devsterd1
Cast Iron
- Joined
- Jan 12, 2007
- Location
- Norfolk VA
I was wondering if using start caps on 3p motors would be a way to limit in-rush current on start up? Would a VFD do it better? The motors in question are 3-5hp. Any ideas?
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For example, a capacitor in series with an inductor can produce a resonant circuit that develops much higher voltages than the line applied to it. The starter on my 3 hp Roto-Clone dust collector has a 480 V coil. To run it on 240V I connected a 2 mfd capacitor in series. That develops enough voltage to start the pull in. It changes when the contactor closes, but by then it doesn't need the higher voltage to hold it.
Bill
My suggestion is that you get some coaching in basics before trying anything like that.
Bill
That is a very clever way to handle the situation. I like it a lot!
I may have to borrow that method at some point.
Jerry, I hardly have to point this out to you, but to others who may be reading the mail, remember that this requires a "motor run" type capacitor rather than a starting one and the peak voltage on the capacitor will be 679 V or higher, 90 degrees out of phase, but bad power factor voltage can blow a capacitor just as quickly as good. I used an oil filled 1000VDC one like you would see in a high voltage DC supply. Using an electrolytic cap here can demonstrate "unintended consequences" like spitting corrosive juice all over the enclosure.
Bill
...........The starter on my 3 hp Roto-Clone dust collector has a 480 V coil. To run it on 240V I connected a 2 mfd capacitor in series. That develops enough voltage to start the pull in. It changes when the contactor closes, but by then it doesn't need the higher voltage to hold it........
Bill
cool. ur lucky too that supplying 1/2 the v/hz ratio to the motor makes enough HP (3/4hp maybe??) when u remove the cap and run the 480v motor on 240v to run ur particular load!....
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