconnected, but there’s a wiring diagram on the back of the cover plate. The red wire from the 208 supply goes to the 1-6 bundle, and the black goes to the 4-5 bundle.
The burned insulation theory matches my observations. Electrical expertise appreciated!
@mblatz, I don’t think they ended up using that cap. Chuck tried to use it, but it was slightly too large to use. @AlexRhodes ended up having one sent from the manufacturer.
