5HP MOTOR WITH RUN CAPACITOR
5HP MOTOR WITH RUN CAPACITOR
(OP)
Please be patient with me,
We have an older 16" Dewalt Radial arm saw we use for building pallets. On three separate occasions now, we have blown the run capacitor out of the mounts. Motor was recently taken to rewind shop and had the end bells machined because of damage form bad bearings. We had thought this was the suspect to the capacitors blowing. However once again we let the magic oil and smoke out. The motor in question is a 5hp 230 single phase. My direct question is there is a small transformer looking item in the pecker head, wire in series with the cap. Is this in fact reducing the voltage to 120V? In addition, I would like to hear your interpretation on how a run capacitor functions in the motor and what could cause it to blow.
We have an older 16" Dewalt Radial arm saw we use for building pallets. On three separate occasions now, we have blown the run capacitor out of the mounts. Motor was recently taken to rewind shop and had the end bells machined because of damage form bad bearings. We had thought this was the suspect to the capacitors blowing. However once again we let the magic oil and smoke out. The motor in question is a 5hp 230 single phase. My direct question is there is a small transformer looking item in the pecker head, wire in series with the cap. Is this in fact reducing the voltage to 120V? In addition, I would like to hear your interpretation on how a run capacitor functions in the motor and what could cause it to blow.





RE: 5HP MOTOR WITH RUN CAPACITOR
JRaef.com
"Engineers like to solve problems. If there are no problems handily available, they will create their own problems." Scott Adams
For the best use of Eng-Tips, please click here -> FAQ731-376
RE: 5HP MOTOR WITH RUN CAPACITOR
With respect, JRaef, I see a lot of potential relays on refrigerators and small hermetic units in general, but I have not seen one on a saw motor.
Are you sure that the capacitor is not a start capacitor? Run capacitors are becoming more common on air conditioners but I don't often see them on saw motors, particularly older saws.
Transformer to 120 volts? Not enough space in the junction box for a large enough transformer.
Function of the run capacitor? Power factor correction and incidentaly transient surge suppresion. The capacitor doesn't affect the motor directly but does reduce the current somewhat with the result of slightly higher voltage to the motor. The exception is a permanent split capacitor motor, but 5 hp. seems a little large for a PSC motor. What do you say JRaef. Have PSC motors gotten larger without me seeing them?
The fact that there is a device in series with the capacitor also suggests a probability that it is a start capacitor.
respectfully
RE: 5HP MOTOR WITH RUN CAPACITOR
I thought of either a OL device or maybe even a braking device, but he said it is wired in series with the capacitor and that is the only thing I could see being in series that way. I know what you mean about not seeing potential relays on saw motors, but I have seen them mentioned in a number of machine tool and wood working DIY forums of late touted as a way of replacing worn out centrifugal switches. Seems to be a sort of sub-culture solution to the fact that older motors are beginning to get difficult to repair because the manufacturers are consolidating and not supporting old designs. By the way, I was thinking of a Cap-Start Cap-Run 1 phase motor, which is what you often see in the 5HP range as far as off-the-shelf motors go.
2571,
Here is one of the types of articles I was referring to regarding 1 phase motor options. Scroll down to the Capacitor-Start Capacitor-Run design, that is what I think you may have if you have a set of caps labels as "Running" caps. If you just thought they were running caps and didn't really know for sure, they might be starting caps as waross said, shown in the Capacitor-Start Induction Run design.
http:
JRaef.com
"Engineers like to solve problems. If there are no problems handily available, they will create their own problems." Scott Adams
For the best use of Eng-Tips, please click here -> FAQ731-376
RE: 5HP MOTOR WITH RUN CAPACITOR
They started with manual brakes. You had to push the mechanical brake on the motor.(I have one.) Then they went to automatic ones based on relay stuff.
Also 5Hp on a single phase RA saw?!?!? Sounds about 2X bigger than I could ever imagine. A 5 HP single phase motor is HUGE. I run an air compressor with a 5HP 1ph motor - it weighs almost 200 pounds and is 20" in diameter and 25" long. Maybe Dewalt went the way of Sears and blatantly lies about the actual HP though.
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: 5HP MOTOR WITH RUN CAPACITOR
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Note that the brake is mechanical.
JRaef.com
"Engineers like to solve problems. If there are no problems handily available, they will create their own problems." Scott Adams
For the best use of Eng-Tips, please click here -> FAQ731-376
RE: 5HP MOTOR WITH RUN CAPACITOR
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: 5HP MOTOR WITH RUN CAPACITOR
I bought a Shop-Vac the other day which stated "5.5HP, 14A" on the box, it's 120-volt single-phase with a standard 15-amp plug.
Turns out that 5.5HP is a "peak" rating (but you gotta dig to figure that out)... and that's about the only way you'd ever pull 5.5HP out of a 15-amp 120-volt single-phase plug. I'm not quite sure exactly what "peak" HP is defined as, but I imagine you're pulling close to LRA when you see "peak" HP, and I suspect that if you divided the "peak" HP by 6 or 7 that you'd be a lot closer to a real (continuous) HP number.
I suspect a lot of motorized consumer goods are advertised by their "peak" HP rating.
RE: 5HP MOTOR WITH RUN CAPACITOR
JRaef.com
"Engineers like to solve problems. If there are no problems handily available, they will create their own problems." Scott Adams
For the best use of Eng-Tips, please click here -> FAQ731-376
RE: 5HP MOTOR WITH RUN CAPACITOR
RE: 5HP MOTOR WITH RUN CAPACITOR
Sears started with these blatant lies about 10 years ago and now many others have jumped on the wagon. I should really take this to our District Attorney who hates this kind of false advertising and actually prosecutes about 3 of these type cases a year against various national suppliers.
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: 5HP MOTOR WITH RUN CAPACITOR
Apparently this has been done already though. This link is to a Google html version of a pdf, the original of which is gone now (Google stores the html search version longer apparently). It describes a class action lawsuit brought against Campbell-Hausfeld, deVilbiss et al on this very issue.
[link http
Just in case Google drops it now that the original is gone, here are the salient points.
JRaef.com
"Engineers like to solve problems. If there are no problems handily available, they will create their own problems." Scott Adams
For the best use of Eng-Tips, please click here -> FAQ731-376
RE: 5HP MOTOR WITH RUN CAPACITOR
Hmmm I wonder why they persist in false advertising.
Thanks, I must read it all.
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: 5HP MOTOR WITH RUN CAPACITOR
respectfully