Thread: Is this capacitor problem?

Can you make it run the other way, i.e start with the motor off and then spin the motor the other way and see if it starts and continues in that same direction.

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Originally Posted by BobL

Can you make it run the other way, i.e start with the motor off and then spin the motor the other way and see if it starts and continues in that same direction.

Hi BobL, I have only tried with belt off the main wheel and it works fine without any load on it but when the drive belt is put back on the main wheel it will not drive it. It seems to start and run fine with the drive belt off, It's only a 2 hp motor.

SB

With the belt on, the saw blade off, and the power turned on give the big wheel a spin. If it runs then it is the capacitor which has lost capacitance and doesn't give the starter winding enough of a kick to overcome the load.

Just be careful that you don't get caught by the wheel suddenly taking off.

Also check that the saw blade wheels spin freely to ensure that you don't have a sticky bearing as well.

Originally Posted by Bohdan

With the belt on, the saw blade off, and the power turned on give the big wheel a spin. If it runs then it is the capacitor which has lost capacitance and doesn't give the starter winding enough of a kick to overcome the load.

Just be careful that you don't get caught by the wheel suddenly taking off.

Also check that the saw blade wheels spin freely to ensure that you don't have a sticky bearing as well.

Thanks Bohdan, just what I was after, some way to do a simple check if the symptom was not an obvious guide to the problem. I'll give it a go with safety upper most. At the end of the day it is still under warranty but now I'm living in the rural setting it’s a big job to take it into town when it might be something simple.

SB

Could the problem be that your off grid supply can't provide the starting current required by the saw?
especially if the house is running a heavy load -- e.g. washing machine and/or air con

Originally Posted by ian

Could the problem be that your off grid supply can't provide the starting current required by the saw?
especially if the house is running a heavy load -- e.g. washing machine and/or air con

Yes, the off grid fallacy raises its head again. Sorry to say my system has no problems running my workshop what so ever, there’s plenty of power. I do have a gold standard system I must say. It has run the bandsaw for the last 6 months with no problem. Anyhow the house is not connected yet only the workshop. It also runs my 3hp table saw with no problem, but thanks for the suggestion Ian, it might be a problem lesser off grid systems.

SB

Originally Posted by Superbunny

Yes, the off grid fallacy raises its head again. Sorry to say my system has no problems running my workshop what so ever, there’s plenty of power. I do have a gold standard system I must say. It has run the bandsaw for the last 6 months with no problem. Anyhow the house is not connected yet only the workshop. It also runs my 3hp table saw with no problem, but thanks for the suggestion Ian

don't you mean "HAPPY to say ..."

in terms of problem solving, my own experience with remote area power is that starting currents and unbalanced loads can play havoc.
I'm sort of following your house build and thought that about now you might have connected the house to your solar system -- and as such the house load could have been the difference between now and when the saw last started without problems.
Glad that you can rule out problems with the supply. so it looks as though you have isolated the issue to something within the saw's electronics.

Originally Posted by ian

don't you mean "HAPPY to say ..."

in terms of problem solving, my own experience with remote area power is that starting currents and unbalanced loads can play havoc.
I'm sort of following your house build and thought that about now you might have connected the house to your solar system -- and as such the house load could have been the difference between now and when the saw last started without problems.
Glad that you can rule out problems with the supply. so it looks as though you have isolated the issue to something within the saw's electronics.

Yep, your right Ian, it should be happy to say. The house should be connected in a couple of months we hope. The off grid was designed by professionals with the knowledge of my workshop machinery and house loads.

SB

When you fix it change to a setup that has a variable Hertz line. You want one that has 50-60Hz not be a fixed 50Hz or 55 Hz or whatever.

I spent a lot of my life off grid, mostly diesel generator systems. The issue with small systems is that start up loads tend to cause a frequency drop. Fixed Hz line capacitors will handle this for a bit until the day comes when they wont. If its the capacitor you'll probably have to replace the potential relay as well.

After a bit it just becomes second nature to check the Hz line on everything electrical you buy, and store weenies give you the look when you go to buy a new fridge or cut off saw and say "Whats the hertz???"

Originally Posted by Superbunny

My Jet 18” Bandsaw will not go, it's only 3 years old and has not had much use to date. It will not move the blade at start up. I took the belt off from the motor to the bottom wheel pulley and switched it on, the motor runs fine. So I'm thinking it's a start capacitor problem as it not starting under load. Can anyone confirm this or should I start looking at another area for the problem.

SB

My table saw has the same symptoms.the capacitor was shot, to test the capacitor you can test the resistance value for high resistance or o/c,
OR (carefully ,using an insulated screwdriver),short across the terminals with the power unplugged.if it bangs it maybe OK,if not, it's not charging up.they cost about $15 to replace
be sure to match the micro farad rating
Diclaimer I'm a tech not an electrician

How does the capacitor look? Often it will be swollen or leaking, a good indication that it's shot.

I had a capacitor failure with my Hammer bandsaw. It was cheaper & quicker to source a replacement from a supplier of air conditioner parts.

John G - If it's a solar system, it'll have an inverter, which doesn't suffer Hz drop during start-up. Generator systems do, because the frequency is maintained by the momentum of the generator rotor - bigger loads cause it to vary.

Biggest problem with inverter systems is not having the required overcurrent ability - their weakness is overheating.

Inverters that go into overload due to startup currents should throw a warning - you can tell if you hit the go button on your load and your inverter screams - sometimes it's a two person operation to check. They also sometimes don't have the ability to increase their output fast enough to let the load kick over in the manner in which it was designed. That can kill your start capacitor as it takes a bigger hit for longer as the motor effectively "soft starts" due to a voltage dip. Superbunny would notice this because his lights would dim down and the inverter (should) throw an undervoltage alarm.

The cap could have been shot by repeated long, slow starts. Or it could have been a marginal unit in the first place.

Either way, sounds like a capacitor issue. Giving a wheel the flick to start the motor up is a pretty easy way to tell if the start winding is not doing much. If the winding is totally busted, it'll never turn itself over without at least a little kick (normally a big kick). If the cap is the problem, then the lack of starting torque, but ability to spin itself at a lower load is generally a giveaway.

Starting cap is the easiest and cheapest thing to test if you want to start swapping out parts.

Of course, all this ignores Bohdans quite wise suggestion to spin the wheels without a belt attached (and the power off!) and make sure that they all spin freely. If a bearing has thrown it's toys in the first 6 - 12 months, I'd be hitting the supplier up for a warranty call where they just send you a replacement for the busted part - no way I'd be dragging a BS around the country for that.

Well it's been a long time, I know, I know. Well after over 6 months I eventually got around to pulling the motor off and taking it in for repair at my local Carbatec, believe it or not it had a 3 year warranty and I only had a couple of weeks left before it runs out.

I got it back the other day and put it back in and all works well. They could not tell me what was wrong as the repair shop didn’t say what the problem was.

themage21 is right but I don't have a problem with my off grid as it was designed by professionals with my workshop needs taken into consideration and it can cope with all my machinery no problem, I run a 3hp 15amp saw table with no problem and the bandsaw is 2hp 10amp and runs with a dust extractor at the same time easy.

Anyhow, given all the effort and help you guys have given me, I thought the lest I should do is update and say thanks for your help.

SB