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dana198
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- I recently purchased a capacitor for my air compressor but the terminals are not marked by any means , i have never seen that before can anyone tell me what i should do ? Does it matter ?
AZFIREBALL said:The marking of capacitor terminals is an antiquated practice that is no longer necessary.
Is this whole post supposed to be a joke?AZFIREBALL said:The marking of capacitor terminals is an antiquated practice that is no longer necessary.
Capacitor terminals at various times in the past were designated with terms such as: In and Out, Up and Down, Plus and Minus, + and -, Charge and Discharge, etc. These terms where ambiguous to the neophyte to say the least.
As you know, today’s electric bolts consist mainly of poles and holes and are much more sophisticated than they once were. They therefore, are able to decipher which terminal is which, without the need for overt designations. And due to the fact the frequency of DC is much lower today than it once was; along with today’s environmental need to always be politically correct, the terminals must be capable of being used without prejudices or discrimination.
Then again, I might be wrong.
Probably. Maybe written with excessive Christmas lubrication.phinds said:Is this whole post supposed to be a joke?
If a joke it is in the same classification as the "inject chlorox for COVID" variety. Hopefully fueled by lubrication and not dementia.phinds said:Is this whole post supposed to be a joke?
This is completely and totally incorrect. Many modern capacitors are polarized and failure to recognize this can be disastrous.AZFIREBALL said:The marking of capacitor terminals is an antiquated practice that is no longer necessary.
A motor START capacitor will be rated at close to the motor voltage. A motor RUN capacitor needs to be rated for about 1.8 times the motor voltage.jrmichler said:Your capacitor is clearly marked 250 VAC. That is the correct rating for a capacitor intended for use in a 120 volt AC application, such as a motor start or motor run capacitor.
Why wouldn't that be the other way around?Baluncore said:A motor START capacitor will be rated at close to the motor voltage. A motor RUN capacitor needs to be rated for about 1.8 times the motor voltage.
Sorry for the injudiciousness. Too much Christmas Eggnog!jrmichler said:To the OP: Your capacitor is clearly marked 250 VAC. That is the correct rating for a capacitor intended for use in a 120 volt AC application, such as a motor start or motor run capacitor. Posts #2 and #4 are correct.
To everybody who wants to be helpful: This thread is about motor capacitors. It is not a general thread on electrolytic capacitors. Please stay on topic. Also realize that the OP is clearly not an electrical engineer, so this is not an appropriate thread for EE jokes such as Post #3.
Maybe you can explain why you think I put it backwards.sysprog said:Why wouldn't that be the other way around?
That makes sense to me ##-## I was thinking of initial current draw being greater on start ##-##Baluncore said:Maybe you can explain why you think I put it backwards.
The quick way to identify a run cap is from the higher voltage rating. I believe it is because with varying loads, the run capacitor can react with the winding inductance to generate higher voltages in the series circuit.
Yes, it has been deprecated...phinds said:Is this whole post supposed to be a joke?
You should have included the [ humor ] [ /humor ] tags...AZFIREBALL said:Sorry for the injudiciousness. Too much Christmas Eggnog!
Tell us about your multimeter. I assume it has a capacitance measuring function? How much difference? What kind of capacitor?CityguyUSA said:I know the theme here has been going back and forth from lighthearted comedy to some truth. For now I'd like to focus on the truth.
I have an A/C capacitor that has no markings regarding poles and that makes sense to me. What doesn't make sense is when I reverse my multimeter test leads and get a different capacitance result.
I did notice a very light coating of oil on the exterior so I'm going to replace it although I don't see any evidence of protrusion or obvious leaking locations but am I right about getting the same result regardless of which lead is on which pole?
So it needs replaced but is this the right one for 115v/230v currrently wired for 115v?Baluncore said:Maybe your AC capacitor is effectively built out of two DC capacitors in series. One has aged faster than the other, or become leaky, so the total capacitance has become asymmetric.
When a functional electrolytic capacitor is biased with DC, it "learns" to become a better capacitor. One of the two series capacitors becoming leaky, would explain the asymmetry.
50μF is about the right value for a "motor start capacitor" on a single phase 1 HP motor. I guess your motor has a centrifugal switch that disconnects the start cap once running. Some motors also have a run capacitor.CityguyUSA said:So it needs replaced but is this the right one for 115v/230v currrently wired for 115v?
I have one more interesting tidbit of orienting axial foil capacitors. The outer electrode is marked. Not directly relevant here: more a high end tube amp issue.CityguyUSA said:I know the theme here has been going back and forth from lighthearted comedy to some truth. For now I'd like to focus on the truth.
I have 2 capacitors. I assumed this was the run capacitor because it was dogging while cutting but it seems to start ok. The other capacitor is 340-408 mfd 115v.Baluncore said:50μF is about the right value for a "motor start capacitor" on a single phase 1 HP motor. I guess your motor has a centrifugal switch that disconnects the start cap once running. Some motors also have a run capacitor.
Replace it with a 50μF, 230 VAC capacitor if you can find one. Otherwise, a lower voltage rating would also be OK for 115 VAC.
You are probably right, the big one is the starter. The higher voltage is usually a run capacitor.CityguyUSA said:I have 2 capacitors. I assumed this was the run capacitor because it was dogging while cutting but it seems to start ok. The other capacitor is 340-408 mfd 115v.
ThanksBaluncore said:You are probably right, the big one is the starter. The higher voltage is usually a run capacitor.
Replace the faulty capacitor.
If that does not fix it, trace out the wiring diagram, including the motor windings and centrifugal switch. Then we can analyse the problem more deeply.
There could be several reasons why your capacitor terminals are not marked. One possibility is that the markings were accidentally removed or faded over time. Another possibility is that the capacitor is a non-polarized type, meaning it does not have designated positive and negative terminals. Lastly, some capacitors may have markings that are difficult to see, so you may need to look closely or use a magnifying glass to locate them.
If your capacitor is polarized, the positive terminal is typically marked with a plus sign (+) or a longer terminal lead. The negative terminal may be marked with a minus sign (-) or a shorter terminal lead. If there are no markings, you can use a multimeter to test the terminals and determine which one has a higher voltage reading, which would be the positive terminal.
If your capacitor is non-polarized, it does not matter which terminal you connect to positive or negative. However, if your capacitor is polarized and the markings are not visible, it is not recommended to use the capacitor as it may cause damage to your circuit or equipment. It is best to replace the capacitor with a properly marked one.
If your capacitor is polarized and you are unsure of the terminal markings, there is a risk of damaging your circuit or equipment if you connect it incorrectly. It is important to properly identify the terminals before use. Additionally, always make sure to discharge the capacitor before handling it to avoid any electrical shock.
To prevent the markings on your capacitor from fading, avoid exposing it to extreme temperatures or direct sunlight. You can also use a clear nail polish to seal the markings and protect them from rubbing off. Additionally, handle the capacitor with care to avoid accidentally rubbing off the markings.