3hp Unisaw start capacitor? - Woodworking Talk - Woodworkers Forum

 
Thread Tools Display Modes
post #1 of 11 Old 01-08-2017, 11:12 PM Thread Starter
Junior Member
 
BThomas's Avatar
 
Join Date: Jan 2017
Location: Oregon
Posts: 10
View BThomas's Photo Album My Photos
3hp Unisaw start capacitor?

Hi All!

I have a 1979 Unisaw 34-771 with a re-motored Delta/Baldor 3hp 115/230v, single phase, 32/16Amp, 3450RPM motor. The motor is Delta number 83-651.

It's currently wired to run on 230v, 1ph power and has a magnetic starter. I've only had the saw a short time, and yesterday when I turned it on; it only hummed (no blade turn). I did some research, blew out the starter and motor, then I checked the start capacitor which was completely blown--guess I found my problem (hopefully).

The capacitor that was blown was a Vanguard BC-800. It's a 110/125V, 50-60hz, 829-995 MFD.

I noticed the capacitor was rated for 110/125V, which kind of surprised me as I thought that Start capacitors voltage was supposed to be higher than the line voltage, but I'm no technician or electrician so I've been looking everywhere to make sure that the next one I buy and put in is the correct capacitor.

Does anyone have better knowledge on this than I do???

Thanks a bazillion! And thanks for all the help you have given me the last few months while I was lurking!

Brent
BThomas is offline  
Sponsored Links
Advertisement
 
post #2 of 11 Old 01-09-2017, 08:02 AM
Moderator
 
Steve Neul's Avatar
 
Join Date: Sep 2011
Posts: 18,583
View Steve Neul's Photo Album My Photos
That capacitor I don't see how it's wired to 220v. Are you sure there is only one of them?
Steve Neul is online now  
post #3 of 11 Old 01-09-2017, 02:55 PM Thread Starter
Junior Member
 
BThomas's Avatar
 
Join Date: Jan 2017
Location: Oregon
Posts: 10
View BThomas's Photo Album My Photos
Quote:
Originally Posted by Steve Neul View Post
That capacitor I don't see how it's wired to 220v. Are you sure there is only one of them?
Yes Sir.... It makes me wonder if the previous owner was running it on 110v?

I bought it from a knowledgable third party who never used it. The rest of the saw/wiring looks correct. Here is a pic of it:
Attached Images
File Type: jpg image.jpg (72.0 KB, 30 views)
BThomas is offline  
 
post #4 of 11 Old 01-09-2017, 03:03 PM Thread Starter
Junior Member
 
BThomas's Avatar
 
Join Date: Jan 2017
Location: Oregon
Posts: 10
View BThomas's Photo Album My Photos
Quote:
Originally Posted by BThomas View Post
Yes Sir.... It makes me wonder if the previous owner was running it on 110v?

I bought it from a knowledgable third party who never used it. The rest of the saw/wiring looks correct. Here is a pic of it:
Here are more pics of what I have....
Attached Thumbnails
Click image for larger version

Name:	IMG_1050.jpg
Views:	14
Size:	62.1 KB
ID:	271466  

Click image for larger version

Name:	IMG_0681.jpg
Views:	18
Size:	97.5 KB
ID:	271474  

BThomas is offline  
post #5 of 11 Old 01-09-2017, 03:04 PM
where's my table saw?
 
woodnthings's Avatar
 
Join Date: Jan 2009
Location: SE, Michigan
Posts: 20,517
View woodnthings's Photo Album My Photos
What's the plug look like?

You had better start with the wiring diagram for that motor and see what's going on.



The plug will definitely tell you how it's wired. You did run it on 220 V right? Why would you suspect the previous owner, the one who actually used it had it wired for 120V? Did you rewire the plug end and did you convert the internal wiring to 220V?

Too many unknowns to did much advice.

The answer to your question will only be as detailed and specific as the question is detailed and specfic. Good questions also include a sketch or a photo

Last edited by woodnthings; 01-09-2017 at 03:06 PM.
woodnthings is online now  
post #6 of 11 Old 01-09-2017, 03:26 PM Thread Starter
Junior Member
 
BThomas's Avatar
 
Join Date: Jan 2017
Location: Oregon
Posts: 10
View BThomas's Photo Album My Photos
Quote:
Originally Posted by woodnthings View Post
You had better start with the wiring diagram for that motor and see what's going on.

The plug will definitely tell you how it's wired. You did run it on 220 V right? Why would you suspect the previous owner, the one who actually used it had it wired for 120V? Did you rewire the plug end and did you convert the internal wiring to 220V?

Too many unknowns to did much advice.
I am not an electrician, but I did receive it wired for 220 according to previous owner. I've checked the magnetic switches and it looks to me like it is wired properly when compared to diagrams I have showing 1 Ph, 220V. I also had it plugged into a 220v, 20amp circuit in my garage. I started it about 10 times, and ran a 6ft piece of 3/4" plywood through it before it stopped.

I thought it may have been wired for 120V because the start capacitor that blew was a 120V rated capacitor, not a 240V rated capacitor. I'm really trying to find out what start capacitor is supposed to be in this engine as I think the one I'm replacing may not be correct....

Thanks...
BThomas is offline  
post #7 of 11 Old 01-09-2017, 04:40 PM
Senior Member
 
Join Date: Feb 2016
Posts: 183
View Brian(J)'s Photo Album My Photos
Quote:
Originally Posted by BThomas View Post
I am not an electrician, but I did receive it wired for 220 according to previous owner. I've checked the magnetic switches and it looks to me like it is wired properly when compared to diagrams I have showing 1 Ph, 220V. I also had it plugged into a 220v, 20amp circuit in my garage. I started it about 10 times, and ran a 6ft piece of 3/4" plywood through it before it stopped.

I thought it may have been wired for 120V because the start capacitor that blew was a 120V rated capacitor, not a 240V rated capacitor. I'm really trying to find out what start capacitor is supposed to be in this engine as I think the one I'm replacing may not be correct....

Thanks...
I'm not an expert with motors, but have worked a lot with them over the last 40 years.
Let's look at what exactly the capacitor is and what it is doing. At the dam, a rotor spins past magnets which wired up in three sets- A, B, and C. Each set is called a Phase and connected to a wire, so you have three wires coming from the dam, A phase, B phase, and C phase. When the wires get to your shop, you connect each wire to one of the three in your 3 Phase Unisaw motor and you are good to go ( I'm simplifying this just a tiny little bit). The direction the motor will spin is easy, it will spin A B C just like back at the dam. If you want it to spin the other way just change it to A C B. So simple.
Problem is, you've got Single Phase, which is just two of those wires. When you connect the motor to A and B, it has no way to know which way to go, so it just sits there and vibrates, while getting hot.
In a Capacitor equipped motor the capacitor is wired onto one of the phases, in your case both are 120v phases. The capacitor acts like a bucket for the electrons. The effect of that is to make the power from the capacitor phase 'late' getting to the motor, because it had to fill up with electrons and that took time, allowing the motor shaft to rotate more into the opposite phase's pole (magnet). Having filled up (charged) the capacitor with electrons, now the capacitor discharges but the motor shaft has rotated enough that this discharge is now 'pushing' the shaft in the direction you want.
This entire process is called 'lagging' and most likely takes place on only one of the two 120 volt phases. So a 120 volt capacitor is probably fine.
Brian(J) is offline  
post #8 of 11 Old 01-09-2017, 04:49 PM
Senior Member
 
Join Date: Feb 2016
Posts: 183
View Brian(J)'s Photo Album My Photos
Quote:
Originally Posted by BThomas View Post
I am not an electrician, but I did receive it wired for 220 according to previous owner. I've checked the magnetic switches and it looks to me like it is wired properly when compared to diagrams I have showing 1 Ph, 220V. I also had it plugged into a 220v, 20amp circuit in my garage. I started it about 10 times, and ran a 6ft piece of 3/4" plywood through it before it stopped.

I thought it may have been wired for 120V because the start capacitor that blew was a 120V rated capacitor, not a 240V rated capacitor. I'm really trying to find out what start capacitor is supposed to be in this engine as I think the one I'm replacing may not be correct....

Thanks...
Also, and I am dreading getting into this because of the endless discussions of 120v vs 240v wiring for table saws, any motor that can be hooked up to 120 or 240 has ONLY 120 volt components. These are hooked up in series for 120v and parallel for 240v, the motor sees only 120v. You can run 240v to the wiring box on the motor but after that it is 120v all the way. It is possible to get 240v into the motor itself, it will burn out in a very short time, under a minute.
Brian(J) is offline  
post #9 of 11 Old 01-09-2017, 05:49 PM Thread Starter
Junior Member
 
BThomas's Avatar
 
Join Date: Jan 2017
Location: Oregon
Posts: 10
View BThomas's Photo Album My Photos
Thank you Brian. That really helped me understand this better. You did a better job explaining that than the motor repair guy did a few minutes ago. He also told me the 120 is correct and sold me another sc for $18. I'll go plug it in and try again.

Thanks to you and everyone who reached out to help me--really appreciate it!
BThomas is offline  
post #10 of 11 Old 01-09-2017, 06:46 PM
Senior Member
 
Join Date: Jan 2016
Posts: 174
View Catpower's Photo Album My Photos
Quote:
Originally Posted by Brian(J) View Post
Also, and I am dreading getting into this because of the endless discussions of 120v vs 240v wiring for table saws, any motor that can be hooked up to 120 or 240 has ONLY 120 volt components. These are hooked up in series for 120v and parallel for 240v, the motor sees only 120v. You can run 240v to the wiring box on the motor but after that it is 120v all the way. It is possible to get 240v into the motor itself, it will burn out in a very short time, under a minute.

Actually they are in series for 240 and parallel for 120, not a big deal, unless you put power to the windings in parallel with 240, then you will let out the magic smoke pretty quick
Catpower is online now  
post #11 of 11 Old 01-09-2017, 07:02 PM Thread Starter
Junior Member
 
BThomas's Avatar
 
Join Date: Jan 2017
Location: Oregon
Posts: 10
View BThomas's Photo Album My Photos
The saw runs again! Hopefully it keeps going! Thank you!!!
BThomas is offline  
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Woodworking Talk - Woodworkers Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in









Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Similar Threads
Thread Thread Starter Forum Replies Last Post
unisaw vs griz Wally Caritj Power Tools & Machinery 11 05-20-2016 07:26 PM
Freebie Air Compressor No Start Lute Power Tools & Machinery 10 04-28-2016 04:52 PM
Electric motor problem need help finding a capacitor ZenBaker Power Tools & Machinery 7 01-18-2016 09:11 AM
Delta 36-725 tripped my circuit breaker. Now the saw won't start. Any help? unknowneinstein Power Tools & Machinery 7 01-03-2016 07:10 PM
How To Start New Topics (Threads) Cricket Getting Started With WoodworkingTalk 0 12-07-2015 01:50 PM

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

 
For the best viewing experience please update your browser to Google Chrome