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Explain pump motor start switch

Started by amdx July 17, 2014
Hi all,
  I helped my neighbor disassemble a pump motor, we had to remove the
centrifugal assembly from the shaft. The centrifugal assembly opens a 
switch when it gets up to speed. Opposite of what I thought would 
happen. The motor has a start capacitor.

I just did a Google search thinking I might just answer my own question,
but all I did was confirm what I thought I knew.

  So, why does the switch open when the motor gets up to speed?

What is the circuit before the switch closes vs. after the switch closes.

Yes, I'm sure the switch is closed at stall and is pushed open when the 
weight swings.
                                     Mikek

amdx wrote:
> > Hi all, > I helped my neighbor disassemble a pump motor, we had to remove the > centrifugal assembly from the shaft. The centrifugal assembly opens a > switch when it gets up to speed. Opposite of what I thought would > happen. The motor has a start capacitor. > > I just did a Google search thinking I might just answer my own question, > but all I did was confirm what I thought I knew. > > So, why does the switch open when the motor gets up to speed? > > What is the circuit before the switch closes vs. after the switch closes. > > Yes, I'm sure the switch is closed at stall and is pushed open when the > weight swings.
The start winding draws a lot of current, and is only needed to get the motor started. That start capacitor is a non-polar electrolytic. It can only take intermittent service without blowing the vent. The start capacitor causes a phase shift to the run winding, which provides the torque required to start the motor. At least it isn't using a potential relay. :) -- Anyone wanting to run for any political office in the US should have to have a DD214, and a honorable discharge.
On 17/07/14 20:59, amdx wrote:
> Hi all, > I helped my neighbor disassemble a pump motor, we had to remove the > centrifugal assembly from the shaft. The centrifugal assembly opens a > switch when it gets up to speed. Opposite of what I thought would > happen. The motor has a start capacitor. > > I just did a Google search thinking I might just answer my own question, > but all I did was confirm what I thought I knew. > > So, why does the switch open when the motor gets up to speed? > > What is the circuit before the switch closes vs. after the switch closes. > > Yes, I'm sure the switch is closed at stall and is pushed open when the > weight swings. > Mikek >
Why did you think the switch should close at speed ??
On 7/17/2014 8:22 AM, Rheilly Phoull wrote:
> On 17/07/14 20:59, amdx wrote: >> Hi all, >> I helped my neighbor disassemble a pump motor, we had to remove the >> centrifugal assembly from the shaft. The centrifugal assembly opens a >> switch when it gets up to speed. Opposite of what I thought would >> happen. The motor has a start capacitor. >> >> I just did a Google search thinking I might just answer my own question, >> but all I did was confirm what I thought I knew. >> >> So, why does the switch open when the motor gets up to speed? >> >> What is the circuit before the switch closes vs. after the switch closes. >> >> Yes, I'm sure the switch is closed at stall and is pushed open when the >> weight swings. >> Mikek >> > Why did you think the switch should close at speed ??
Never mind. I don't know how I got my logic mixed up. Thanks, Mikek --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com
On Thu, 17 Jul 2014 07:59:15 -0500, amdx <nojunk@knology.net> wrote:

>Hi all, > I helped my neighbor disassemble a pump motor, we had to remove the >centrifugal assembly from the shaft. The centrifugal assembly opens a >switch when it gets up to speed. Opposite of what I thought would >happen. The motor has a start capacitor. > >I just did a Google search thinking I might just answer my own question, >but all I did was confirm what I thought I knew. > > So, why does the switch open when the motor gets up to speed? > >What is the circuit before the switch closes vs. after the switch closes. > >Yes, I'm sure the switch is closed at stall and is pushed open when the >weight swings. > Mikek
That switch is for the start winding. The start winding should not be energized for more than a few seconds because it will overheat. Make sure the start switch goes back in the same location on shaft. Depending on how the switch is actuated the wrong location will either prevent the switch from opening or else the switch will always be closed. So if the motor just hums when it is powered up then the switch is open, and if the motor does start correctly make sure it doesn't get hot real fast, because that will mean the switch is always closed. Eric
In article <lq8hb5$mn2$1@dont-email.me>, nojunk@knology.net says...
> > Hi all, > I helped my neighbor disassemble a pump motor, we had to remove the > centrifugal assembly from the shaft. The centrifugal assembly opens a > switch when it gets up to speed. Opposite of what I thought would > happen. The motor has a start capacitor. > > I just did a Google search thinking I might just answer my own question, > but all I did was confirm what I thought I knew. > > So, why does the switch open when the motor gets up to speed?
Centrifugal force. The spring that is holding the contacts together will be pulled back via the linkage that gets forced to the outside of the spin. And also, you only want the cap in circuit on initial start. You can get add on switchings to hang on shafts to do these wonderful things. An electronic starter will monitor the current and when the initial current drops off, the electronic switch disconnects the starting cap. Those types of electronic switches normally use a reed switch with a couple of turns of wire around the read to sense current. The switch turns on a triac. Also, you may see a washer wrapped up in the turns to create a shaded pole to prevent the reed from chattering. Jamie
In article <doqfs911locb318hd4qctviflbdfh3ipnf@4ax.com>, 
etpm@whidbey.com says...
> > On Thu, 17 Jul 2014 07:59:15 -0500, amdx <nojunk@knology.net> wrote: > > >Hi all, > > I helped my neighbor disassemble a pump motor, we had to remove the > >centrifugal assembly from the shaft. The centrifugal assembly opens a > >switch when it gets up to speed. Opposite of what I thought would > >happen. The motor has a start capacitor. > > > >I just did a Google search thinking I might just answer my own question, > >but all I did was confirm what I thought I knew. > > > > So, why does the switch open when the motor gets up to speed? > > > >What is the circuit before the switch closes vs. after the switch closes. > > > >Yes, I'm sure the switch is closed at stall and is pushed open when the > >weight swings. > > Mikek > That switch is for the start winding. The start winding should not be > energized for more than a few seconds because it will overheat. Make > sure the start switch goes back in the same location on shaft. > Depending on how the switch is actuated the wrong location will either > prevent the switch from opening or else the switch will always be > closed. So if the motor just hums when it is powered up then the > switch is open, and if the motor does start correctly make sure it > doesn't get hot real fast, because that will mean the switch is always > closed. > Eric
Just a slightly off topic note, one can make a cheap rotary converting with a cap start/run motor. You simply start the motor and let it run and then use the starter winding as the third leg.. It does not work as well as using a 3 phase motor but it does work! :) Jamie
On Thu, 17 Jul 2014 18:51:23 -0400, "Maynard A. Philbrook Jr."
<jamie_ka1lpa@charter.net> wrote:

>In article <doqfs911locb318hd4qctviflbdfh3ipnf@4ax.com>, >etpm@whidbey.com says... >> >> On Thu, 17 Jul 2014 07:59:15 -0500, amdx <nojunk@knology.net> wrote: >> >> >Hi all, >> > I helped my neighbor disassemble a pump motor, we had to remove the >> >centrifugal assembly from the shaft. The centrifugal assembly opens a >> >switch when it gets up to speed. Opposite of what I thought would >> >happen. The motor has a start capacitor. >> > >> >I just did a Google search thinking I might just answer my own question, >> >but all I did was confirm what I thought I knew. >> > >> > So, why does the switch open when the motor gets up to speed? >> > >> >What is the circuit before the switch closes vs. after the switch closes. >> > >> >Yes, I'm sure the switch is closed at stall and is pushed open when the >> >weight swings. >> > Mikek >> That switch is for the start winding. The start winding should not be >> energized for more than a few seconds because it will overheat. Make >> sure the start switch goes back in the same location on shaft. >> Depending on how the switch is actuated the wrong location will either >> prevent the switch from opening or else the switch will always be >> closed. So if the motor just hums when it is powered up then the >> switch is open, and if the motor does start correctly make sure it >> doesn't get hot real fast, because that will mean the switch is always >> closed. >> Eric > >Just a slightly off topic note, one can make a cheap rotary converting >with a cap start/run motor. You simply start the motor and let it run >and then use the starter winding as the third leg.. > > It does not work as well as using a 3 phase motor but it does work! :) > >Jamie
How much current can you draw from this setup? I have made several rotary phase converters that were properly balanced and in fact my shop runs with one (that I bought before I understood well how to make one) that runs modern CNC equipment. I just can't see how it would be worth the trouble trying to get enough current...wait, I see now. You really only need the manufactured phase to get the three phase motor started. It will then draw enough current from the single phase line and won't really need the current from the third phase unless really loaded. Nevertheless, I wouldn't bother. With only a little more work and some oil filled caps from my box-o-caps I could whip up another with motors I have already. As an aside, it is interesting how a person can learn and understand a lot about a particular aspect of a certain subject, namely AC electricity and poly phase motors and generators, and yet understand practically nothing about the subject of AC electricity as a whole. Especially how radio waves propagate, reflect, and travel down wires to and from antennas, and how antennas themselves work. For me it's kinda like voodoo. Eric
On 7/17/2014 5:48 PM, Maynard A. Philbrook Jr. wrote:
> In article <lq8hb5$mn2$1@dont-email.me>, nojunk@knology.net says... >> >> Hi all, >> I helped my neighbor disassemble a pump motor, we had to remove the >> centrifugal assembly from the shaft. The centrifugal assembly opens a >> switch when it gets up to speed. Opposite of what I thought would >> happen. The motor has a start capacitor. >> >> I just did a Google search thinking I might just answer my own question, >> but all I did was confirm what I thought I knew. >> >> So, why does the switch open when the motor gets up to speed? >
I have already explained, I got my logic backwards. I understand how it works. Then my question was poorly ask. What I meant to sask, what is the function performed when the switch opens at speed? Ans. Stops current flow in the start winding. nuf said, Mikek I'm embarrassed, well, a little bit.
In article <lq9s7q$q7q$1@dont-email.me>, nojunk@knology.net says...
> > On 7/17/2014 5:48 PM, Maynard A. Philbrook Jr. wrote: > > In article <lq8hb5$mn2$1@dont-email.me>, nojunk@knology.net says... > >> > >> Hi all, > >> I helped my neighbor disassemble a pump motor, we had to remove the > >> centrifugal assembly from the shaft. The centrifugal assembly opens a > >> switch when it gets up to speed. Opposite of what I thought would > >> happen. The motor has a start capacitor. > >> > >> I just did a Google search thinking I might just answer my own question, > >> but all I did was confirm what I thought I knew. > >> > >> So, why does the switch open when the motor gets up to speed? > > > > I have already explained, I got my logic backwards. > I understand how it works. > Then my question was poorly ask. What I meant to sask, what is the > function performed when the switch opens at speed? Ans. Stops current > flow in the start winding. > > nuf said, Mikek > > I'm embarrassed, well, a little bit.
No, you're very red in the face! :) Jamie