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Run versus Start Capacitors - How to tell



 
 
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  #11  
Old April 19th 07, 06:00 AM posted to alt.home.repair
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Posts: 1,393
Default Run versus Start Capacitors - How to tell

Tony Hwang writes:

There is no run or start specific caps. It depends where in the circuit.


You're mistaken. Please, nobody listen to that ignorance.
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  #12  
Old April 19th 07, 06:09 AM posted to alt.home.repair
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Default Run versus Start Capacitors - How to tell

Jeff Wisnia writes:

there really isn't any difference between a
"run" and a "start" capacitor, the term comes from the application, not
the design.


No, these are "different same" items.

Both are typically electrolytics which are compact but lossy. The start
type is rated for a low duty cycle so they can be made very compact and
very lossy (i.e., cheap). The run type must be physically bigger and more
expensive for the same capacitance to make it less lossy, so that it
doesn't overheat in a 100 percent duty cycle.

Weren't they past the phlogiston and ether theory when you studied EE?
Start vs run types vary in the real component of their impedance, which is
reflected in the resistive component of the lumped element model. This is
usually explained in dumbed-down terms of "ripple" for the non-engineer.
  #13  
Old April 19th 07, 06:57 AM posted to alt.home.repair
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Posts: 361
Default Run versus Start Capacitors - How to tell

dpb writes:

But it could be (and w/ a drill press it's what I'd expect) just a
capacitor-start motor to provide the starting torque.


I wouldn't expect to see a capacitor-start motor in a drill press.
Drill presses start up under no load (except some friction from the
bearings and belts) so they don't need much starting torque. A
capacitor-run motor provides a positive starting direction and better
running torque than a split-phase motor, without any need for a starting
switch or starting relay.

I have a Sears drill press with a capacitor-run motor. One bench
grinder is also capacitor-run.

Besides, starting capacitors are often in the range of hundreds of uF,
while run capacitors are usually tens of uF.

Dave
  #14  
Old April 20th 07, 03:27 PM posted to alt.home.repair
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Posts: 121
Default Run versus Start Capacitors - How to tell


"stoneattic" wrote in message
ups.com...
On Apr 18, 11:20 am, Tony Hwang wrote:
stoneattic wrote:
I have a 9" Craftsman (Sears) drill press that just smoked the motor
capacitor. I call Sears about a replacement and they want to sell me
the whole motor (of course). I'm trying to replace just the
capacitor but I don't know if it's a run or start. Here's what
labeled on the cap:


CBB60 SH
16mF +/- 5%
-25/70C
250VAC
50//60Hz
Wenling Star &Fire Capacitors Factory
E215152


The model of the drill is 137.219090 if that helps


How can I determine if it's a run or start cap?



No normal electric motor has a 16 MF start capacitor. And, most run
capacitors are 370 volt. You can replace it with a 16 MF 370 volt run
capacitor. They are available at W.W. Graingers or Johnstone. Or, why not
try Sears parts?

Al


  #15  
Old April 20th 07, 11:59 PM posted to alt.home.repair
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Posts: 1,303
Default Run versus Start Capacitors - How to tell

Richard J Kinch wrote:

Jeff Wisnia writes:


there really isn't any difference between a
"run" and a "start" capacitor, the term comes from the application, not
the design.



No, these are "different same" items.

Both are typically electrolytics which are compact but lossy. The start
type is rated for a low duty cycle so they can be made very compact and
very lossy (i.e., cheap). The run type must be physically bigger and more
expensive for the same capacitance to make it less lossy, so that it
doesn't overheat in a 100 percent duty cycle.

Weren't they past the phlogiston and ether theory when you studied EE?
Start vs run types vary in the real component of their impedance, which is
reflected in the resistive component of the lumped element model. This is
usually explained in dumbed-down terms of "ripple" for the non-engineer.



Hey Richard, I admitted yesterday that I screwed up by wording it that
way, but go ahead and beat on me if it feels good to you, I've got thick
skin. G

Peace,

Jeff

--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10^12 furlongs per fortnight.

  #16  
Old April 21st 07, 02:29 AM posted to alt.home.repair
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Posts: 165
Default Run versus Start Capacitors - How to tell

You may have trouble finding a generic 16mfd, but 15's are very common
and will work fine. You have a 10% +/- tolerance anyway. Larry

  #17  
Old May 22nd 07, 12:05 AM posted to alt.home.repair
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Posts: 1
Default Run versus Start Capacitors - How to tell

On Apr 18, 10:29 am, stoneattic wrote:
I have a 9" Craftsman (Sears) drill press that just smoked the motor
capacitor. I call Sears about a replacement and they want to sell me
the whole motor (of course). I'm trying to replace just the
capacitor but I don't know if it's a run or start. Here's what
labeled on the cap:

CBB60 SH
16mF +/- 5%
-25/70C
250VAC
50//60Hz
Wenling Star &Fire Capacitors Factory
E215152

The model of the drill is 137.219090 if that helps

How can I determine if it's a run or start cap?

thx


First, let me say that I am not an engineer, or electrician, or motor
repair person, but rather just a jack of all trades that plays with
things to figure them out so I cannot get technical for you here,
however, in the unlikely event that you still need this info, I have a
Craftsman 6 inch grinder that has the same capacitor and same
problem. I know that it is functioning as a starting capacitor since
I can give the wheel a spin by hand and turn it on and it will run all
day long, even after I have cut the capacitor totally out of the
system. Sears does sell them thru their parts section for 4.49 each
with a 6.99 shipping and handling charge plus any taxes for your area,
making the part cost 25% of a new grinder to me and the new ones have
a more powerful motor so I am also looking to find one cheaper
elsewhere.

Gary

  #18  
Old May 22nd 07, 06:28 AM posted to alt.home.repair
Dan
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Posts: 214
Default Run versus Start Capacitors - How to tell

\"mm" wrote in message
...
On Wed, 18 Apr 2007 11:05:18 -0400, Jeff Wisnia
wrote:

You'll be able to purchase a 16 mfd 250VAC motor capacitor at lots of
places. Getting one the correct size and shape will be the more
challenging part.


I guess a motor store would be better, but you could also check out
www.mouser.com and www.mcmelectronics.com I think I have the second
url right.

Jeff



I've used both Mouser & MCM for years for electronic items. Good sources.
Also I bet the 21ufd cap here would work:
http://www.action-electronics.com/capac.htm

This is the kind of thing that in most areas is easier to obtain through the
mail.

Dan


  #19  
Old May 22nd 07, 09:05 AM posted to alt.home.repair
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Posts: 254
Default Run versus Start Capacitors - How to tell

On Apr 19, 12:09 am, Richard J Kinch wrote:
Jeff Wisnia writes:
there really isn't any difference between a
"run" and a "start" capacitor, the term comes from the application, not
the design.


No, these are "different same" items.

Both are typically electrolytics which are compact but lossy. The start
type is rated for a low duty cycle so they can be made very compact and
very lossy (i.e., cheap). The run type must be physically bigger and more
expensive for the same capacitance to make it less lossy, so that it
doesn't overheat in a 100 percent duty cycle.

Weren't they past the phlogiston and ether theory when you studied EE?
Start vs run types vary in the real component of their impedance, which is
reflected in the resistive component of the lumped element model. This is
usually explained in dumbed-down terms of "ripple" for the non-engineer.


You sound like a hack. Lossy is an audio or compression term. Maybe
you are after...lousy?

  #20  
Old May 22nd 07, 05:13 PM posted to alt.home.repair
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Posts: 1,303
Default Run versus Start Capacitors - How to tell

wrote:

On Apr 19, 12:09 am, Richard J Kinch wrote:

Jeff Wisnia writes:

there really isn't any difference between a
"run" and a "start" capacitor, the term comes from the application, not
the design.


No, these are "different same" items.

Both are typically electrolytics which are compact but lossy. The start
type is rated for a low duty cycle so they can be made very compact and
very lossy (i.e., cheap). The run type must be physically bigger and more
expensive for the same capacitance to make it less lossy, so that it
doesn't overheat in a 100 percent duty cycle.

Weren't they past the phlogiston and ether theory when you studied EE?
Start vs run types vary in the real component of their impedance, which is
reflected in the resistive component of the lumped element model. This is
usually explained in dumbed-down terms of "ripple" for the non-engineer.



You sound like a hack. Lossy is an audio or compression term. Maybe
you are after...lousy?


No, I don't think Richard is a hack. He was right to pounce on me over
that mistake.

I stand corrected. I either never learned or never thought about the
operating requirement differences for "start" and "run" capacitors, but
it now seems obvious, especially since supply houses list them for one
or the other purpose.

Though, if push came to shove I'm sure one could use a run capacitor of
the correct capacitance rating to do a start capacitor's job, but not
the other way around, huh?

Jeff (Looking forward to attending his 50th MIT class reunion in less
than two weeks. G)

--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10^12 furlongs per fortnight.

 




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