Using Power Factor to Check Capacitors Under Load
ฝัง
- เผยแพร่เมื่อ 17 ก.ย. 2024
- The Supco Redfish iDVM550 Power Quality Meter includes a function with which it can measure real-time power factor on a load. In this video, Kaleb shows why using power factor to test capacitors under load is a valuable feature, and he shows how to use the Redfish iDVM550 to do it!
The power triangle of an inductive load contains three sides: reactive power on the side, real power on the bottom, and apparent power on the hypotenuse. Apparent power (volt-amps/VA) is a function of real power (true watts) and reactive power (VAr), and the power factor (theta or cos theta) is the angle between apparent power and real power. An inductive load generates a magnetic field, which will result in some reactive power that doesn't do any work.
As we get more reactive power, the gap between apparent power and real power increases. When that happens, the inductive load uses more utility power to work and becomes inefficient. Capacitors provide reactive power, thus decreasing the reactive power required from the utility and closing the gap between real and apparent power. The best power factor is unity or 1; anything less than that indicates that there is reactive power.
If you set the meter to kilowatts, the meter will display kilowatts, amps, and voltage to see the real power. You can also see the lag or lead, which indicates reactive power. Pressing "function" will show you the apparent power. Pressing "function" again will show you cos theta, which is your power factor. A power factor of unity (1) is ideal but not always realistic; a low power factor may indicate a weak capacitor.
When measuring the amperage, you want to make sure that the clamp is as far away from other wires as possible as not to pick up readings from nearby wires. The wire should also be at the center of the clip. Meanwhile, you use the meter leads to check the voltage (usually at the contactor or across the capacitor). You can use the measurements taken with the Supco Redfish iDVM550 and enter them into the Under Load Capacitor Test tool on the HVAC School app.
Alternatively, you could use the Supco TechLink app. The meter's readings link directly to the app, which allows you to see the power factor automatically.
Supco Redfish iDVM550 Power Quality Meter and resources: www.trutechtoo...
Read all the tech tips, take the quizzes, and find our handy calculators at www.hvacrschoo...
Thank you. I was just telling my husband this morning that I didn't know how to use all the functions of my redfish. Are yall Mind readers? Do you diagnose systems from your office chair too?
Idk about them but I always diagnose from the office 😂
a wonderful PF-cap video... also, the solar inverters and VFD motor drives can create 5th and 7th harmonics that can burnout equipment on the grid.... thanks... 🙂
great video!!!
This type of test is done during R&D of a motor to confirm engineers math and capacitor choice. In the field a normal clamp-on multi-meter using voltage and amps is all that is required. Amps X 2652 ÷ Volts = uF. This is under real world load for given conditions. Mr. Psychometrics correctly pointed this formula out. Have done it hundreds of times. No apps or fancy meters required. Your overcomplicating something for what reason, your forgetting K.I.S.S. principle, unless your trying to sell meters.
What is K . I.s.s?
@@dreadone6894 keep it simple stupid
@@dreadone6894 Keep It Simple " Stupid "
Please clarify something for me.
If the power factor is less than 0.94 and indicates a weak cap, what does a power factor of 1.5 indicate?
Great video!
do power factor really safe money am using 10 motor in wood work shop can power factor cut my bill
Another great video and explanation to
Question, does this meter have a low impedance selection/option.
I don't think it was mentioned, but doesn't the load play a roll? If you inadvertently use this testing method with say a compressor or fan that is unloaded (staged) won't that skew the results?
Yes it would. It would be important for any technician to make sure there is a load on the circuit before making any power factor measurement of value
@@kalebsaleeby3354 Not just a "load" but the correct or expected load.
FYI Gents....Bought this meter 2 years ago and loved it right up until the clamp broke 2 months ago... Called Redfish for service support and it turns out that outside of the 1 year warranty there is absolutely no service support for this tool..
At what power factor would you start to suspect the capacitors. Since the manufactures dont put out power factor specs wouldn't you need a baseline reading to be able to determine that there was a change?? And since the voltage is an integral element in the power factor computation would a change in voltage from your baseline reading cause a change in power factor?
JT H he mentioned anything below .94 would be something to look at as a possible problem. 1.0 is perfect.
@@JoeB3 don't know who told him it needs to be unity. Copeland has an application engineering sheet with this in it....It is always possible to correct a motor to unity power factor, but total correction is normally not recommended. The
influence of other reactive forces on the power line, such as changing motor or transformer load, is unpredictable,
and if the power factor is over-corrected, it can cause high currents, high magnetic side pull forces on the motor
rotor, high voltage, and transient motor over-torque much greater than full load motor torque. Whether
overcorrection will cause motor damage is uncertain, but there is evidence that motor life can be shortened by
voltage spikes caused by over-correction. A safer course is a more conservative one, limiting correction to the .9
(or 90%) level.... Ref AE9-1249
.94 and you're concerned? Come on man that's a bit egregious isn't it? Even Emerson says correcting to 90% .90 is more than acceptable..... Emerson AE9-1249 sec.8
I have an 04 condenser, my compressor's power factor is 0.75. The rated capacitor is 80MFD, and installed Cap is well in range , at 78MFD. I can only assume that the loss is due to compressor wear. Is that correct? I imputed my data into the calculations provided on The Engineering Mindset's video 'Power Factor Explained' and converted that to MFD and I got 92MFD. Would that increase due more harm than good to my compressor?
So I’ve reviewed passed podcasts again, and I’m seeing that you never recommended upsizing the capacitor, which is a rule I follow. So a better question would be why am I seeing a low power factor with the correct Cap, and is there any + tolerance that you would be comfortable with or know of (for the sake of restoring efficiency)? Thank you. I would also like to thank you for all of the great free training you provide. You have really helped me to grow in my career and have provided an easy platform to learn better practices, and to continually become a better technician.
@@simonwatson474you commented on a comment lol
This was two years ago but sounds like compression ratio was off or perhaps contamination to the refrigerant.
If you see this, did you ever get an answer?
What calculation?
I ate a power bar after this video.
Don’t you mean SYSTEM Power Factor vs Capacitor Power Factor? Please advise!
Hi can you do this with other meters
Ah yes 2552 × Amps ÷ Voltage = MuF
2650 * ?? X amps / Voltage = MuF
So if you have a known good cap and the measurement says otherwise is that an indicator that the inductive load may be in early failure?
That would likely be the case. PSC motors are designed for efficiency and high power factor a their operating load point. The run cap value is selected to form symmetrical rotating magnetic fields at that load point. If the fields become asymmetrical then the current in one or both windings will be higher than the mains current causing losses and heating. If the run cap isn't the element that has deviated from the design parameters then it seems that something else, a bearing going bad or such, has moved the load point and dropped the power factor.
@@jkbrown5496 Thank you. It seemed like simple arithmetic but I wanted to hear it.
InsideOfMyOwnMind may also mean that someone put the wrong capacitor as a replacement!
@@DougMarsh1983 Yeah, ones I've seen had the cap spec on the motor or on the plate
How does the app connect to the meter?
….wireless Bluetooth connectivity like everything else.