Rpc simple design unbalanced

[rgray]

I had an rpc in the past that was so quiet that I had to remember to shut it down. I now have a 3 hp phoenix phase converter and it is very loud. Is it just poor quality? should I add caps to the run circuit? I actualy don't think it has a seperate start and run circuit.
Have you had any dealings with these? Did they just compromise on capacitors using start caps full time?
It has no contactor or relays.

 

[Ulma Doctor]

I had an rpc in the past that was so quiet that I had to remember to shut it down. I now have a 3 hp phoenix phase converter and it is very loud. Is it just poor quality?
No, it's not poor quality. the converter is just not balanced
should I add caps to the run circuit? I actualy don't think it has a seperate start and run circuit.
Correct, In 3 phase motors the circuits are not separate. it is the same circuit!
Have you had any dealings with these? Did they just compromise on capacitors using start caps full time?
​I have not actually worked with that brand, but you can think of it as a 3 phase motor starting device.
The capacitor is used to start the idler motor and drops out of circuit after the motor has started. no other capacitors are used it appears in this design. this is an unbalanced converter design.
if you were to leave a start capacitor in circuit like you would a run capacitor it would quickly overheat and fail.
start caps are not equipped to dissipate heat like a run capacitor. run capacitors are usually oil filled and can dissipate heat a lot easier and can stay in circuit constantly.
View attachment 58880

We add run capacitors between all 3 phases. as a result the generated legs power increases in proportion to the value of the added capacitors. different capacitor values are used for different size motors and balancing requirements.
Capacitors are not one size fits all, simple calculations can be made after the loaded voltage difference between legs has been established.
Ideally all 3 legs would equal in a perfect world, but we don't live there so we strive for 10% difference between legs to be considered balanced. i personally try to be closer to 5% difference and have achieved 2% for sensitive customer units.

if there are other questions, please don't hesitate to ask. i'm happy to help out.
mike)

 

[randyjaco]

I have a 5hp Phoenix RPC that runs very quiet. You might want to check with Phoenix

Randy

 

[Ulma Doctor]

I have a 5hp Phoenix RPC that runs very quiet. You might want to check with Phoenix

Randy

I would never buy a converter from anyone, when i can build a superior balanced converter myself and way cheaper.

 

[Uglydog]

Ulma Doc,
As soon as schools out this spring I'm hoping to actually balance my RPC, instead of merely changing the leads around like I did last summer. Changing the leads actually seems to improve performance, as I'm no longer blowing thermals on my 20hp 3phase lathe. But, following the direction of another thread on HM, I'd like to add a third leg thermal on all my 3phase old iron and balance the RPC.

Sounds like the place to start is with the assessment of amperage output on all legs coming out of the RPC using a clamp ampmeter. Does a 3phase machine need to be tuurned on in order to get an accurate reading? Does it matter which machine?

How do I best know where which capacitor to add, where to put it and how to connect it? If I can do this myself I believe I'd learn great heaps of stuff However, I don't want to trouble all of you with questions for which answers are obvious to all except us noobs.

Daryl
MN

Sure Phil, i can help out!!
i have seen the balance difference between legs to be 50 volts +/- the other 2 legs or a 20% difference if you want to look at it like that.
A RPC to be considered electrically balanced has only 10% difference between legs.
i have been able to realize less than 2% for sensitive units.

Balance is important for a few reasons:
an unbalanced RPC will run hotter than balanced unit
an unbalanced RPC will run louder than a balanced unit
an unbalanced RPC will consume more energy than a balanced unit
an unbalanced RPC will have a shortened life expectancy of a balanced unit.

Phil, if you can send a PM or post a picture of you RPC i'll be happy to advise you as to how to proceed.
i'm just going to need some information from you to start.
I'm happy to help out..
mike)

 

[Ulma Doctor]

Sounds like the place to start is with the assessment of amperage output on all legs coming out of the RPC using a clamp ampmeter. Does a 3phase machine need to be tuurned on in order to get an accurate reading? Does it matter which machine?

Hi Daryl,
I would place a typical load on the machines you would intend to use on the RPC for the most accurate balancing.

if you intend on using multiple machines at the same time, make sure that you start them one at a time.

do I best know where which capacitor to add, where to put it and how to connect it? If I can do this myself I believe I'd learn great heaps of stuff However, I don't want to trouble all of you with questions for which answers are obvious to all except us noobs.

Daryl,
i'm always happy to lend a hand wherever i can, you would not be bothering me in the least by asking questions.
​when you are ready to start tackling the balancing procedure, drop me a line i'll be glad to assist you

 

[Uglydog]

Thank you.
Come May please expect long and tedious interrogatory.
Would this be best as a forum item or as a series of PMs?
Will my endless questions be helpful to others?

Daryl
MN

Sounds like the place to start is with the assessment of amperage output on all legs coming out of the RPC using a clamp ampmeter. Does a 3phase machine need to be tuurned on in order to get an accurate reading? Does it matter which machine?

Hi Daryl,
I would place a typical load on the machines you would intend to use on the RPC for the most accurate balancing.

if you intend on using multiple machines at the same time, make sure that you start them one at a time.

do I best know where which capacitor to add, where to put it and how to connect it? If I can do this myself I believe I'd learn great heaps of stuff However, I don't want to trouble all of you with questions for which answers are obvious to all except us noobs.

Daryl,
i'm always happy to lend a hand wherever i can, you would not be bothering me in the least by asking questions.
​when you are ready to start tackling the balancing procedure, drop me a line i'll be glad to assist you

 

[Ulma Doctor]

Thank you.
Come May please expect long and tedious interrogatory.
Would this be best as a forum item or as a series of PMs?
Will my endless questions be helpful to others?

Daryl
MN

I'm happy to reply either way is best for you, i'm sure others will have questions that may be answered by our correspondences

 

[Ulma Doctor]

if you need more help or i can even help make one for you, let me know
i'm happy to help out

 

[Uglydog]

I've picked up a used commercially made 20hp RPC several years ago as my Gisholt is 10hp.
I was thinking about a static converter as then I wouldn't need to run 3ph to my wood machine area.... and ..... here's the best part.... my daughter is asking/requesting all the vintage wood machines as she plans her shop. Granted it's a few years out as she finishes up her academic work.
I thought that a static would work well in this application. But, maybe it's not worth the trouble and going directly to a RPC makes more sense?

Daryl
MN