Thanks: 0
Likes: 0
Needs Pictures: 0
Picture(s) thanks: 0
Results 1 to 4 of 4
-
21st August 2009, 01:34 PM #1
Of induction motors and starting capacitors
Let me get the formalities out of the way firstNo liability is accepted by UBeaut or the Wood Working Forum's administrators
DISCLAIMER
or moderators for advice offered by members posting replies
or asking questions regarding electrical work.
We strongly advise contacting a Licensed Tradeperson for all electrical work.
WARNINGInformation supplied within posts is not to be considered as detailed formal instructions to complete a task.
Members following such information do so at their own risk
So, that should shorten this thread appreciably!
The other day I was using my 8" long bed jointer, a Woodman with 2hp motor (made in Taiwan 1991), bought s/h, when without warning it stopped dead.
No strange noises, no magic smoke, nor expensive smells. On checking the RCD (this thing has a 15A plug) it had tripped.
Time to investigate, putting the multimeter across the input plug revealed a dead short between active and neutral. Inspection for physical damage to the cord, both outside and inside the cabinet, revealed no problems.
Time to further investigate. The 2hp motor is an induction motor with a big capacitor, again putting the multimeter across the active and neutral input terminals on the motor revealed a dead short.
Opening the cover over the, rather large (85mm long x 45mm diam), capacitor pointed to a very likely cause. The top of the capacitor had come off completely, revealing a smelly mess. It was a 400mfd, 125V capacitor, first phone call to an electric motor place struck gold, they had one in stock same electrical specs and same physical dimensions, mine for $20.
When I queried the guy on the 125V bit, he told me that it was quite normal for start capacitors to have this voltage rating, in fact he showed me a brand new 2hp motor on the shelf that had the same capacitor.
Coming home, installed new capacitor (after changing connectors from lug to female spade), fingers crossed switched on and bingo, worked like a bought one.
At least I didn't have to buy a new motor
-
21st August 2009 01:34 PM # ADSGoogle Adsense Advertisement
- Join Date
- Always
- Location
- Advertising world
- Age
- 2010
- Posts
- Many
-
21st August 2009, 02:12 PM #2SENIOR MEMBER
- Join Date
- Nov 2008
- Location
- Sydney
- Age
- 93
- Posts
- 570
You did the right thing, Big Shed. The 'dead shorts' could have depended on what Ohms scale you used with your multimeter.
-
21st August 2009, 02:42 PM #3
I understood capacitor and something-or-other volts. The rest, well that's why I get a sparky.
Replaced one myself on the b/saw and
My knowledge of things that go zap, ended at about grade 8. Not to say I haven't gone zap a few times though.
Disclaimer: don't try and go zap yourself.
-
22nd August 2009, 02:29 AM #4Electrician
- Join Date
- Sep 2007
- Location
- Thailand
- Age
- 62
- Posts
- 192
Big Shed.
Just out of curiosity, what are the details of the motor (rating plate info)?“I do not think there is any thrill that can go through the human heart like that felt by the inventor as he sees some creation of the brain unfolding to success... Such emotions make a man forget food, sleep, friends, love, everything.” - Nikola Tesla.
Similar Threads
-
induction motors
By HUON in forum BANDSAWSReplies: 2Last Post: 14th September 2008, 11:49 AM -
Capacitors
By arose62 in forum Links to: TOOLS & MACHINERYReplies: 2Last Post: 13th March 2008, 10:53 PM -
Induction Motor- Saw
By boxers in forum HAND TOOLS - POWEREDReplies: 2Last Post: 2nd April 2006, 01:52 PM -
Capacitors for single phase motor
By boban in forum HAND TOOLS - POWEREDReplies: 21Last Post: 2nd June 2005, 05:45 PM -
Starting Single Phase Electric Motors
By silentC in forum NOTHING AT ALL TO DO WITH WOODWORKReplies: 6Last Post: 9th February 2004, 07:17 PM