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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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Older DC fractional HP motors
Many of such motors with wound fields required 90 volts for the field.
Why 90 volts and how was it derived? thanks, CP |
#2
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Older DC fractional HP motors
On Sun, 2 Apr 2017 19:27:38 -0700, MOP CAP wrote:
Many of such motors with wound fields required 90 volts for the field. Why 90 volts and how was it derived? thanks, CP Some had field rheostats for speed control. As for the 90 volts, likely the output voltage of a rectified line voltage using the rectifier technology and line voltage of the time. |
#3
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Older DC fractional HP motors
On Sun, 02 Apr 2017 22:42:36 -0400, clare wrote:
On Sun, 2 Apr 2017 19:27:38 -0700, MOP CAP wrote: Many of such motors with wound fields required 90 volts for the field. Why 90 volts and how was it derived? thanks, CP Some had field rheostats for speed control. As for the 90 volts, likely the output voltage of a rectified line voltage using the rectifier technology and line voltage of the time. 90V probably became standard at some time in the dim past for reasons that haven't applied since 1920, but has been carried forward because it's a standard. Just a guess, but you stumble across that sort of thing all the time. -- Tim Wescott Control systems, embedded software and circuit design I'm looking for work! See my website if you're interested http://www.wescottdesign.com |
#4
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Older DC fractional HP motors
On Sun, 02 Apr 2017 22:42:36 -0400, clare wrote:
On Sun, 2 Apr 2017 19:27:38 -0700, MOP CAP wrote: Many of such motors with wound fields required 90 volts for the field. Why 90 volts and how was it derived? thanks, CP Some had field rheostats for speed control. As for the 90 volts, likely the output voltage of a rectified line voltage using the rectifier technology and line voltage of the time. Just as a guess, when you expect 120 VAC, you may only receive down to 70 from service for various reasons (due to back-up generators, peak/off-peak, voltage drops, over/under-voltages, surges, etc..), so you still want the thing to crank. |
#5
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Older DC fractional HP motors
"Tim Wescott" wrote in message
... On Sun, 02 Apr 2017 22:42:36 -0400, clare wrote: On Sun, 2 Apr 2017 19:27:38 -0700, MOP CAP wrote: Many of such motors with wound fields required 90 volts for the field. Why 90 volts and how was it derived? thanks, CP Some had field rheostats for speed control. As for the 90 volts, likely the output voltage of a rectified line voltage using the rectifier technology and line voltage of the time. 90V probably became standard at some time in the dim past for reasons that haven't applied since 1920, but has been carried forward because it's a standard. Just a guess, but you stumble across that sort of thing all the time. -- Tim Wescott Control systems, embedded software and circuit design I'm looking for work! See my website if you're interested http://www.wescottdesign.com This describes 90VDC motors as suitable for thyristor-regulated rectified 120VAC. http://www.leeson.com/Literature/pdf/b1600IEC.pdf The mercury vapor tubes used as high power rectifiers before comparable silicon diodes became available dropped around 15V. -jsw |
#6
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Older DC fractional HP motors
On Mon, 03 Apr 2017 07:18:05 -0400, Jim Wilkins wrote:
"Tim Wescott" wrote in message ... On Sun, 02 Apr 2017 22:42:36 -0400, clare wrote: On Sun, 2 Apr 2017 19:27:38 -0700, MOP CAP wrote: Many of such motors with wound fields required 90 volts for the field. Why 90 volts and how was it derived? thanks, CP Some had field rheostats for speed control. As for the 90 volts, likely the output voltage of a rectified line voltage using the rectifier technology and line voltage of the time. 90V probably became standard at some time in the dim past for reasons that haven't applied since 1920, but has been carried forward because it's a standard. Just a guess, but you stumble across that sort of thing all the time. -- Tim Wescott Control systems, embedded software and circuit design I'm looking for work! See my website if you're interested http://www.wescottdesign.com This describes 90VDC motors as suitable for thyristor-regulated rectified 120VAC. http://www.leeson.com/Literature/pdf/b1600IEC.pdf The mercury vapor tubes used as high power rectifiers before comparable silicon diodes became available dropped around 15V. -jsw Hmm. That sounds about right if you used the field coil as the inductor in a choke-input "filter". -- Tim Wescott Wescott Design Services http://www.wescottdesign.com I'm looking for work -- see my website! |
#8
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Older DC fractional HP motors
Depends on the tube. I have vacuum tubes that pass 1000 amps to the
plate. About the size of your for-arm. Mil grade. Then the real nasty ones for plating and welding - Ignatrons (sp) that are mercury filled in a pool to splatter 10's of thousands of amps. The big tubes I have are gas filled and were motor controls. Took two on each motor and there were 3 motors to spin a very large triangle antenna. Martin On 4/3/2017 9:12 PM, DoN. Nichols wrote: On 2017-04-03, wrote: On Sun, 2 Apr 2017 19:27:38 -0700, MOP CAP wrote: Many of such motors with wound fields required 90 volts for the field. Why 90 volts and how was it derived? thanks, CP Some had field rheostats for speed control. As for the 90 volts, likely the output voltage of a rectified line voltage using the rectifier technology and line voltage of the time. With modern rectifiers (silicon ones) that would work out to about 64 VRMS. But vacuum tube rectifiers would have a lot more series resistance, so that might work out with 110 VAC (the old line voltage, which then jumped to 115 VAC, then 117 VAC, and now 120 VAC.) (And the frequency used to be specified as Cycles-Per_Second (CPS) or '~' instead of Hz. :-) Also -- the rectifier was likely not used with filter capacitors, so the RMS value of a half-wave rectified 110 VAC might be pretty close to that. Enjoy, DoN. |
#9
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Older DC fractional HP motors
On Mon, 3 Apr 2017 07:18:05 -0400, "Jim Wilkins"
wrote: "Tim Wescott" wrote in message ... On Sun, 02 Apr 2017 22:42:36 -0400, clare wrote: On Sun, 2 Apr 2017 19:27:38 -0700, MOP CAP wrote: Many of such motors with wound fields required 90 volts for the field. Why 90 volts and how was it derived? thanks, CP Some had field rheostats for speed control. As for the 90 volts, likely the output voltage of a rectified line voltage using the rectifier technology and line voltage of the time. 90V probably became standard at some time in the dim past for reasons that haven't applied since 1920, but has been carried forward because it's a standard. Just a guess, but you stumble across that sort of thing all the time. -- Tim Wescott Control systems, embedded software and circuit design I'm looking for work! See my website if you're interested http://www.wescottdesign.com This describes 90VDC motors as suitable for thyristor-regulated rectified 120VAC. http://www.leeson.com/Literature/pdf/b1600IEC.pdf The mercury vapor tubes used as high power rectifiers before comparable silicon diodes became available dropped around 15V. -jsw Absolutely correct. Gunner --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus |
#10
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Older DC fractional HP motors
On 4 Apr 2017 02:12:18 GMT, "DoN. Nichols"
wrote: On 2017-04-03, wrote: On Sun, 2 Apr 2017 19:27:38 -0700, MOP CAP wrote: Many of such motors with wound fields required 90 volts for the field. Why 90 volts and how was it derived? thanks, CP Some had field rheostats for speed control. As for the 90 volts, likely the output voltage of a rectified line voltage using the rectifier technology and line voltage of the time. With modern rectifiers (silicon ones) that would work out to about 64 VRMS. But vacuum tube rectifiers would have a lot more series resistance, so that might work out with 110 VAC (the old line voltage, which then jumped to 115 VAC, then 117 VAC, and now 120 VAC.) (And the frequency used to be specified as Cycles-Per_Second (CPS) or '~' instead of Hz. :-) Also -- the rectifier was likely not used with filter capacitors, so the RMS value of a half-wave rectified 110 VAC might be pretty close to that. Voltages might have started out (in the Dark Ages?) at 110vac, but they were 115v in my teens and are 120/240vac nowadays. It has been that way for a long time. I was thinking that rectification caused the drop to warrant building 90v and 180v DC motors. -- That's the thing about needs. Sometimes, when you get them met, you don't need them anymore. -- Michael Patrick King |
#11
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Older DC fractional HP motors
Larry Jaques wrote:
On 4 Apr 2017 02:12:18 GMT, "DoN. Nichols" wrote: On 2017-04-03, wrote: On Sun, 2 Apr 2017 19:27:38 -0700, MOP CAP wrote: Many of such motors with wound fields required 90 volts for the field. Why 90 volts and how was it derived? thanks, CP Some had field rheostats for speed control. As for the 90 volts, likely the output voltage of a rectified line voltage using the rectifier technology and line voltage of the time. With modern rectifiers (silicon ones) that would work out to about 64 VRMS. But vacuum tube rectifiers would have a lot more series resistance, so that might work out with 110 VAC (the old line voltage, which then jumped to 115 VAC, then 117 VAC, and now 120 VAC.) (And the frequency used to be specified as Cycles-Per_Second (CPS) or '~' instead of Hz. :-) Also -- the rectifier was likely not used with filter capacitors, so the RMS value of a half-wave rectified 110 VAC might be pretty close to that. Voltages might have started out (in the Dark Ages?) at 110vac, but they were 115v in my teens and are 120/240vac nowadays. It has been that way for a long time. I was thinking that rectification caused the drop to warrant building 90v and 180v DC motors. 120VAC*.707=84.84V Average, unfilterd DC -- Never **** off an Engineer! They don't get mad. They don't get even. They go for over unity! ;-) |
#12
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Older DC fractional HP motors
On 2017-04-05, Michael A. Terrell wrote:
Larry Jaques wrote: On 4 Apr 2017 02:12:18 GMT, "DoN. Nichols" wrote: [ ... ] With modern rectifiers (silicon ones) that would work out to about 64 VRMS. But vacuum tube rectifiers would have a lot more series resistance, so that might work out with 110 VAC (the old line voltage, which then jumped to 115 VAC, then 117 VAC, and now 120 VAC.) (And the frequency used to be specified as Cycles-Per_Second (CPS) or '~' instead of Hz. :-) Also -- the rectifier was likely not used with filter capacitors, so the RMS value of a half-wave rectified 110 VAC might be pretty close to that. Voltages might have started out (in the Dark Ages?) at 110vac, but they were 115v in my teens and are 120/240vac nowadays. It has been that way for a long time. I was thinking that rectification caused the drop to warrant building 90v and 180v DC motors. 120VAC*.707=84.84V Average, unfilterd DC That sounds wrong. The 0.707 multiplier is applied to the peak voltage (170V) to get to the 120 VAC rating. Applying it again to the result just feels wrong. :-) However, if you are half-wave rectifying, with no filtration capacitors, the RMS (Root-Mean-Square) value of that half cycle, followed by another half-cycle of time, could be pretty close to the 90V rating for the field. O.K. -- Looking in this site: http://www.daycounter.com/Calculators/RMS-Calculator.phtml gives this for a half-wave rectified value: ================================================== ==================== Half rectified wave Vrms= Vpk/2 ================================================== ==================== so -- for the 170 V Peak, we get 85V RMS so -- 90 V field allows for a surge of 127 VRMS ac -- so a worst-case value. Enjoy, DoN. -- Remove oil spill source from e-mail Email: | (KV4PH) Voice (all times): (703) 938-4564 (too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html --- Black Holes are where God is dividing by zero --- |
#13
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Older DC fractional HP motors
On Tue, 4 Apr 2017 21:18:40 -0400, "Michael A. Terrell"
wrote: Larry Jaques wrote: On 4 Apr 2017 02:12:18 GMT, "DoN. Nichols" wrote: On 2017-04-03, wrote: On Sun, 2 Apr 2017 19:27:38 -0700, MOP CAP wrote: Many of such motors with wound fields required 90 volts for the field. Why 90 volts and how was it derived? thanks, CP Some had field rheostats for speed control. As for the 90 volts, likely the output voltage of a rectified line voltage using the rectifier technology and line voltage of the time. With modern rectifiers (silicon ones) that would work out to about 64 VRMS. But vacuum tube rectifiers would have a lot more series resistance, so that might work out with 110 VAC (the old line voltage, which then jumped to 115 VAC, then 117 VAC, and now 120 VAC.) (And the frequency used to be specified as Cycles-Per_Second (CPS) or '~' instead of Hz. :-) Also -- the rectifier was likely not used with filter capacitors, so the RMS value of a half-wave rectified 110 VAC might be pretty close to that. Voltages might have started out (in the Dark Ages?) at 110vac, but they were 115v in my teens and are 120/240vac nowadays. It has been that way for a long time. I was thinking that rectification caused the drop to warrant building 90v and 180v DC motors. 120VAC*.707=84.84V Average, unfilterd DC See? It's safe for a 90vdc motor. -- That's the thing about needs. Sometimes, when you get them met, you don't need them anymore. -- Michael Patrick King |
#14
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Older DC fractional HP motors
On Tue, 4 Apr 2017 21:18:40 -0400, "Michael A. Terrell"
wrote: Larry Jaques wrote: On 4 Apr 2017 02:12:18 GMT, "DoN. Nichols" wrote: On 2017-04-03, wrote: On Sun, 2 Apr 2017 19:27:38 -0700, MOP CAP wrote: Many of such motors with wound fields required 90 volts for the field. Why 90 volts and how was it derived? thanks, CP Some had field rheostats for speed control. As for the 90 volts, likely the output voltage of a rectified line voltage using the rectifier technology and line voltage of the time. With modern rectifiers (silicon ones) that would work out to about 64 VRMS. But vacuum tube rectifiers would have a lot more series resistance, so that might work out with 110 VAC (the old line voltage, which then jumped to 115 VAC, then 117 VAC, and now 120 VAC.) (And the frequency used to be specified as Cycles-Per_Second (CPS) or '~' instead of Hz. :-) Also -- the rectifier was likely not used with filter capacitors, so the RMS value of a half-wave rectified 110 VAC might be pretty close to that. Voltages might have started out (in the Dark Ages?) at 110vac, but they were 115v in my teens and are 120/240vac nowadays. It has been that way for a long time. I was thinking that rectification caused the drop to warrant building 90v and 180v DC motors. 120VAC*.707=84.84V Average, unfilterd DC Is that the constant for a gas rectifier tube, or a selenium stack? |
#15
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Older DC fractional HP motors
On 2017-04-05, Gunner wrote:
On Tue, 4 Apr 2017 21:18:40 -0400, "Michael A. Terrell" wrote: Larry Jaques wrote: On 4 Apr 2017 02:12:18 GMT, "DoN. Nichols" wrote: 120VAC*.707=84.84V Average, unfilterd DC Is that the constant for a gas rectifier tube, or a selenium stack? Actually, it is the result of a pure rectifier -- no voltage drop, so any real rectifier would have more drop. All of these are larger drops than typical silicon rectifiers of today -- at least until you get to seriously high voltages, which would have a number of silicon junctions in series (at about 0.7V each) with resistors in parallel to keep the reverse voltage evenly divided. But in essence, any half-wave rectifier would produce voltages safe for the motor. Stay clear of full-wave bridges, however, or filter capacitors. :-) Enjoy, DoN. -- Remove oil spill source from e-mail Email: | (KV4PH) Voice (all times): (703) 938-4564 (too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html --- Black Holes are where God is dividing by zero --- |
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