Is this a very poor description or am I ignorant?...

[RheillyPhoull]

On 18/07/2020 2:06 am, Ricketty C wrote:

On Friday, July 17, 2020 at 1:55:53 PM UTC-4, amdx wrote:
On 7/17/2020 12:39 PM, Ricketty C wrote:
On Friday, July 17, 2020 at 1:14:34 PM UTC-4, amdx wrote:
On 7/17/2020 11:48 AM, Ricketty C wrote:
On Friday, July 17, 2020 at 12:27:17 PM UTC-4, amdx wrote:
*What exactly is the Work of Start Capacitor?*

For single-phase motors normally have both the run and start capacitor.
However, they work differently. The start capacitor produces a bolt of
energy to the motor for it to run; while for run capacitor helps
maintain the functioning of the motor when the start capacitor switches
off. Start capacitor has the ability to store more charge than the run
capacitor.

Something else to observe with a start capacitor is getting burn out
since they work is to accumulate energy to speedily burst it out to
start the motor. How can you tell if the start capacitor is bad? You can
identify through two signs. First, when your motor is not starting after
you ignite it as usual, or if it takes longer than expected to respond.
It means the start capacitor is dead or almost to go bad completely.

https://understanding-air-compressors.com/compressor-capacitors/
 My explanation would be, the run capacitor causes a phase shift of the
current in the start winding, this in relationship to the main winding
cause an increase in torque to start the motor.

I think they are using more of a DC analogy, that I don\'t think applies.
I agree that the person who wrote this web page doesn\'t really understand the function of a start capacitor. Talking about \"accumulate energy to speedily burst it out to start the motor\" as you say might make sense in a DC circuit, but not in an AC circuit.

But for most people reading the page to fix their AC this is as much as they need. Bad start capacitor causes symptoms when starting the motor... good enough to replace a $5 part and move on.

This is from a different site,

Others have similar descriptions, It seem that\'s a common description in
the industry.

\'To do this HVAC units
https://en.wikipedia.org/wiki/HVAC_control_system> use what are called
Start and RUN capacitors.

# *A Start Capacitor* holds an extra charge to start a motor moving.
# *A Run Capacitor* keeps a motor running smoothly with no up and down
spikes.\'
I don\'t find those phrases in the above link.

Sorry, that link was in my quote. As I said \" Others have similar
descriptions\"

My quote was from here,

https://www.hvachowto.com/start-run-capacitor/

                                    Mikek



One of the nice things about Wikipedia is any significant factual statement is supposed to be supported by a reference. I\'d like to see the references for those statements.

The way they describe the start and run caps you would think the same part could do both jobs.

I\'m not a motor guy, but I don\'t recall a \"run\" capacitor. Reading your reference they talk about the two functions of capacitors, then talk about them being combined in one package.

\"A dual capacitor will most often have one side to start the compressor (Herm) and the other side to start the condensing fan motor. The third single leg on a dual capacitor is a shared common leg.\"

So which is it, one start and one run capacitor or start for two motors?

I think it is the latter. My (limited) understanding is that the start capacitor shifts the phase of the AC current for a motor winding that allows the motor to ramp up to speed and when a centrifugal switch removes the cap at higher RPM the winding just becomes part of the regular motor windings allowing the motor to run at highest efficiency.

As Larkin mentioned, on smaller motors where efficiency is often not so important a shading winding is used to permanently provide this starting torque resulting in some loss of effiency.

A run cap is very real in the larger horsepower motors, it adds to the
current when running and also there are fractional hp motors that use a
run cap, many air con units have such for the circulating fan.

 

[server]

On Sat, 18 Jul 2020 08:31:00 +0800, RheillyPhoull
<Rheilly@bigslong.com> wrote:

On 18/07/2020 2:06 am, Ricketty C wrote:
On Friday, July 17, 2020 at 1:55:53 PM UTC-4, amdx wrote:
On 7/17/2020 12:39 PM, Ricketty C wrote:
On Friday, July 17, 2020 at 1:14:34 PM UTC-4, amdx wrote:
On 7/17/2020 11:48 AM, Ricketty C wrote:
On Friday, July 17, 2020 at 12:27:17 PM UTC-4, amdx wrote:
*What exactly is the Work of Start Capacitor?*

For single-phase motors normally have both the run and start capacitor.
However, they work differently. The start capacitor produces a bolt of
energy to the motor for it to run; while for run capacitor helps
maintain the functioning of the motor when the start capacitor switches
off. Start capacitor has the ability to store more charge than the run
capacitor.

Something else to observe with a start capacitor is getting burn out
since they work is to accumulate energy to speedily burst it out to
start the motor. How can you tell if the start capacitor is bad? You can
identify through two signs. First, when your motor is not starting after
you ignite it as usual, or if it takes longer than expected to respond.
It means the start capacitor is dead or almost to go bad completely.

https://understanding-air-compressors.com/compressor-capacitors/
 My explanation would be, the run capacitor causes a phase shift of the
current in the start winding, this in relationship to the main winding
cause an increase in torque to start the motor.

I think they are using more of a DC analogy, that I don\'t think applies.
I agree that the person who wrote this web page doesn\'t really understand the function of a start capacitor. Talking about \"accumulate energy to speedily burst it out to start the motor\" as you say might make sense in a DC circuit, but not in an AC circuit.

But for most people reading the page to fix their AC this is as much as they need. Bad start capacitor causes symptoms when starting the motor... good enough to replace a $5 part and move on.

This is from a different site,

Others have similar descriptions, It seem that\'s a common description in
the industry.

\'To do this HVAC units
https://en.wikipedia.org/wiki/HVAC_control_system> use what are called
Start and RUN capacitors.

# *A Start Capacitor* holds an extra charge to start a motor moving.
# *A Run Capacitor* keeps a motor running smoothly with no up and down
spikes.\'
I don\'t find those phrases in the above link.

Sorry, that link was in my quote. As I said \" Others have similar
descriptions\"

My quote was from here,

https://www.hvachowto.com/start-run-capacitor/

                                    Mikek



One of the nice things about Wikipedia is any significant factual statement is supposed to be supported by a reference. I\'d like to see the references for those statements.

The way they describe the start and run caps you would think the same part could do both jobs.

I\'m not a motor guy, but I don\'t recall a \"run\" capacitor. Reading your reference they talk about the two functions of capacitors, then talk about them being combined in one package.

\"A dual capacitor will most often have one side to start the compressor (Herm) and the other side to start the condensing fan motor. The third single leg on a dual capacitor is a shared common leg.\"

So which is it, one start and one run capacitor or start for two motors?

I think it is the latter. My (limited) understanding is that the start capacitor shifts the phase of the AC current for a motor winding that allows the motor to ramp up to speed and when a centrifugal switch removes the cap at higher RPM the winding just becomes part of the regular motor windings allowing the motor to run at highest efficiency.

As Larkin mentioned, on smaller motors where efficiency is often not so important a shading winding is used to permanently provide this starting torque resulting in some loss of effiency.

A run cap is very real in the larger horsepower motors, it adds to the
current when running and also there are fractional hp motors that use a
run cap, many air con units have such for the circulating fan.

Run caps were common on high-quality tape recorders, because the
motors were synchronous, not induction. An induction motor needs slip
to generate torque, and slip is speed error.





--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

 

[server]

On Sat, 18 Jul 2020 08:31:00 +0800, RheillyPhoull
<Rheilly@bigslong.com> wrote:

On 18/07/2020 2:06 am, Ricketty C wrote:
On Friday, July 17, 2020 at 1:55:53 PM UTC-4, amdx wrote:
On 7/17/2020 12:39 PM, Ricketty C wrote:
On Friday, July 17, 2020 at 1:14:34 PM UTC-4, amdx wrote:
On 7/17/2020 11:48 AM, Ricketty C wrote:
On Friday, July 17, 2020 at 12:27:17 PM UTC-4, amdx wrote:
*What exactly is the Work of Start Capacitor?*

For single-phase motors normally have both the run and start capacitor.
However, they work differently. The start capacitor produces a bolt of
energy to the motor for it to run; while for run capacitor helps
maintain the functioning of the motor when the start capacitor switches
off. Start capacitor has the ability to store more charge than the run
capacitor.

Something else to observe with a start capacitor is getting burn out
since they work is to accumulate energy to speedily burst it out to
start the motor. How can you tell if the start capacitor is bad? You can
identify through two signs. First, when your motor is not starting after
you ignite it as usual, or if it takes longer than expected to respond.
It means the start capacitor is dead or almost to go bad completely.

https://understanding-air-compressors.com/compressor-capacitors/
 My explanation would be, the run capacitor causes a phase shift of the
current in the start winding, this in relationship to the main winding
cause an increase in torque to start the motor.

I think they are using more of a DC analogy, that I don\'t think applies.
I agree that the person who wrote this web page doesn\'t really understand the function of a start capacitor. Talking about \"accumulate energy to speedily burst it out to start the motor\" as you say might make sense in a DC circuit, but not in an AC circuit.

But for most people reading the page to fix their AC this is as much as they need. Bad start capacitor causes symptoms when starting the motor... good enough to replace a $5 part and move on.

This is from a different site,

Others have similar descriptions, It seem that\'s a common description in
the industry.

\'To do this HVAC units
https://en.wikipedia.org/wiki/HVAC_control_system> use what are called
Start and RUN capacitors.

# *A Start Capacitor* holds an extra charge to start a motor moving.
# *A Run Capacitor* keeps a motor running smoothly with no up and down
spikes.\'
I don\'t find those phrases in the above link.

Sorry, that link was in my quote. As I said \" Others have similar
descriptions\"

My quote was from here,

https://www.hvachowto.com/start-run-capacitor/

                                    Mikek



One of the nice things about Wikipedia is any significant factual statement is supposed to be supported by a reference. I\'d like to see the references for those statements.

The way they describe the start and run caps you would think the same part could do both jobs.

I\'m not a motor guy, but I don\'t recall a \"run\" capacitor. Reading your reference they talk about the two functions of capacitors, then talk about them being combined in one package.

\"A dual capacitor will most often have one side to start the compressor (Herm) and the other side to start the condensing fan motor. The third single leg on a dual capacitor is a shared common leg.\"

So which is it, one start and one run capacitor or start for two motors?

I think it is the latter. My (limited) understanding is that the start capacitor shifts the phase of the AC current for a motor winding that allows the motor to ramp up to speed and when a centrifugal switch removes the cap at higher RPM the winding just becomes part of the regular motor windings allowing the motor to run at highest efficiency.

As Larkin mentioned, on smaller motors where efficiency is often not so important a shading winding is used to permanently provide this starting torque resulting in some loss of effiency.

A run cap is very real in the larger horsepower motors, it adds to the
current when running and also there are fractional hp motors that use a
run cap, many air con units have such for the circulating fan.

Run caps were common on high-quality tape recorders, because the
motors were synchronous, not induction. An induction motor needs slip
to generate torque, and slip is speed error.





--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

 

[server]

On Sat, 18 Jul 2020 08:31:00 +0800, RheillyPhoull
<Rheilly@bigslong.com> wrote:

On 18/07/2020 2:06 am, Ricketty C wrote:
On Friday, July 17, 2020 at 1:55:53 PM UTC-4, amdx wrote:
On 7/17/2020 12:39 PM, Ricketty C wrote:
On Friday, July 17, 2020 at 1:14:34 PM UTC-4, amdx wrote:
On 7/17/2020 11:48 AM, Ricketty C wrote:
On Friday, July 17, 2020 at 12:27:17 PM UTC-4, amdx wrote:
*What exactly is the Work of Start Capacitor?*

For single-phase motors normally have both the run and start capacitor.
However, they work differently. The start capacitor produces a bolt of
energy to the motor for it to run; while for run capacitor helps
maintain the functioning of the motor when the start capacitor switches
off. Start capacitor has the ability to store more charge than the run
capacitor.

Something else to observe with a start capacitor is getting burn out
since they work is to accumulate energy to speedily burst it out to
start the motor. How can you tell if the start capacitor is bad? You can
identify through two signs. First, when your motor is not starting after
you ignite it as usual, or if it takes longer than expected to respond.
It means the start capacitor is dead or almost to go bad completely.

https://understanding-air-compressors.com/compressor-capacitors/
 My explanation would be, the run capacitor causes a phase shift of the
current in the start winding, this in relationship to the main winding
cause an increase in torque to start the motor.

I think they are using more of a DC analogy, that I don\'t think applies.
I agree that the person who wrote this web page doesn\'t really understand the function of a start capacitor. Talking about \"accumulate energy to speedily burst it out to start the motor\" as you say might make sense in a DC circuit, but not in an AC circuit.

But for most people reading the page to fix their AC this is as much as they need. Bad start capacitor causes symptoms when starting the motor... good enough to replace a $5 part and move on.

This is from a different site,

Others have similar descriptions, It seem that\'s a common description in
the industry.

\'To do this HVAC units
https://en.wikipedia.org/wiki/HVAC_control_system> use what are called
Start and RUN capacitors.

# *A Start Capacitor* holds an extra charge to start a motor moving.
# *A Run Capacitor* keeps a motor running smoothly with no up and down
spikes.\'
I don\'t find those phrases in the above link.

Sorry, that link was in my quote. As I said \" Others have similar
descriptions\"

My quote was from here,

https://www.hvachowto.com/start-run-capacitor/

                                    Mikek



One of the nice things about Wikipedia is any significant factual statement is supposed to be supported by a reference. I\'d like to see the references for those statements.

The way they describe the start and run caps you would think the same part could do both jobs.

I\'m not a motor guy, but I don\'t recall a \"run\" capacitor. Reading your reference they talk about the two functions of capacitors, then talk about them being combined in one package.

\"A dual capacitor will most often have one side to start the compressor (Herm) and the other side to start the condensing fan motor. The third single leg on a dual capacitor is a shared common leg.\"

So which is it, one start and one run capacitor or start for two motors?

I think it is the latter. My (limited) understanding is that the start capacitor shifts the phase of the AC current for a motor winding that allows the motor to ramp up to speed and when a centrifugal switch removes the cap at higher RPM the winding just becomes part of the regular motor windings allowing the motor to run at highest efficiency.

As Larkin mentioned, on smaller motors where efficiency is often not so important a shading winding is used to permanently provide this starting torque resulting in some loss of effiency.

A run cap is very real in the larger horsepower motors, it adds to the
current when running and also there are fractional hp motors that use a
run cap, many air con units have such for the circulating fan.

Run caps were common on high-quality tape recorders, because the
motors were synchronous, not induction. An induction motor needs slip
to generate torque, and slip is speed error.





--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

 

[server]

On Fri, 17 Jul 2020 11:27:08 -0500, amdx <amdx@knology.net> wrote:

*What exactly is the Work of Start Capacitor?*

For single-phase motors normally have both the run and start capacitor.
However, they work differently. The start capacitor produces a bolt of
energy to the motor for it to run; while for run capacitor helps
maintain the functioning of the motor when the start capacitor switches
off. Start capacitor has the ability to store more charge than the run
capacitor.

A pure single phase motor doesn\'t produce a rotating magnetic field.
When power is applied, it might just start vibrating in place. You can
then turn it manually and it will start rotating either CW or CCW,
depending on in which direction you push it. After it starts rotating
it will rotate in that direction until the power is cut.

This would be a bit hard, if you had to manually turn the motor once
the power is applied.

A three phase motor produces a rotating magnetic field and the motor
starts automatically in the same direction (unless two phase wires are
swapped).

In practice a single phase motor is actually a two phase motor, in
which the second phase is generated with a series capacitor (produces
up to 90 phase shift) producing a rotating magnetic field and the
motor starts in the same direction.

I have never heard of \"run\" capacitors. Are these connected between
phase and neutral, then it would just be used for correcting the power
factor, since the motor power factor can be quite bad when lightly
loaded. However, the capacitor should not be too big, since it could
overcompensate and cause problems to the network.

If it is between the hot end of the main winding and between the hot
end of the start winding then it will constantly feed the second phase
to the start winding. If you have installed some copper for the start
winding, so why not use it also for normal operation (with reduced
power)? But OTOH, why not make the secondary winding strong enough so
that it can be constantly fed by the larger start capacitor ?

 

[server]

On Fri, 17 Jul 2020 11:27:08 -0500, amdx <amdx@knology.net> wrote:

*What exactly is the Work of Start Capacitor?*

For single-phase motors normally have both the run and start capacitor.
However, they work differently. The start capacitor produces a bolt of
energy to the motor for it to run; while for run capacitor helps
maintain the functioning of the motor when the start capacitor switches
off. Start capacitor has the ability to store more charge than the run
capacitor.

A pure single phase motor doesn\'t produce a rotating magnetic field.
When power is applied, it might just start vibrating in place. You can
then turn it manually and it will start rotating either CW or CCW,
depending on in which direction you push it. After it starts rotating
it will rotate in that direction until the power is cut.

This would be a bit hard, if you had to manually turn the motor once
the power is applied.

A three phase motor produces a rotating magnetic field and the motor
starts automatically in the same direction (unless two phase wires are
swapped).

In practice a single phase motor is actually a two phase motor, in
which the second phase is generated with a series capacitor (produces
up to 90 phase shift) producing a rotating magnetic field and the
motor starts in the same direction.

I have never heard of \"run\" capacitors. Are these connected between
phase and neutral, then it would just be used for correcting the power
factor, since the motor power factor can be quite bad when lightly
loaded. However, the capacitor should not be too big, since it could
overcompensate and cause problems to the network.

If it is between the hot end of the main winding and between the hot
end of the start winding then it will constantly feed the second phase
to the start winding. If you have installed some copper for the start
winding, so why not use it also for normal operation (with reduced
power)? But OTOH, why not make the secondary winding strong enough so
that it can be constantly fed by the larger start capacitor ?