What is this and why is it smoking?!

[Dan Hahr]

Well, I just finished refurbishing a Delta X5 planer and started it up. It ran a few seconds and then I smelt electrical smoke. I shut it down and opened up the box. The photos show what I found.

Are those cylinders capacitors or magnetic switches or what? It looks like some lead looking stuff has melted out of the one on the left. It was also quite warm. I see no other evidence of any shorts.

The planer was very rusty as it had sat in an open garage for years. It is only five years old. Could moisture cause this problem? If not, I will need to contact Delta as it is just barely out of warranty.

Do I need to buy an new switch or can this one be repaired?

Thanks, Dan

[Steve Clardy]

Yes. It smoked a capacitor.

Replace it with the same capacity, 400MDF or whatever yours is.

I smoked one on my 4hp collector last year. It just gave up I guess.

[David DeCristoforo]

"What is this and why is it smoking?!"

That's exactly what my wife wanted to know the first time she saw me....

[Tom Veatch]

...The planer was very rusty as it had sat in an open garage for years. It is only five years old. Could moisture cause this problem?...

This is strictly a guess, but it looks like the start capacitor has been fried. They are easy and fairly cheap to replace. The question is why did it fail?

Start capacitors are intermittent duty devices. They are intended to be energized only during the start cycle of the motor. A centrifugal switch should open and de-energize the capacitor when the motor reaches about 75-80% of it's rated RPM. That switch operation is the "click" you often hear shortly after you start and/or stop a capacitor-start induction motor. If the switch fails closed so that it doesn't open at the proper time, less than a minute of motor operation is generally enough to fry the capacitor.

Your planer has sat in an open garage for up to 5 years and is very rusty. Look for that switch to be rusted shut. If it is, the replacement capacitor will also be ruined shortly after being replaced. Check, clean, and repair or replace the centrifugal switch in the motor.

[Michael Weber]

"What is this and why is it smoking?!"

That's exactly what my wife wanted to know the first time she saw me....

pretty bad David.

[Chip Lindley]

My Thoughts Exactly!! Opening the motor is not a huge deal. The *fan* end usually comes right off after removing the external fan blade, and undoing the four long bolts. Separate the front bell from the windings, and the stator can be removed. Leave the pulley and front bell intact on the stator shaft. No need to mess with it.

Once the fan-end of the stator is in view, you will see how the centrfugal switch slides up and down the shaft under spring pressure. A cleaning of the shaft and a squirt of dry teflon lube is in order so it slides nicely. Don't lose any shim washers which may be in the bearing cup of the end bell. Make note of how you take it all apart, and re-assemble in reverse order (with NO parts left over) *grin*

Checking this start winding switch is good insurance before you install and power up a new capacitor! This motor appears to have both start and run capacitors. You know the start cap. is fried, but the run cap. may also need replacing, if the motor still will not power up.

[David G Baker]

Be careful with the dry Teflon lube. Before you use it make sure that all of the old lube is cleaned off the shaft. I have had items seize up after accidentally mixing spray Teflon or spray silicone with grease type lubes.

[Chris Tsutsui]

This is obvious, though make sure you connect the new caps with the right polarity.

One time I did it wrong and a cap exploded on me.

Basically I got sprayed with clear juice that got all over the place and I saw a mini white mushroom cloud of smoke rise through the air above the cap.

[Tom Veatch]

This is obvious, though make sure you connect the new caps with the right polarity.....

Chris, remember we're working with AC.

[Dan Hahr]

OK The large capacitor has START CAPACITOR printed on it and is a 500uF cap. The little one is the 20uF cap and is fried. I guess that is the run cap.

I really appreciate the advice on the motor switch and will check it out. Any good online sources for motor disassembly instructions? It's probably easier that it sounds. I took the end off and dusted off the fan. Other than the end of the shaft, the rest looks spotless, but I did not mess with the movement. I will let you know.

Thanks again, Dan

[Ken Fitzgerald]

Dan...typically there is just a cover on the end of the motor that requires a couple of screws removed and the switch is under that cover. It is attached similarly as the points were on old car ignitian systems. Centrifigual force operates them.

[Dan Hahr]

I just went out and looked at it. The shaft is slightly rusted. The metal switch that springs out when spun is clean and was held to the shaft with one screw. When stopped, the switch pushes what appears to be points closed, but the way it is wired, it seems that it opens the connection.

I started to take the three bolts out to take the cast iron end off but with the switch/points connected to it, I decided to wait to see if it was really necessary. Everything is clean inside. The switch seems tight, but only beacuse of the spring tension. I suppose some lubrication would help a little.

I believe the the motor was never subject to direct rain, but it was probably subjected to blowing mist whenever it rained and was windy. I don't see how the water would blow the capacitor by itself. That box was sealed quite well.

Do I need to further investigate the internal workings of the motor?

Thanks, Dan

[Tom Veatch]

I just went out and looked at it. The shaft is slightly rusted. The metal switch that springs out when spun is clean and was held to the shaft with one screw. When stopped, the switch pushes what appears to be points closed, but the way it is wired, it seems that it opens the connection...

If the switch is clean and can be moved without binding, then most likely it's OK. And your observation about the switch opening the connection when running and closing the connection when stopped is the correct operation for the switch.

What's interesting, and a little surprising, is that it's the run capacitor that's damaged. If that's the case, an undamaged start capacitor is even more evidence that the switch is OK. I've had several start capacitors go bad, but never a run capacitor - yet! It's possible, maybe even likely, that over the years there was enough deterioration (corrosion?) in the capacitor to develop a internal short which would cause it to self destruct almost immediately (a few seconds, you said).

It's entirely your choice, but in your shoes, I'd put the motor back together, replace the run capacitor and switch it on. It probably won't blow a second time, but if it does, then I'd pull the motor and have it bench checked at the friendly neighborhood motor shop.

[Richard Wagner]

OK The large capacitor has START CAPACITOR printed on it and is a 500uF cap. The little one is the 20uF cap and is fried. I guess that is the run cap.

I really appreciate the advice on the motor switch and will check it out. Any good online sources for motor disassembly instructions? It's probably easier that it sounds. I took the end off and dusted off the fan. Other than the end of the shaft, the rest looks spotless, but I did not mess with the movement. I will let you know.

Thanks again, Dan

This is a really easy task; however, there is one trick I have learned that helps reassembly. BEFORE you disassemble the motor, mark the motor housing and the end caps so that you can reassemble them in exactly the same positions (with respect to one another). I use a small center punch to create a permanent alignment mark.

[Chris Tsutsui]

Chris, remember we're working with AC.

Tom, polarity may not apply to these particular caps, but just because you are working with AC doesn't mean you shouldn't have your precautions...

I should mention that was working with AC when the caps exploded on me... There was one rather large cap.

I found out that in the frequency of 50/60Hz, they can use 2 poloarized caps (with capacitance doubled of the non-polarized cap) connected in series by opposite terminals (and diodes in parallel with each cap to protect it from reversed voltage) to replace 1 non polarized cap to save space.