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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#41
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On Oct 19, 6:59*pm, Jamie
t wrote: spamtrap1888 wrote: On Oct 19, 3:14 pm, Jamie t wrote: spamtrap1888 wrote: On Oct 19, 5:09 am, Jeffrey Angus wrote: On 10/17/2011 6:05 PM, Jamie wrote: You know, at this point, you pretty much don't care You're right. I don't. Because my original question was in regards to ampere turns and rewinding a solenoid for a different operating voltage. I wish that that had been your original question, which was a rambling stream of consciousness. Your reference to a program for calculating aircore inductors made me think you were using "solenoid" in the sense of "helical coil." Because so far, with one notable exception, everyone has insisted on coming up with some Rube Goldberg solution or accusing me of trying to murder widows and orphans. Your desire to save $380 in the belief that ASCO was screwing its customers with jacked-up prices seemed a bit unreasonable, the more so when you revealed the true application for the solenoid actuator. But your juryrig would merely produce widows and orphans, not kill them. Only the lineman trying to restore power would be killed if your Rube Goldberg solution failed to work. I must say, you are an idiot! *How is the device itself any less dangerous than using an alternate to operate it? Jamie If the alternate does not operate sufficiently like the original. If he could explain how the actuator works and what the important parameters were, we could speculate as to all the possible failure modes. You can speculate all you want. You sound like an attorney looking for work or closely related to one. * *If you read the blog, you would see what he is using if for, and if he really wants you to know, I am sure he'll refresh your memory. I used to break things for a living. Before that, I had to worry about the adequacy of insulation. From his first post, the guy did not appear to understand much of anything. I hoped he at least would not kill anyone. |
#42
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On 10/19/2011 9:38 PM, spamtrap1888 wrote:
From his first post, the guy did not appear to understand much of anything. I hoped he at least would not kill anyone. Really? Explain how you came to that conclusion. I started with known measured numbers. Worked backwards with a calculator to get the unknown. From there I went forward towards what I thought was correct. Then asked if what I was doing sounded right. I.e. basing the requirements on ampere turns. I even went so far as to include the calculator I used to determine the number turns based on the physical size, DC resistance and measured inductance. So, and unfortunately VERY typical of Usenet, I've had to put up with unfounded personal attacks and a whole plethora of "How you should do anything except what you want to." Jeff-1.0 -- "Everything from Crackers to Coffins" |
#43
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On Oct 16, 4:48*pm, Jeffrey Angus wrote:
Just a few abstract thoughts here. It makes sense to me, but then I've been known to over look the obvious on occasion. ;-) I have a solenoid coil that actuates a large 3-pole contactor. A short pulse to pull up on a lever that will toggle it from on position to another, and back. Making measurements of the solenoid coil, although potted in epoxy, yields a few measurements and a couple of guesses. http://www.pronine.ca/multind.htm Coil form 1" diameter, 1-3/8" width and 1.5" depth. Going backwards on a solenoid coil java script, yields a matching 125 mH inductance (as measured) and 95 ohm DCR (as measured) for 2500 turns of #30 AWG which will fill the bobbin. This a 480 VAC actuator. Am I headed in the right direction if I assume the key factor here is ampere turns? Not allowing for the added inductance by a movable core, this has an impedance of roughly 100 ohms. So that works out to 4.8 amps or 12,000 ampere turns. Substituting 2000 turns of #28 AWG yields 80 mH, and 42 Ohms. And subsequently roughly 12,000 ampere turns at 240 VAC. Putting 240 VAC across the 480 VAC coil yields only 6,000 ampere turns and obviously is NOT enough to actuate the contactor transfer mechanism. The reason I'm curious is that ASCO seems to think that the replacement coil for this is worth $585, although they will sell it as the "sale price" of only $421.80. Jeff-1.0 The other other one -- "Everything from Crackers to Coffins" Hi Jeff, I know nothing about power stuff or soleniod coils. I have made a few open air magnetics. (Usually Helmholtz things) If the size of both air coils is the same, then I believe your calculations are correct. It's only the magnetic field strength that you need to match and that's proportional to number of amp-turns. Wind away I say! George H. |
#44
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On Oct 20, 4:31*pm, George Herold wrote:
On Oct 16, 4:48*pm, Jeffrey Angus wrote: Just a few abstract thoughts here. It makes sense to me, but then I've been known to over look the obvious on occasion. ;-) I have a solenoid coil that actuates a large 3-pole contactor. A short pulse to pull up on a lever that will toggle it from on position to another, and back. Making measurements of the solenoid coil, although potted in epoxy, yields a few measurements and a couple of guesses. http://www.pronine.ca/multind.htm Coil form 1" diameter, 1-3/8" width and 1.5" depth. Going backwards on a solenoid coil java script, yields a matching 125 mH inductance (as measured) and 95 ohm DCR (as measured) for 2500 turns of #30 AWG which will fill the bobbin. This a 480 VAC actuator. Am I headed in the right direction if I assume the key factor here is ampere turns? Not allowing for the added inductance by a movable core, this has an impedance of roughly 100 ohms. So that works out to 4.8 amps or 12,000 ampere turns. Substituting 2000 turns of #28 AWG yields 80 mH, and 42 Ohms. And subsequently roughly 12,000 ampere turns at 240 VAC. Putting 240 VAC across the 480 VAC coil yields only 6,000 ampere turns and obviously is NOT enough to actuate the contactor transfer mechanism. The reason I'm curious is that ASCO seems to think that the replacement coil for this is worth $585, although they will sell it as the "sale price" of only $421.80. Jeff-1.0 The other other one -- "Everything from Crackers to Coffins" Hi Jeff, *I know nothing about power stuff or soleniod coils. *I have made a few open air magnetics. (Usually Helmholtz things) If the size of both air coils is the same, then I believe your calculations are correct. *It's only the magnetic field strength that you need to match and that's proportional to number of amp-turns. *Wind away I say! Driving home, I was thinking that since you're doing a pulsed thing you may care about the L/R time constant. (Is the pulse time much longer than that?) Did 'your' program spit out inductance values too? (Forgive me, I'm too lazy to look for them.) For 'thin' coils you'd expect the inducatance (for the low voltage coil) to go down by four and the resistance to go down by two, so a decrease of two in the time constant... hardly seems like it would matter, unless somethng else in the circuit is expectng it to take longer. For your fat coil the change in time constant is likely even less. George H. George H.- Hide quoted text - - Show quoted text - Oh |
#45
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On 10/20/2011 5:54 PM, George Herold wrote:
Driving home, I was thinking that since you're doing a pulsed thing you may care about the L/R time constant. (Is the pulse time much longer than that?) The pulse is mechanically derived. The small control relay energizes the solenoid. When the solenoid causes the transfer switch to actuate, the auxiliary contacts open the solenoid connection. Jeff-1.0 -- "Everything from Crackers to Coffins" |
#46
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On Wed, 19 Oct 2011 21:32:14 -0500, Jeffrey Angus
wrote: On 10/19/2011 8:39 PM, spamtrap1888 wrote: I see that only the ASCO 4000 and 7000 series are closed-transition switches, i.e. break before make, not the Series 940 -- which I had to look up from the replacement part number you gave. My bad, I suppose. I suppose. The solenoid coil listed is for the series 940. It is also used for several other series. Specifically, in my case, the Series 386 manual transfer switch. And in case you missed it earlier, here is the link for an eBay auction showing picturs of the transfer switch contactor. A similar model. 2-pole 120 VAC rather than 3-pole 480 VAC. http://www.ebay.com/itm/130520617745 And if you go to the partsasco.com website and look up the replacement part numbers for the model 300 or 386, it directs you to the coil marked as being for the series 940. This is the coil itself from ASCO. http://www.ascoparts.com/343500-063.html But again, you're making all sorts of asumption looking to find fault. You've done nothing what so ever to answer the question on rewinding a solenoid to operate at 240 volts rather than 480. Jeff-1.0 Just for grins, Jeff 1.0 have you tried spice models of the rectifier solenoid at 480 and 240? It may help you see something you may have missed. BTW i expect you will replace the bridge with one appropriated rated for the solenoid? ?-) |
#47
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On 10/20/2011 9:51 PM, josephkk wrote:
Just for grins, Jeff 1.0 have you tried spice models of the rectifier solenoid at 480 and 240? It may help you see something you may have missed. It hadn't occurred to me to do that. It's pretty much of a static operation. You apply power, it pulls up on the armature. When the mechanism changes position, an auxiliary switch disconnects the solenoid. BTW i expect you will replace the bridge with one appropriated rated for the solenoid? The original bridge was dealing with 480 vac @ 5.2 amps. The new coil will present a load of about 4 amps @ 240 vac. It's not an issue. Jeff-1.0 -- "Everything from Crackers to Coffins" |
#48
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On Fri, 21 Oct 2011 05:22:39 -0500, Jeffrey Angus
wrote: On 10/20/2011 9:51 PM, josephkk wrote: Just for grins, Jeff 1.0 have you tried spice models of the rectifier solenoid at 480 and 240? It may help you see something you may have missed. It hadn't occurred to me to do that. See where I mumbled: At 60Hz, that's 276 uF. 330uf 600VDC caps should work. I'm not very confident with my crude approximations. Therefore, I would feed the model to LTSpice and see what it's really going to do. http://www.linear.com/designtools/software/#LTspice Look for current and voltage spikes. It's pretty much of a static operation. You apply power, it pulls up on the armature. When the mechanism changes position, an auxiliary switch disconnects the solenoid. You can specify an input pulse with: Syntax: Ixxx n+ n- PULSE(Ioff Ion Tdelay Trise Tfall Ton Tperiod Ncycles) There are also other circuit simulators that might work: http://www.falstad.com/circuit/ (Java) Make me rich and I'll do the recti-fire and sol-e-void model for you. -- # Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060 # 831-336-2558 # http://802.11junk.com # http://www.LearnByDestroying.com AE6KS |
#49
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On Fri, 21 Oct 2011 05:22:39 -0500, Jeffrey Angus
wrote: On 10/20/2011 9:51 PM, josephkk wrote: Just for grins, Jeff 1.0 have you tried spice models of the rectifier solenoid at 480 and 240? It may help you see something you may have missed. It hadn't occurred to me to do that. It's pretty much of a static operation. You apply power, it pulls up on the armature. When the mechanism changes position, an auxiliary switch disconnects the solenoid. I expect you can learn interesting things looking at the current waveforms in the various configurations. BTW i expect you will replace the bridge with one appropriated rated for the solenoid? The original bridge was dealing with 480 vac @ 5.2 amps. The new coil will present a load of about 4 amps @ 240 vac. It's not an issue. That does not make sense for the ampere-turns argument. The number of turns drops dramatically thus the current must increase accordingly. Jeff-1.0 |
#50
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On 10/22/2011 11:55 PM, josephkk wrote:
The original bridge was dealing with 480 vac @ 5.2 amps. The new coil will present a load of about 4 amps @ 240 vac. It's not an issue. That does not make sense for the ampere-turns argument. The number of turns drops dramatically thus the current must increase accordingly. 480v coil 2500 turns @ 4.8 amps 240 coil 2000 turns @ 6.0 amps Jeff-1.0 -- "Everything from Crackers to Coffins" |
#51
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On Sun, 23 Oct 2011 03:36:07 -0500, Jeffrey Angus
wrote: On 10/22/2011 11:55 PM, josephkk wrote: The original bridge was dealing with 480 vac @ 5.2 amps. The new coil will present a load of about 4 amps @ 240 vac. It's not an issue. That does not make sense for the ampere-turns argument. The number of turns drops dramatically thus the current must increase accordingly. 480v coil 2500 turns @ 4.8 amps 240 coil 2000 turns @ 6.0 amps Jeff-1.0 Not as bad of a turns drop as thought. The new numbers make sense. ?-) |
#52
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A follow up to this exercise.
Using 1/16" PVC for the ends and schedule 40 1/2" PVC for the core, I wound 2000 turns of #28 wire on the form and put things together to test them. It works with 240 VAC across the bridge rectifier now. And yes, the coil heats up. It's trying to dissipate 1440 watts. (240 VAC @ 6 amps) The contacts on the transfer switch disconnect the solenoid coil from power as soon as it starts to move. Inertia carries it through the sequence. Jeff-1.0 |
#53
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On Sun, 13 Nov 2011 15:08:29 -0600, Jeffrey Angus
wrote: And yes, the coil heats up. It's trying to dissipate 1440 watts. (240 VAC @ 6 amps) You might want to add a thermal fuse in series with the coil. It the contactor gets stuck in the energized position, you might have a fire. The contacts on the transfer switch disconnect the solenoid coil from power as soon as it starts to move. Inertia carries it through the sequence. That happens it the actuator gets stuck or if the energizing voltage is unusually low? Duz it stick in the "on" state? Worrying about the widows and orphans this might harm... -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#54
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On 11/13/2011 6:19 PM, Jeff Liebermann wrote:
On Sun, 13 Nov 2011 15:08:29 -0600, Jeffrey wrote: And yes, the coil heats up. It's trying to dissipate 1440 watts. (240 VAC @ 6 amps) You might want to add a thermal fuse in series with the coil. It the contactor gets stuck in the energized position, you might have a fire. There is that. See below... The contacts on the transfer switch disconnect the solenoid coil from power as soon as it starts to move. Inertia carries it through the sequence. That happens it the actuator gets stuck or if the energizing voltage is unusually low? Duz it stick in the "on" state? Worrying about the widows and orphans this might harm... See, now this is where everyone got upset over nothing. This whole exercise was to see _IF_ I could correctly wind a replacement solenoid for 240 V rather than the original 480 V. Now that I've satisfied my curiosity, I'm going to sell it in it's original format (480 v 3-phase) as THAT is where it's value lies. Jeff -- "Everything from Crackers to Coffins" |
#55
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On Sun, 13 Nov 2011 20:47:45 -0600, Jeffrey Angus
wrote: This whole exercise was to see _IF_ I could correctly wind a replacement solenoid for 240 V rather than the original 480 V. Now that I've satisfied my curiosity, I'm going to sell it in it's original format (480 v 3-phase) as THAT is where it's value lies. So, this was all an academic exercise, with no practical purpose or monetary value? Had I known, I would have been less helpful and more insulting. You should feel guilty for having wasted my time. For penitence, please either flog yourself, or send me an appropriate percentage of the proceeds. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#56
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On 11/13/2011 10:43 PM, Jeff Liebermann wrote:
send me an appropriate percentage of the proceeds. Fear not fearless leader, I'll remember to cut you in. Jeff-1.0 -- "Everything from Crackers to Coffins" |
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