srinivasan
Member
- Location
- Bangalore,India
if power factor is above 0.95 voltage gain occur in the motor and due to voltage drop over heat is induced(sluggish) . is it a disadvantage and how?
power factor
- Thread starter srinivasan
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srinivasan
Member
- Location
- Bangalore,India
Benefit - Improve System Operating Characteristics (Gain Voltage):A good power factor (0.95) provides a "stiffer" voltage, typically a 1-2% voltage rise can be
expected when power factor is brought to +\-0.95. Excessive voltage drops can make your
motors sluggish, and cause them to overheat. Low voltage also interferes with lighting, the
proper application of motor controls and electrical and electronic instruments. Motor
performance is improved and so is production. this is the concept i studied from benefit of power factor improvement . is motor over heat make any problem to the load
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
This is all hogwash spewed out by the scam artists trying to sell power factor improvement as the magic cure to all of our problems. It's just not relevant. You have voltage drop as a result of having too small of conductors for a given load. Properly sizing the conductors is how you make that problem go away.
Improving power factor benefits the utility supplying the power, but not the end user, unless the utility penalizes the user for having poor power factor. Improving power factor avoids those penalties, that is the ONLY tangible benefit. If the utility does not penalize you, don't waste time and effort on it unless you just want to be a good citizen and spend money for the benefit of the fat cats who own your utility. I prefer to donate my excess money to more worthy charities.
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T.M.Haja Sahib
Guest
Your proposal for improving voltage by using capacitors is a sound one,provided the condition is favorable.To find out what that condition is you perform experiments in your electrical lab under the supervision of your Professor,using capacitors across a any load to see whether there is any improvement in voltage by increasing the capacitor size.If you can find out the necessary condition to observe any appreciable voltage rise due to capacitors,report it here.
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kwired
Electron manager
- Location
- NE Nebraska
The power factor at the motor does not change, the power factor ahead of the correction device does. The only thing gained is reduced losses in the branch circuit and feeders because of lowered current - this is usually rather small but can still be worth the savings. The main reason for power factor correction is to save on POCO penalties for bad power factor - if they charge these penalties.
srinivasan
Member
- Location
- Bangalore,India
Reactive Power produces no productive work. An inductive motor with power applied and noload on its shaft should draw almost nil productive power, since no output work is being
accomplished until a load is applied. The current associated with no-load motor readings is
almost entirely "Reactive" Power...... reactive power is used to generate the magnetic field in ac motor.... if all the motor start at a time the reactive power requirement is increased ..... if the reactive power increases the power factor will get decrease . by this concept motor does change the power factor.. please explain my concept is correct or not
srinivasan
Member
- Location
- Bangalore,India
my proposal is for improving the power factor but if the voltage rise make any problem . i got a answer by proper selection of conductor we can solve it. when the capacitor is connected across the load the power quality problem is eliminated including harmonics. if the size increases the lagging of reactive power is reduced so small amount of voltage will rise and will not be appreciable ... this is my assumption ...perform experiment in lab is little bit difficult
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
I see more equipment failures and misoperation due to the improper addition of PF correction capacitors than I do from the PF itself.
If you can not duplicate real world conditions in your lab, then I guarantee you will be producing useless outcomes.
kwired
Electron manager
- Location
- NE Nebraska
My explanation was about the fact that the amount of reactive power is the same in the motor. The power factor capacitor corrects this reactive power but only at the point in the circuit where it is connected as well as points ahead of it.
Also a motor with no load connected still consumes some power just to turn the rotor. The more mass there is to the rotor the more energy is needed to turn it. This can be included in the motors efficiency rating, the HP rating of the motor should be what is available at the output, what is input is going to be higher because no motor is 100% efficient.
srinivasan
Member
- Location
- Bangalore,India
i'm very eager do real world conditions in lab ... and also i did also my subject lab in well.... i have more interest but my authorities doesn't interest to teach out of subject ..... but i know practical is real world subject books are imagination to real world subject . that's why i came here... i won't be a useless outcome..
Agreed. The PFC results in lower supply currents. That can reduce distribution losses and/or reduced conductor sizes.
No load losses are I2R and iron losses on the stator side and windage and friction on the rotor side. Rotor inertia doesn't come into it much other than during the acceleration which might last a second or so.
kwired
Electron manager
- Location
- NE Nebraska
I can agree with that. Just turning the rotor doesn't consume energy, but losses like friction, windage and iron losses do. We do that with space satellites - put them in rotation and they only use the energy required to put them in rotation and then it is maintained until something external effects it - there is much less resistance to rotation in space - pretty much has to be impact with another object.
jumper
Senior Member
- Location
- 3 Hr 2 Min from Winged Horses
I believe OP is in a energy management course for industry.
http://www.pdhonline.org/courses/e144/e144content.pdf
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
Good observation, the wording is too exact to be coincidental, I think you are right, or at least someone has plagiarized something somewhere in this.
While I agree with most of what is said in that course, I think the issue of voltage rise is at best overblown as to importance and in some aspects just incorrect. For example I'm sick and tired of hat "conductor size" argument. Conductor sizing is based on code rules, not power factor correction, it's a spurious argument.
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T.M.Haja Sahib
Guest
No your answer is wrong .During normal load operation,you may overcome problems due to voltage rise due to addition of capacitors by 'proper'selection of conductor size.But during very light load operation,the voltage rise could become excessive.How are you going to solve it?You may find answer in the link at post#14!
Would sir care to give a worked example of proper conductor size selection can overcome voltage rise due to the addition of capacitors?
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T.M.Haja Sahib
Guest
What! You are not believing me?!
If you don't want or can't, that's fine. I'm not going to ask a hundred times.
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T.M.Haja Sahib
Guest
Okay I first try give a outline of principles involved.We have to agree first.
%voltage increase = KVAR of capacitor x% impedance of transformer
............................. KVA of Transformer
% impedance of transformer may be 2 to 9% and depending on the low lagging power factor of load, KVAR of capacitor may be equal to KVA of Transformer.So a voltage rise of 9% can exist.By selection of cable with suitable voltage drop/meter,the entire voltage increase of 9% may be dropped along the cable connecting the load so that rated voltage is available across the loads terminals.But if permissible voltage variation across loads terminal is 5%,it may be exceeded at very light load condition.
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