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Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work. |
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#1
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Update 2 on Quincy compressor and VFD
I have found approximately 170 microfarads of extra capacitance, in
bits and pieces. Wired them in. Set the V/f curve to linear (setting 0). I set the max frequency to 20 Hz. With that, the compressor spins, runs, pumps, and the motor goes to 33% of its proper RPM. DC Bus Voltage drops from 320 volts to approximately 255 volts when the motor is in action. So it is a little victory, sort of. Trying to set frequency to 25 Hz results in the motor getting stuck and stopped. So, it seems that extra capacitance helps, but I need much more. I have ordered extra capacitors on eBay (electrolytic type, rated at 500 VDC). I hope that maybe 1,000 uF would be about right. Perhaps, for conservatism, I will supply them from a separate rectifier, I have a pair of IRKDL71-06S02 rectifiers. It would be a mess and I would prefer not to do it. i |
#2
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Update 2 on Quincy compressor and VFD
Ignoramus10340 wrote:
... Perhaps, for conservatism, I will supply them from a separate rectifier, I have a pair of IRKDL71-06S02 rectifiers. It would be a mess and I would prefer not to do it. And don't lose sight of your ultimate objective, which is to "flip" this package for a profit. If your eBay listing reads "... with 3 phase VFD modified to run single phase", it might scare off bidders. "Modified" is not a good word to use to describe a VFD. Bob |
#3
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Update 2 on Quincy compressor and VFD
On 2007-10-30, Bob Engelhardt wrote:
Ignoramus10340 wrote: ... Perhaps, for conservatism, I will supply them from a separate rectifier, I have a pair of IRKDL71-06S02 rectifiers. It would be a mess and I would prefer not to do it. And don't lose sight of your ultimate objective, which is to "flip" this package for a profit. If your eBay listing reads "... with 3 phase VFD modified to run single phase", it might scare off bidders. "Modified" is not a good word to use to describe a VFD. You got it. You are right. I will try to do it without extensive modification. I do not consider adding an extra capacitor to be a big modification. i |
#4
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Update 2 on Quincy compressor and VFD
On Tue, 30 Oct 2007 09:44:31 -0400, Bob Engelhardt
wrote: Ignoramus10340 wrote: ... Perhaps, for conservatism, I will supply them from a separate rectifier, I have a pair of IRKDL71-06S02 rectifiers. It would be a mess and I would prefer not to do it. And don't lose sight of your ultimate objective, which is to "flip" this package for a profit. If your eBay listing reads "... with 3 phase VFD modified to run single phase", it might scare off bidders. "Modified" is not a good word to use to describe a VFD. Bob "Custom Fitted with..." Gunner "[L]iberals are afraid to state what they truly believe in, for to do so would result in even less votes than they currently receive. Their methodology is to lie about their real agenda in the hopes of regaining power, at which point they will do whatever they damn well please. The problem is they have concealed and obfuscated for so long that, as a group, they themselves are no longer sure of their goals. They are a collection of wild-eyed splinter groups, all holding a grab-bag of dreams and wishes. Some want a Socialist, secular-humanist state, others the repeal of the Second Amendment. Some want same sex/different species marriage, others want voting rights for trees, fish, coal and bugs. Some want cradle to grave care and complete subservience to the government nanny state, others want a culture that walks in lockstep and speaks only with intonations of political correctness. I view the American liberals in much the same way I view the competing factions of Islamic fundamentalists. The latter hate each other to the core, and only join forces to attack the US or Israel. The former hate themselves to the core, and only join forces to attack George Bush and conservatives." --Ron Marr |
#5
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Update 2 on Quincy compressor and VFD
In article ,
Ignoramus1285 wrote: On 2007-10-30, Bob Engelhardt wrote: Ignoramus10340 wrote: ... Perhaps, for conservatism, I will supply them from a separate rectifier, I have a pair of IRKDL71-06S02 rectifiers. It would be a mess and I would prefer not to do it. And don't lose sight of your ultimate objective, which is to "flip" this package for a profit. If your eBay listing reads "... with 3 phase VFD modified to run single phase", it might scare off bidders. "Modified" is not a good word to use to describe a VFD. You got it. You are right. I will try to do it without extensive modification. I do not consider adding an extra capacitor to be a big modification. If you are adding capacitors to a VFD that is designed to accommodate just that, you are not modifying the VFD. Joe Gwinn |
#6
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Update 2 on Quincy compressor and VFD
now you just have to find a buyer that wants a compressor with a VFD drive,
and is willing to pay extra for it. If their shop has 3 phase already....... "Ignoramus10340" wrote in message ... I have found approximately 170 microfarads of extra capacitance, in bits and pieces. Wired them in. Set the V/f curve to linear (setting 0). I set the max frequency to 20 Hz. With that, the compressor spins, runs, pumps, and the motor goes to 33% of its proper RPM. DC Bus Voltage drops from 320 volts to approximately 255 volts when the motor is in action. So it is a little victory, sort of. Trying to set frequency to 25 Hz results in the motor getting stuck and stopped. So, it seems that extra capacitance helps, but I need much more. I have ordered extra capacitors on eBay (electrolytic type, rated at 500 VDC). I hope that maybe 1,000 uF would be about right. Perhaps, for conservatism, I will supply them from a separate rectifier, I have a pair of IRKDL71-06S02 rectifiers. It would be a mess and I would prefer not to do it. i |
#7
Posted to rec.crafts.metalworking
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Update 2 on Quincy compressor and VFD
Ignoramus10340 wrote:
I have found approximately 170 microfarads of extra capacitance, in bits and pieces. Wired them in. Set the V/f curve to linear (setting 0). I set the max frequency to 20 Hz. With that, the compressor spins, runs, pumps, and the motor goes to 33% of its proper RPM. DC Bus Voltage drops from 320 volts to approximately 255 volts when the motor is in action. That proves the problem is where we expected it to be. But, 255 V is still really low. You should be able to develop 90 V RMS at that cap voltage (half of 255/1.414). Hmmm, (90/240) * 60 Hz = 22.5 Hz, so that is right on the money, too. So it is a little victory, sort of. Trying to set frequency to 25 Hz results in the motor getting stuck and stopped. So, it seems that extra capacitance helps, but I need much more. I have ordered extra capacitors on eBay (electrolytic type, rated at 500 VDC). I hope that maybe 1,000 uF would be about right. Well, you need a hold-up time of about 8 ms, and the line current for 10 Hp at 340 VDC is about 22 A, so 1000 uf (0.001 F) will sag at a rate of 22,000 V/sec. Ugh, if I did this right, it will still lose 176 V between line peaks. This doesn't sound right, but I don't see my error. Increasing the cap bank to 5000 uF (wow, that's a lot of caps at 500 V) would reduce the sag to about 34 V, which is probably the kind of voltage ripple you are aiming for (~10%). Jon |
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