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power factor - round 2
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philkryder at gmail
Mar 20, 2013, 11:57:05 PM3/20/13
to
A couple years back some folks in this group helped me to use a KillaWatt device to deterimine powerfactor on some "lighly loaded" ac motors.
Time has passed.
I installed corrective capacitance based on my spreadsheed and formulas provided by others in the group. Thanks for all the help.
More Time passed.
What we learned recently is that though the AVERAGE powerfactor is "low" - .5 or less sometimes,
there are SPECIAL PEAK LOAD EVENTS that may last for a few seconds (less than 5) every minute or two.
Coincident with those peak load events, control circuits in the same "neighborhood" - i.e. cicuit need to fire control solenoids for hydraulic controls. The motor is a half-horse 120v 60 cycle that drives a hydraulic pump. On average - 95% of the time - there is no load - but, when there is a a solenoid opens a valve to a hydralic motor and then, other solenoids open valves to hydraulic cylinders...
You can guess where this is going.
When the load is applied voltage drops from 120 nominal to 106 or so. Solenoids fail to fire. Power factor changes dramatically.
So, given that my KillaWatt only does averages, we rented a Fluke meter that records mins and maxes within each one-minute interval.
I'm inclined to re-tune the capacitors based on highest power Factor seen over an entire 10 hour shift, rather than the average seen by the Killawatt while I happen to be looking.
Any other suggested actions?
Also, "what happens" with a corrected circuit at a 98% power factor when the load increases and the motor's power factor rises from .5 to .85 causing the circuit to be "over corrected"
thanks in advance.
Phil
Time has passed.
I installed corrective capacitance based on my spreadsheed and formulas provided by others in the group. Thanks for all the help.
More Time passed.
What we learned recently is that though the AVERAGE powerfactor is "low" - .5 or less sometimes,
there are SPECIAL PEAK LOAD EVENTS that may last for a few seconds (less than 5) every minute or two.
Coincident with those peak load events, control circuits in the same "neighborhood" - i.e. cicuit need to fire control solenoids for hydraulic controls. The motor is a half-horse 120v 60 cycle that drives a hydraulic pump. On average - 95% of the time - there is no load - but, when there is a a solenoid opens a valve to a hydralic motor and then, other solenoids open valves to hydraulic cylinders...
You can guess where this is going.
When the load is applied voltage drops from 120 nominal to 106 or so. Solenoids fail to fire. Power factor changes dramatically.
So, given that my KillaWatt only does averages, we rented a Fluke meter that records mins and maxes within each one-minute interval.
I'm inclined to re-tune the capacitors based on highest power Factor seen over an entire 10 hour shift, rather than the average seen by the Killawatt while I happen to be looking.
Any other suggested actions?
Also, "what happens" with a corrected circuit at a 98% power factor when the load increases and the motor's power factor rises from .5 to .85 causing the circuit to be "over corrected"
thanks in advance.
Phil
g
Mar 21, 2013, 12:12:45 PM3/21/13
to
On 20/03/2013 20:57, philkryder at gmail wrote:
>
> What we learned recently is that though the AVERAGE powerfactor is "low" - .5 or less sometimes,
lots of inductive loads, 0.5 _is_ rather lousy
>
> What we learned recently is that though the AVERAGE powerfactor is "low" - .5 or less sometimes,
> there are SPECIAL PEAK LOAD EVENTS that may last for a few seconds (less than 5) every minute or two.
>
>
> Coincident with those peak load events, control circuits in the same "neighborhood" - i.e. cicuit need to fire
control solenoids for hydraulic controls. The motor is a half-horse
120v 60 cycle that drives a hydraulic pump.
On average - 95% of the time - there is no load - but, when there is a a
solenoid opens a valve to a hydralic motor
and then, other solenoids open valves to hydraulic cylinders...
>
> You can guess where this is going.
>
>
> When the load is applied voltage drops from 120 nominal to 106 or so. Solenoids fail to fire.
Provide more information re how long the voltage stays low.
>
> Coincident with those peak load events, control circuits in the same "neighborhood" - i.e. cicuit need to fire
control solenoids for hydraulic controls. The motor is a half-horse
120v 60 cycle that drives a hydraulic pump.
On average - 95% of the time - there is no load - but, when there is a a
solenoid opens a valve to a hydralic motor
and then, other solenoids open valves to hydraulic cylinders...
>
> You can guess where this is going.
>
>
> When the load is applied voltage drops from 120 nominal to 106 or so. Solenoids fail to fire.
If the voltage drops that much to a constant low 106 volts, then the
supply to the motor is dangerously under-dimensioned. Update the supply
to a larger cable and fuse. If you are talking about a short time
interval (less than 1 seconds) for the voltage drop then that is normal
due to the momentary high start current of the motor. The voltage should
come up to close to nominal after the motor runs at rated speed. But
since you are stating that the solenoids fail to fire, it indicates that
the voltage is too low over the time the motor runs...
//g
mike
Mar 21, 2013, 1:41:11 PM3/21/13
to
When you get the power bill, are you billed for volt-amps or watts?
If it ain't broke, don't fix it.
The KillAwatt is limited to 2kw or so. Anything that can be measured
with that
is IRRELEVANT.
When there's no load, the power factor is IRRELEVANT.
If you are billed for volt-amps or you just want to be a "good citizen",
You want to provide power factor correction at EACH point of load under
normal conditions for that load.
Judging from your statements, your problem is RESISTANCE in the wiring
or motors severely overloaded...or both.
Don't think it makes a lot of sense to try to power correct a transient
load at turn-on unless you switch it in ONLY during turn-on.
A 120V solenoid shouldn't fail to energize at 106V. I expect your
transient goes much lower than that.
You need a storage oscilloscope and a current/voltage probe to determine the
transient conditions that you experience.
Think the end result will be bigger wiring.
Jim Wilkins
Mar 21, 2013, 4:20:25 PM3/21/13
to
"philkryder at gmail" <philk...@gmail.com> wrote in message
news:84e05d07-831d-4eec...@googlegroups.com...
> Phil
http://www.nationalgridus.com/niagaramohawk/non_html/eff_elec-demand.pdf
jsw
news:84e05d07-831d-4eec...@googlegroups.com...
>What we learned recently is that though the AVERAGE
>powerfactor is "low" - .5 or less sometimes,
>there are SPECIAL PEAK LOAD EVENTS that may
>last for a few seconds (less than 5) every minute or two.
>...
>powerfactor is "low" - .5 or less sometimes,
>there are SPECIAL PEAK LOAD EVENTS that may
>last for a few seconds (less than 5) every minute or two.
> Phil
http://www.nationalgridus.com/niagaramohawk/non_html/eff_elec-demand.pdf
jsw
j
Mar 21, 2013, 6:25:43 PM3/21/13
to
On 3/20/2013 11:57 PM, philkryder at gmail wrote:
Overcompensating will lead to current leading voltage, and when your
motor loads that is what will happen. I don't see this as bringing any
happiness to the assorted solenoids et all.
You have a small motor, power factor correction at idle has no real
benefit as the savings are minor. If you really want a better PF for
some altruistic reason, then you will need to switch out the
compensation when demand goes up.
My recommendation is to just remove the capacitors.
Overcompensating will lead to current leading voltage, and when your
motor loads that is what will happen. I don't see this as bringing any
happiness to the assorted solenoids et all.
You have a small motor, power factor correction at idle has no real
benefit as the savings are minor. If you really want a better PF for
some altruistic reason, then you will need to switch out the
compensation when demand goes up.
My recommendation is to just remove the capacitors.
hub...@ccanoemail.com
Mar 21, 2013, 6:34:45 PM3/21/13
to
On Wed, 20 Mar 2013 20:57:05 -0700 (PDT), philkryder at gmail
<philk...@gmail.com> wrote:
> A couple years back some folks in this group helped me to use a KillaWatt device
> to deterimine powerfactor on some "lighly loaded" ac motors.
>Time has passed.
> I installed corrective capacitance based on my spreadsheed and formulas
>provided by others in the group. Thanks for all the help.
>More Time passed.
>What we learned recently is that though the AVERAGE powerfactor is "low" - .5 or less sometimes,
>there are SPECIAL PEAK LOAD EVENTS that may last for a few seconds (less than 5) every minute or two.
>Coincident with those peak load events, control circuits in the same "neighborhood" -
> i.e. circuit need to fire control solenoids for hydraulic controls.
<philk...@gmail.com> wrote:
> A couple years back some folks in this group helped me to use a KillaWatt device
> to deterimine powerfactor on some "lighly loaded" ac motors.
>Time has passed.
> I installed corrective capacitance based on my spreadsheed and formulas
>provided by others in the group. Thanks for all the help.
>More Time passed.
>What we learned recently is that though the AVERAGE powerfactor is "low" - .5 or less sometimes,
>there are SPECIAL PEAK LOAD EVENTS that may last for a few seconds (less than 5) every minute or two.
>Coincident with those peak load events, control circuits in the same "neighborhood" -
>The motor is a half-horse 120v 60 cycle that drives a hydraulic pump.
> On average - 95% of the time - there is no load - but, when there is a a solenoid opens
> a valve to a hydralic motor and then, other solenoids open valves to hydraulic cylinders...
>You can guess where this is going.
>When the load is applied voltage drops from 120 nominal to 106 or so. Solenoids fail to fire.
>Power factor changes dramatically.
>So, given that my KillaWatt only does averages, we rented a Fluke meter that records mins and maxes
> within each one-minute interval.
>I'm inclined to re-tune the capacitors based on highest power Factor seen over an entire 10 hour shift,
>rather than the average seen by the Killawatt while I happen to be looking.
>Any other suggested actions?
>Also, "what happens" with a corrected circuit at a 98% power factor when the load increases
> and the motor's power factor rises from .5 to .85 causing the circuit to be "over corrected"
>thanks in advance.
>Phil
It seems that we're talking about fairly small ac motors (?)
> On average - 95% of the time - there is no load - but, when there is a a solenoid opens
> a valve to a hydralic motor and then, other solenoids open valves to hydraulic cylinders...
>You can guess where this is going.
>When the load is applied voltage drops from 120 nominal to 106 or so. Solenoids fail to fire.
>Power factor changes dramatically.
>So, given that my KillaWatt only does averages, we rented a Fluke meter that records mins and maxes
> within each one-minute interval.
>I'm inclined to re-tune the capacitors based on highest power Factor seen over an entire 10 hour shift,
>rather than the average seen by the Killawatt while I happen to be looking.
>Any other suggested actions?
>Also, "what happens" with a corrected circuit at a 98% power factor when the load increases
> and the motor's power factor rises from .5 to .85 causing the circuit to be "over corrected"
>thanks in advance.
>Phil
hence small-ish capacitors (?) which might have a significant
recovery time (?)
Are the solenoids trying to pick-up before the capacitors have
recharged ?
.. just a thought.
Is there any way to time-delay the solenoids ?
... even for a test .. ?
... dunno.
John T.
--- news://freenews.netfront.net/ - complaints: ne...@netfront.net ---
philk...@gmail.com
Mar 21, 2013, 8:22:57 PM3/21/13
to
we are off grid.
We're not trying to save money.
We're trying to run more reliably.
Our initial problem was popped breakers due to the high current flow due to the imaginary current.
thus the power factor correction.
step 1 was to remove the caps. - done.
I still have the question "what happens when the caps are in place and the motor's power factor improves to .85 from the average .5?
j
Mar 22, 2013, 4:16:53 PM3/22/13
to
whether with the caps and the loaded motor whether it had become
capacitive. I think it may have, particularly if you had compensated to
a PF of 1.
You have a complex system,if you were on grid the grid would absorb the
resulting voltage spike. But your inverter has to deal with that and
what it does is unknown. Have you considered a DC pump?
Jim Wilkins
Mar 22, 2013, 4:45:50 PM3/22/13
to
"j" <mun...@att.net> wrote in message
news:kiie7e$rid$1...@news.albasani.net...
Or an accumulator?
http://www.engineersedge.com/hydraulic/accumulator_equations.htm
news:kiie7e$rid$1...@news.albasani.net...
http://www.engineersedge.com/hydraulic/accumulator_equations.htm
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