capacitor replacement - PhasePerfect converters

[David Zaret]

has anyone replaced the caps in their PP units with "stock" 40uF capacitors that they source from a place other than PhasePerfect? i'm seriously considering it, given that they are standard capacitors... and *significantly* cheaper than purchased through PP. anyone do this?

thanks,

-- dz

[Bill Dufour]

Just make sure the voltage is as high or higher. Easy enough if the terminals are the same type and sex or do they solder on?
Bill D

[Rod Sheridan]

As Bill said, check capacitance and voltage, then go ahead…. Tegards, Rod

[Paul F Franklin]

I'll add a word of caution from my EE days. Once you enter the realm of capacitors used in electronic applications, meaning other than AC caps used for motor starting, there are factors beyond capacitance and voltage that can be important, such as maximum ripple current and effective series resistance. These things are likely to be important in a high power switching power supply like the PP digital convertors. If the caps are marked with a manufacturer and part no, and you can source them from alternate suppliers, full speed ahead. If all you know is the capacitance and voltage ratings, more caution is advised.

[David Zaret]

i appreciate all of the feedback, and certainly fully understand what's been discussed. the caps in the PP are simple - they are 370V, 40uF +/-6% round capacitors. they are readily available. the only difference between "stock" caps with the same specs and the ones in the machine is the resistor soldered across the leads for bleed-off, and the screw terminals vs. spade terminals. i can certainly solder on a resistor, and somehow figure out how to "convert" the spades to accept the screws.

surpluscenter.com has literally the exact capacitors that ship from PP, for **$5** each. same brand, same specs. but, they were manufactured in 2012. best i can tell, caps have a shelf life (even if unused), so that's out. grainger has caps of the same spec for ~$13 each, but they are made in china, something i generally try to avoid (when possible). i would spend a little more for higher quality capacitors (if such a thing even exists), but PP wants $350 for 8 ($44 each). it seems quite hard to justify that cost when they are off-the-shelf items.

bottom line, i'm not yet sure what approach to take. i appreciate any and all guidance.

here are the surpluscenter.com caps: https://www.surpluscenter.com/Electrical/Capacitors/Motor-Run-Capacitors/40-MFD-370-Volt-AC-Run-Capacitor-CSC-325P406H37M36A4XSN-22-1338.axd

[Warren Lake]

only replaced caps once on one of two rotos and that had well over 30 years use on it. I read here before that electronic brakes will take out capacitors early. Only have one machine a radial with a Short Stop. It will be taken off because of what I read here. Not a big deal but I dont need electronic breaking on one machine when others dont have it.

[Halgeir Wold]

I've been in electronics my whole professional life, covering design, service an repair, - AOT...
If you buy your parts from reputable dealers, you should be OK... in the US you have Mouser, Digikey, Allied - and several more... for capacitors and semiconductors, I'd stay away from Ebay, - at least "oriental" vendors.... Even if some of them actually are OK and serious about their bussiness, there are still a lot and way too much of fakes around...
Pay attention to specs and tolerances, and for power electronics, make sure you get the same or better temp. range....

[Bill Dufour]

I would get the cheap old ones and reform them before use. Seems cheap enough to try.
Bill D

https://landandmaritimeapps.dla.mil/programs/MilSpec/ListDocs.aspx?BasicDoc=MIL-HDBK-1131

[Aaron Inami]

same brand, same specs. but, they were manufactured in 2012. best i can tell, caps have a shelf life (even if unused), so that's out.


The shelf-life of 10 years really has to do with electrolytic capacitors. For film caps, the shelf life is much longer (film caps are pretty much indestructible except for defects and extreme voltage/temperature). I cannot find any detail on what kind of cap that CSC capacitor is from the surplus site. If it's an electrolytic, I would avoid it as all costs, lol.

If you are okay with a 10,000 hour runtime at 85 degrees Celsius (that's 185 Farenheit), you can get away with some $12-20 caps. If the operating temperature is less and voltage is less than what's rated on the cap, the actual runtime can be 3-5 times longer. Take a look at this list:

https://www.mouser.com/c/passive-components/capacitors/motor-start-capacitors-motor-run-capacitors/?q=motor%20run%20capacitor%2040&capacitance=40%20uF&voltage%20rating%20ac=370%20VAC~~470%20VAC&instock=y&rp=passive-components%2Fcapacitors%2Fmotor-start-capacitors-motor-run-capacitors%7C~Voltage%20Rating%20AC

They are all film caps. Unless you are a production shop running 8 hours a day for 5-10 years, it is not likely you will need the 60,000 hours caps.

If PP is asking $44 each, they are probably 60,000 hour film caps (that is 60,000 hours of runtime at 85 degrees).

10,000 hours is 8 hours a day (including weekend) for 3-1/2 years.

[Aaron Inami]

Oh, one more thought. If you are considering getting one of those from Mouser, pay specific attention to the physical size. That list is all 40MFD 470V caps, but some are physically larger than others. You need to make sure you can fit/mount them in the existing space.

[David Zaret]

aaron -- the CSC caps you see on the surpluscenter site are indeed what came out of the phaseperfect unit - that's what they are selling. they are just marking them up, dramatically. thanks for the info on the film vs. electrolytic, this makes sense, and i guess i need to figure out what those CSC caps are... i'm going to replace them every year, so the x0,000 hour life is irrelevant.






The shelf-life of 10 years really has to do with electrolytic capacitors. For film caps, the shelf life is much longer (film caps are pretty much indestructible except for defects and extreme voltage/temperature). I cannot find any detail on what kind of cap that CSC capacitor is from the surplus site. If it's an electrolytic, I would avoid it as all costs, lol.

If you are okay with a 10,000 hour runtime at 85 degrees Celsius (that's 185 Farenheit), you can get away with some $12-20 caps. If the operating temperature is less and voltage is less than what's rated on the cap, the actual runtime can be 3-5 times longer. Take a look at this list:

https://www.mouser.com/c/passive-components/capacitors/motor-start-capacitors-motor-run-capacitors/?q=motor%20run%20capacitor%2040&capacitance=40%20uF&voltage%20rating%20ac=370%20VAC~~470%20VAC&instock=y&rp=passive-components%2Fcapacitors%2Fmotor-start-capacitors-motor-run-capacitors%7C~Voltage%20Rating%20AC

They are all film caps. Unless you are a production shop running 8 hours a day for 5-10 years, it is not likely you will need the 60,000 hours caps.

If PP is asking $44 each, they are probably 60,000 hour film caps (that is 60,000 hours of runtime at 85 degrees).

10,000 hours is 8 hours a day (including weekend) for 3-1/2 years.

[Aaron Inami]

If you are planning to replace every year, take a look at this one:

https://www.mouser.com/ProductDetail/KEMET/C870CF35400AA0J?qs=pqRVuuzkf6aMuJoMDcS4Ng%3D%3D

It's a Class B (10,000 hours at 420VAC or 3,000 hours at 470VAC). The size is 45mm x 98mm. It is exactly the same width as your CSC and only 3 mm longer. At $10.76 each, it's very affordable. Mouser has 275 in stock. Kemet is a very good manufacturer for industrial type capacitors.

[Bill Dufour]

Why replace yearly? Is this for aircraft or healthcare use?
Bill D

[David Zaret]

my PP is the heart of my shop. i have multiple CNC-controlled, 3ph machines that depend on it, and stress it. i do this professionally, and it's well worth the insurance factor to replace them and ensure the PP is healthy.

the last time i replaced the caps was august, 2020. over the past month or so, i've seen the PP shut off periodically when i start my shaper with an "over voltage" error. it's getting more frequent - today it shut off on me three times during an 8 hour session. the shaper has a very large motor, and the inductive breaking really stresses the caps. PhasePerfect tells me that the health of those capacitors is the main culprit in the symptoms i see, and i cannot be down.

aaron i'll check those out - thanks.

-- -dz

[Aaron Inami]

That link you provided to the CSC capacitor has a picture of the capacitor and label. If you zoom on the label, you will see "A COMBUSTIBLE FLUID" which leads me to believe these are electrolytic caps. Film caps are solid material and do not contain any fluid. The Electrolytic caps do contain a fluid that can leak over time and dry out from heat exposure. They can also boil from extreme heat/usage which causes the case of the capacitor to bulge out (you may have seen this sometime in your life). Also, on the CSC caps it states "70 C" which stands for 70 degrees Celsius. Not quite as good as the 85 degree standard on the Kemet. No idea what this actually means on the label, but I have to assume the max rated temperature.

[David Zaret]

aaron thanks for the education - this is great. i think for right now, given that i'm having issues, i'll buy a set from PP and get back up and running. then moving forward, i'll source the caps. the one you posted looks great, and mouser has a panasonic one that is backordered until august that also looks viable. next year i'll go that way. thanks.

-- dz

[Brice Rogers]

An electrolytic capacitor is a "polarized capacitor whose anode or positive plate is made of a metal that forms an insulating oxide layer through anodization." Polarized means they work with DC (direct current). AC (motor) capacitors are not polarized. They work with...well...AC (alternating current). It is not uncommon that AC (non-polarized) caps are oil filled. Probably to help dissipate heat and also act as an internal insulator. Many/most oils are flammable. So, contrary to what Aaron mentioned, the AC capacitors are not electrolytic. On old electrolytic capacitors (DC) that have been sitting for many years, some people slowly apply voltage to "re-form" them. That apparently re-establishes the oxide layer inside. But on an AC (motor) capacitor that isn't necessary IMHO. (BTW, I'm a degreed EE).

I don't think that a (new - old stock) 10 year old oil-filled AC capacitor is going to be a problem as long as it has been stored under normal conditions (ie. not in the Sahara desert).

30-40 years ago AC capacitors used to seem to last nearly forever. But most of the current caps come from China and seem to have much shorter life spans. About every 5 years or so I need to replace the AC capacitors on my whole house air conditioner and on my swimming pool pump. Often when they fail they will bulge on the ends. That is a great clue that it has failed. Last week I replaced my pool pump capacitor. I bought one locally and bought a spare on ebay (for about 1/2 price).

So, buy the surplus caps and you'll probably not have any problems. Also buy a set of spares. Change to connectors on your phase converter so that you can just drop in the new caps and quickly connect it.

[David Zaret]

brice, thanks for the education - this thread has been very informative. i'm worried about the age of those surplus caps. i think that when the time comes, i'll spend a bit more for "newer" caps, and modify the wires as you suggested. Mouser sells panasonic caps of the same/better specs and size, and they are still certainly affordable enough to not be a consideration.

--- dz

[jim mills]

I was told by the PP people that the unit can be damaged if a cap goes out during use. I replaced mine at the 9 year mark. They told me most units sent in for repair after the 10 year mark are due to failed cap's. The repair can be in the $1,000's.

[David Zaret]

I was told by the PP people that the unit can be damaged if a cap goes out during use. I replaced mine at the 9 year mark. They told me most units sent in for repair after the 10 year mark are due to failed cap's. The repair can be in the $1,000's.

yep, i got the same info. i run my PP every day, sometimes 8+ hours a day... so my intent is to replace them yearly. just trying to come up with a more affordable approach, given that the caps are "standard."