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+1 on that
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Is This A Static Converter?
- Thread starter Uglydog
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This is what I've used for all of the converters I've built over the years. One addition I do is add a control relay for the bigger motors for handling the capacitor voltage to line 3, so its not going through the push button that you have your finger on.
Ken
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the square d switches used, are rated for 600v,
the control voltage is 240v- the capacitor will not increase the control voltage
a capacitor can't hold a charge greater than the applied voltage
the control voltage is 240v- the capacitor will not increase the control voltage
a capacitor can't hold a charge greater than the applied voltage
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the control voltage is 240v- the capacitor will not increase the control voltage
a capacitor can't hold a charge greater than the applied voltage
A capacitor can't exceed its applied voltage but its applied voltage can easily exceed 240V if it's connected in series with a motor winding while starting it. So it's a good idea to connect a timer or relay to the cap rather than just the push button. Here's a really quick & rough sketch of how I'd wire the controls. Note that this doesn't show any fusing or overload relays.
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All, Thanks for all the help.
Ulmadoc is putting together a care package for the saw.
Additionally, I've got some vintage mills I'll be tearing down and scraping in as needed. With a goal of reselling. I'm hoping to sell them with appropriately sized RPC or worst case statics if that's what buyers would like. I believe that 3ph is a major reason that people are afraid of vintage iron. However, I want to make sure I know what I'm doing!
And yes I've got a couple 1750rpm 3ph motors hanging around with 1-5hp motors. As well as some vintage magnetic starters.
Wire addict: what does "M" and "TR" mean in the diagram?
Is a relay an electronic switch? What do they actually do?
It's my understanding that capacitors hold onto the electricity until its reached a threshold. Then it's released. Does the relay trigger the release creating an impulse timed between the other two impulses.
Or is it a constant flow of electricity, like a garden hose.
And how does a 3ph motor generate the 3leg in a RPC?
I'm hoping to take the time to do more reading on the net and within the HM threads. However, all the threads and lit assumes basic knowledge. Of which I currently have only gaps.
Daryl
MN
Ulmadoc is putting together a care package for the saw.
Additionally, I've got some vintage mills I'll be tearing down and scraping in as needed. With a goal of reselling. I'm hoping to sell them with appropriately sized RPC or worst case statics if that's what buyers would like. I believe that 3ph is a major reason that people are afraid of vintage iron. However, I want to make sure I know what I'm doing!
And yes I've got a couple 1750rpm 3ph motors hanging around with 1-5hp motors. As well as some vintage magnetic starters.
Wire addict: what does "M" and "TR" mean in the diagram?
Is a relay an electronic switch? What do they actually do?
It's my understanding that capacitors hold onto the electricity until its reached a threshold. Then it's released. Does the relay trigger the release creating an impulse timed between the other two impulses.
Or is it a constant flow of electricity, like a garden hose.
And how does a 3ph motor generate the 3leg in a RPC?
I'm hoping to take the time to do more reading on the net and within the HM threads. However, all the threads and lit assumes basic knowledge. Of which I currently have only gaps.
Daryl
MN
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- Feb 2, 2013
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- 3,627
Can you explain how the applied voltage will increase when you connect the capacitor in series?
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On the right side of the sketch I wrote a 1-word description of what "M" & "TR" do; M is the motor starter or contactor coil & TR is the timer coil. & TR is usually a pneumatic timer with an air bleed adjustment which controls the time delay or the time delay can be done electronically, either by counting AC pulses or by charging or discharging a capacitor. In this particular case the timer needs to be an on-delay type where the time delay occurs when the timer coil first energizes.
It's been over 40 years since my AC fundamentals class so I don't remember all the theory & even less of the math involved. Caps cause current to lead the voltage by up to 90 degrees because maximum current through them occurs at maximum voltage & when they're fully discharged so they appear as a short across the voltage source. As they charge the current inrush decreases & the voltage across them increases, however, as the AC voltage crosses zero & reverses polarity, it, & the current discharges the capacitor & then begins to charges it in the opposite direction. Note that the phase shift created here is never over 90 degrees & 3-phase power is 120 degrees so this isn't a perfect solution but it works adequately.
And, no, unfortunately I can't explain how or why the voltage across an inductor or cap in an AC series circuit differ or exceed the applied voltage anymore [I was afraid someone would ask me this!] but I do remember this much: in an L-C series circuit the current through both is equal although the voltages can be different; in an L-C parallel circuit the voltage across both devices is equal but the currents through each can differ. And at resonance I think I recall that voltages are equal across both devices in a series circuit & currents are likewise equal through both devices in a parallel circuit. Hope this helps.
It's been over 40 years since my AC fundamentals class so I don't remember all the theory & even less of the math involved. Caps cause current to lead the voltage by up to 90 degrees because maximum current through them occurs at maximum voltage & when they're fully discharged so they appear as a short across the voltage source. As they charge the current inrush decreases & the voltage across them increases, however, as the AC voltage crosses zero & reverses polarity, it, & the current discharges the capacitor & then begins to charges it in the opposite direction. Note that the phase shift created here is never over 90 degrees & 3-phase power is 120 degrees so this isn't a perfect solution but it works adequately.
And, no, unfortunately I can't explain how or why the voltage across an inductor or cap in an AC series circuit differ or exceed the applied voltage anymore [I was afraid someone would ask me this!] but I do remember this much: in an L-C series circuit the current through both is equal although the voltages can be different; in an L-C parallel circuit the voltage across both devices is equal but the currents through each can differ. And at resonance I think I recall that voltages are equal across both devices in a series circuit & currents are likewise equal through both devices in a parallel circuit. Hope this helps.