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Power Factor Correction circuits

Cole2534

Cole2534

Diamond
Joined
Sep 10, 2010
Location
Oklahoma City, OK
In my other thread (https://www.practicalmachinist.com/...-square-wave-355-amp-draw-399703/#post3888693) I learned about how these work and why they're installed.

In the end, it'd be favorable for me (I think?) if I could switch between engaging or disengaging them based on need.

My question is this- short of empirical analysis, how can I tell what voltage these capacitors use to operate and how much amperage can they discharge?

Thought is that if they're less than 600v and 10a I could use a normal 30mm switch and contact blocks to make this work.

I am clearly not an electrical wizard, if I'm way off my rocker that too is an acceptable reply. :)

Here's a pic of the cap in question. It's connected with 12ga wire via 3/8" spade terminals.
51065b401c744ba276b1dc9430d0313a.jpg
 
Cole2534 said:
In the end, it'd be favorable for me (I think?) if I could switch between engaging or disengaging them based on need.
[/IMG]
Click to expand...

Is the need to switch between a free mode to a energy saving mode?

My take-away from using PFC capacitors on my welding machine - unless the machine is constantly in use you will not benefit.
 
With 2 of 3 in place I can squeeze 250a of welding current out of the 50a circuit and have 42a idle load.

With 0 of 3 I can only get to 170a or so before I overload the circuit. That extra 80a can mean a lot.

Programmed via Mazatrol
 
That's a 60uF 460V cap - it says so on the can.

How much current it draws will depend on the grid voltage and frequency. At 240V 60Hz, expect about 5.5A.

Switching capacitors is really rough on switches. Check if the switches/contactors have specific ratings for capacitor use and if not, massively overspec them.
 
Switches won't have cap ratings. Add a thermistor and a time delay fuse in series. Put unswitched 10k bleeder resistors in parallel with each cap so you don't get kil't.

Xc = 1/(2*pi*F*C)

I=E/Z

Z=vector sum of Xl, Xc, and R.
 
SomeoneSomewhere said:
That's a 60uF 460V cap - it says so on the can.

How much current it draws will depend on the grid voltage and frequency. At 240V 60Hz, expect about 5.5A.

Switching capacitors is really rough on switches. Check if the switches/contactors have specific ratings for capacitor use and if not, massively overspec them.
Click to expand...

Or simply switch your caps with the power supply off.....
 
the caps are there for a reason.... and I would be safe to guess that without them, the voltage drops out when you strike an arc and the caps are there to prevent the after voltage spike which could damage other equipment that might be more sensitive in your house power supply.

power spikes kill smaller electronics faster then you can blink and cost you thousands of $$$$$$

just sell it and buy a proper machine instead that is under 200A. new inverters are better.
 
The pf capacitors are connected across the incoming lines on the primary side of a line transformer. If you put bleeder resistors across the caps then they are across
the main ac. What a waste... The caps will discharge thru the transformer windings when power is turned off.

PFC saves electricity when machine is constantly busy with little idle time. So decide how much you will be saving.

Idea that would work but I see it as altering a good machine for a small return.

Use a contactor with four sets of contacts. Use two of them on each side of your PFC caps.
Contactor closes when foot peddle is pressed.
 
rons said:
The pf capacitors are connected across the incoming lines on the primary side of a line transformer. If you put bleeder resistors across the caps then they are across
the main ac. What a waste... The caps will discharge thru the transformer windings when power is turned off.
Click to expand...

The schematic appears to show them downstream of "CR1" a contactor/switch.
 
BT Fabrication said:
the caps are there for a reason.... and I would be safe to guess that without them, the voltage drops out when you strike an arc and the caps are there to prevent the after voltage spike which could damage other equipment that might be more sensitive in your house power supply.

power spikes kill smaller electronics faster then you can blink and cost you thousands of $$$$$$

just sell it and buy a proper machine instead that is under 200A. new inverters are better.
Click to expand...
You seem rather invested with how I handle my machines, and you keep skipping over the fact that this is TEMPORARY in my shop. Before I rearrange a bunch of shit and pull some wire I'd like to make sure I like the machine. Should I not, I have an Invertec and (3) 350mp's. I think I'll be OK.

rons said:
Is the need to switch between a free mode to a energy saving mode?

My take-away from using PFC capacitors on my welding machine - unless the machine is constantly in use you will not benefit.
Click to expand...
All the reading I did on welding web suggested the same. One guy claimed to be an EE and his post read like it.

I have no need to switch, just exploring the possibilities.

And yes, they discharge via the main transformer when the machine is powered off. It says so right in the manual, and then it also gives a procedure for checking them and manually discharging them should something not be properly working.
 
Cole2534 said:
All the reading I did on welding web suggested the same. One guy claimed to be an EE and his post read like it.
Click to expand...

I also researched this about three or four times. Usually when someone asks this type of question I go back and find the same answer: Do not cap the machine.
If you post this in the welding section or ask this type of question on the Miller forum it would not be much different. You can try it and examine your electricity
bill to see what the PFC is doing to you.... I mean for you.

In a time long ago and a land far away, I was a EE. Until I started working for others. Then ....

serf.jpg
 
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