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Re: Rich tells us how to Ram 300+ A through a 40 A breaker.
Robert B. Bonner
You guys are killing me.
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BOB DD -----Original Message-----
From: ham_amplifiers@... [mailto:ham_amplifiers@...] On Behalf Of pentalab Sent: Monday, November 20, 2006 12:29 AM To: ham_amplifiers@... Subject: [ham_amplifiers] Rich tells us how to Ram 300+ A through a 40 A breaker. --- In ham_amplifiers@..., R L Measures <r@...> wrote: Ohm's Law. The calc. peak mains current was c. 300A. The measured result was 1200v- pk into 50-ohms on SSB. ### 1200 V pk equates to 14,396 watts pep output into a 50 ohm load....14,395.65 /.63 = 22,850 w dc input. Primary VA = 22,850 x 1.22 = 27,877 va 27,877 /240v = 116.155 A .... not including fil xfmr, blower etc. Peak current is aprx 375A with big wire and a big C filter... every 8.3 msecs. ### Rich... tell us how you take a steady state plate and grid current meter readings..... with out blowing ur under rated 40 A house breaker ???? IE: a dead cxr... for just 3-6 seconds... just long enough to measure grid/plate current + fil V, loaded plate V, etc. Forget the fil v/ plate v...... focus on just the plate + grid current. ### If u just pulse tune it...and talk...fine... I do too. Unless both ur plate/grid meter's are peak reading types.... I can't see how it's done. ### IMO.. the entire system should be configured to at least handle a 4-7 second dead cxr.... without blowing breakers, melting coax, frying tank coils etc. ### For a 8170/8171.... I'd use a 100A breaker... and a bare min of 2 ga wire... and considering the 300-400A peak current draw every 8.3 msec..... 3 x 000 CU is the real ticket.... regardless of length. ### BTW... what's the CCS rating of the SB-220's plate xfmr ??? I heard it was 1200 va. Now Rich has stated it's only 600Va. I'm sure the smaller SB-200 is 600 va CCS. ### Will a SB-220 stock... in good condition, on low plate V...be capable of delivering 600W CCS RTTY ??? If so... the plate xfmr would have to be a 1200 va unit. Later... Jim VE7RF R L Measures, AG6K, 805.386.3734 Yahoo! Groups Links |
Re: AC HiPot tester question
On Nov 20, 2006, at 5:11 AM, Harold Mandel wrote:
At the potential required to effect a change the resulting amperage might beThis could be interesting, Hal. R L Measures, AG6K, 805.386.3734 r@..., rlm@..., www.somis.org |
Re: AC HiPot tester question
On Nov 20, 2006, at 4:56 AM, Mike Sawyer wrote:
I have done this, Mike, but one must be careful not to overdo the procedure. To begin with, connect a 20M to 100M HV-rated resistor in series with the high-potential tester to seriously limit current. . . When a vacuum-C has been in storage for a long time, it is not unusual to find that as applied potential rises, it will "tink" (indicating a flashover) briefly discharging the cap several kV below its rated peak-V. This does not mean that the cap is feculent. By slowing raising the applied potential until the cap tinks, Cu whiskers can be burned off, raising the cap's piv each time the procedure is repeated. However, at some point in the tinling procedure, the piv will begin to DEcrease -- i. e., the procedure becomes destructive rather than constructive. IOW, this is yet another case where mo' is Not always mo' betta. It is my opinion the 3 or 4 tinks is about the limit. cheerz ...R L Measures, AG6K, 805.386.3734 r@..., rlm@..., www.somis.org |
Re: Fried glitch R...... from an oversized HV fuse
On Nov 19, 2006, at 10:04 PM, pentalab wrote:
--- In ham_amplifiers@..., R L Measures <r@...> wrote:The critical thing is: at what potential does the unit begin to conduct current.the 250v-rated MOV's, Jim. Depending on who makes a MOV.... clamp V is alwaysIn the 8169 / Plywood Box #2 amplifier, I deliberately used a HV rectifier safety factor of 33% based on my measurement of the actual PIV. There has never been a failure. You seem to assume that conduction for a 250v rating begins at 251 x 1.14 volts. It does not. A few too manyBe there, done that. 1000J is pretty nasty. Way too many housechortle. My guess is that Joslyn has yet to try measuring the zener- v of a 250V rated MOV. ...later R L Measures, AG6K, 805.386.3734 r@..., rlm@..., www.somis.org |
Re: Fried glitch R...... from an oversized HV fuse
On Nov 20, 2006, at 2:34 AM, pentalab wrote:
--- In ham_amplifiers@..., R L Measures <r@...> wrote:Precisely, but so far never has.the 8170 amp.The point here is.... by oversizing the HV fuse.... the load isRICH SEZ... Which is why I used a 40A thermal-magnetic breaker for since weWe? YOU assumed that I was stupid enough to do this. WouldA 1 significant digit reading does not imply great gobs of accuracy. I measure low resistances by putting 1.000A through them and measuring the mV drop with my Fluke DMM. The glitch R begins to limit fault current in no time, and it's peak current that does the damage. ...R L Measures, AG6K, 805.386.3734 r@..., rlm@..., www.somis.org |
Re: AC HiPot tester question
On Nov 20, 2006, at 12:17 AM, pentalab wrote:
--- In ham_amplifiers@..., R L Measures <r@...> wrote:.. and Tom Rauch?over-...RICH SEZ.... A 20kV rated C to block 7000V DC sounds likeisengineering since the actual AC potential across the blocker####### The AC potential across the cap has nothing to do withminimal. RICH SEZ...and it does not make good senseI have seen whisker growth in vacuum caps that have been in long-term storage. However, when such caps are high-potted, after a few tinks the stickers apparently burn off and the piv capability returns. DROPS...hence size the caps DC HV rating at least 3 x the plateSo why does the Jennings Vacuum and Gas Capacitor catalog say on p.6: "DC -- Vacuum capacitors should not be operated in DC applications above the peak RF working voltage." "DC Plus RF -- For DC plus RF applications, the sum of the DC plus the peak RF voltage should not exceed the peak RF working voltage." that's what Eimac sez... that's what 11m ops say... or else it'shardly. Page 6 still has you by the short hair. Johnny's dead, I'm not quite there yet - despite the plenitude of fervent prayers of Mormons, Muslims, Jehovah's Witnesses, SDAs, and Roman Catholics. . - prima facie - adv. 1. At first sight; before closer inspection: They had, prima facie, a legitimate complaint. Page 6. The Vacuum and Gas Capacitor Catalog: "RF Working Voltage is the maximum RF voltage that can be applied to the capacitor without affecting its ability to withstand instantaneous overloads, It is generally 60% of the Peak Test Voltage rating. ..." They are asuming and also implying you haveStaying below the peak RF WV ability is the prime concern no matter the application. What they are refering too isAgreed According to page 6, "DC Plus RF -- For DC plus RF applications, the sum of the DC plus the peak RF voltage should not exceed the peak RF working voltage." Example -- A 1000pF DC blocker, using an 8281 running at 10.5kV with a typical tank Q, would have c. 20A of tank circulating current flowing through the DC blocker at 29MHz, so there would be c. 105volts drop across it. Thus, according to p.6, a capacitor with 10,500v plus 105v = 10,605 / 0.60, so a 17,500 DC-test V or higher unit should be used. However, amplifiers with 10,500v anode supplies are not all that common in Hamdom. Also, 10,500v is getting pretty close to the land of x-rays. reactance. 176- ohms of XC and a RL of 176-ohms x 5 = 880-ohms or...RICH SEZ.... The rule of thumb is a 5 to one ratio for a couplingRICH SEZ... I do, Jim. Even 500pF is plenty for a DC blocker at1.8MHz (XC = 190- ohms) in typical amplifiers since RL is in the Where did the 1.5A come from? ...How did you calculate this, Jim?in a 3x3### a 100 pf plate block doorknob cap wouldn't last 30 seconds#### lemme see. With say 2.5 A of plate current at 5 kv under A HT-57 100 pf cap is only rated at 13.7 A @to be continued ... R L Measures, AG6K, 805.386.3734 r@..., rlm@..., www.somis.org |
Re: AC HiPot tester question
Harold Mandel
At the potential required to effect a change the resulting amperage might be
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deleterious. Why not e-mail Jennings to see their fix? Hal W4HBM -----Original Message-----
From: ham_amplifiers@... [mailto:ham_amplifiers@...] On Behalf Of Mike Sawyer Sent: Monday, November 20, 2006 7:57 AM To: ham_amplifiers@... Subject: Re: [ham_amplifiers] Re: AC HiPot tester question Now, let me ask a question of social and political importance: Is it possible to 'remove' the whisker by introducing and hi(er)-voltage to the vacuum cap? The reason I ask is that this was practice used to recover Ni-Cad batteries. A whisker would develop between anode and cathode and a charge capacitor, several times the actual output of the cell would be placed across it, (reversed polarity if memory serves me), and physically 'burn' the offending whisker. Mod-U-Lator, Mike(y) W3SLK ----- Original Message ----- From: craxd <mailto:craxd@...> To: ham_amplifiers@... <mailto:ham_amplifiers@...> Sent: Monday, November 20, 2006 12:29 AM Subject: [ham_amplifiers] Re: AC HiPot tester question It sounds to me that Jennings wants things two different ways. First they say don't momentarily test a vacuum cap with DC, but it's okay to put one in service as a DC blocking cap, de-rated or not. From everything I've ever read, the whisker problem is caused over time, not in one minute of use. A DC blocker cap could be in an amp for a lifetime. That's a good sales gimmick to sell hipots though. I've never seen that warning either by Comet, or by any of the Russian manufactured caps. If the cause is over the copper being too soft used for the plate cups, it ought to be changed to a hard copper or an alloy to stop it. I can see soft copper for the bellows, but not the plate cups. Thank God Rich and I didn't question the Jennings engineers on the other list as we would have been sent another e-mail by the unknown admin chastizing us for ever questioning these professionals with published papers, etc.... Best, Will --- In ham_amplifiers@... <mailto:ham_amplifiers%40yahoogroups.com> , R L Measures <r@...> wrote: <mailto:ham_amplifiers%40yahoogroups.com> , R L Measures <r@...> wrote: 190-So why does the statement I quoted in the Jennings catalog on p.4engineering since the actual AC potential across the blocker is ohms) in typical amplifiers since RL is in the kilo-ohms range.expected11m ops don't need much C for 11m... 100-250 pf maxTom Rauch apparently knows a Ham who mistakenly used a 100pF DC output from 1.8 to 28 MHz. Sometime later, when a friend wasbeing shown the amplifier, he noticed that there were only twp zerosafter the 1 on the blocker cap. When a 1000pF cap was substituted forthe 100pF cap, the output did not increase although the tuning changed |
Re: AC HiPot tester question
Mike Sawyer
¿ªÔÆÌåÓýNow, let me ask a question of social and political importance: Is it
possible to 'remove' the whisker by introducing and hi(er)-voltage to the vacuum
cap? The reason I ask is that this was practice used to recover Ni-Cad
batteries. A whisker would develop between anode and cathode and a charge
capacitor, several times the actual output of the cell would be placed across
it, (reversed polarity if memory serves me), and physically 'burn' the offending
whisker.
Mod-U-Lator, Mike(y) W3SLK ----- Original Message -----
From: craxd
Sent: Monday, November 20, 2006 12:29 AM
Subject: [ham_amplifiers] Re: AC HiPot tester question It sounds to me that Jennings wants things two different ways. First |
Re: Rich tells us how to Ram 300+ A through a 40 A breaker.
On Nov 19, 2006, at 10:28 PM, pentalab wrote:
--- In ham_amplifiers@..., R L Measures <r@...> wrote:CorrectOhm's Law. The calc. peak mains current was c. 300A. The ..14,395.65 /.63 = 22,850 w dc input.My guess is that the efficiency was closer to 60%. Primary VA = 22,850Only if one assumes that the filter-C stores zero Joules in the 70% interim between 30pps, 30% duty-cycle tuning pulses. . .... notThe mains ESR was measured at 0.079¦¸, add 200' of #4 Cu. Xfmr pri. R = 0.075¦¸, sec R = 12¦¸, and the turns ratio is 240/3000 = 12.5. I came up c. 300A-pk - which could have been in the ballpark since my wife could hear the wires vibrate in the attic when I tuned the sucker up. For designed-for-SSB amplifiers, I don't. The plate/anode current meter is used only to adj. ZSAC. During speech, it probably indicated c. 1/3 of the anode current, or perhaps 1.3 A. . . After adjusting for zero grid-current and 0.5A of ZSAC, and tuning-loading for the specified screen-current I was done with meter readings. The next step was optional -- to measure peak-V into 50-ohms with an oscilloscope and a HV multiplier probe. .... with out blowing ur under rated 40 AWith an amplifier that was designed for SSB-only, only a dead-head would use a dead-carrier. Easy: grid current is zero, ZSAC is whatever is specified, with a 30% duty-cycle tuning-pulser, multiply the screen-current reading by 3.3. For example, normal screen-current is 120ma, so when the meter peaks at 36mA with the Tune-C control, the 8170 or 8171 is ready for use. To have been able to go on the A0 trip would have required a HV transformer that weighed and cost triple, plus the added cost of 200' of #2 Cu. The total cost for the Plywood Box 8170 project was $1200, not counting the 200' of #4 Cu for the 240v 50a outlet. For RTTY, this makes sense, but for SSB, it's greenbacks flushed down the crapper. It's not speced, Jim, but the core dimensions figure out to c. 550w. Now Rich has stated it's onlyI have no idea, Jim. Continuous broadcasting is something I have zero interest in. later ...R L Measures, AG6K, 805.386.3734 r@..., rlm@..., www.somis.org |
Re: Fried glitch R...... from an oversized HV fuse
pentalab
--- In ham_amplifiers@..., R L Measures <r@...> wrote:
the 8170 amp.The point here is.... by oversizing the HV fuse.... the load isRICH SEZ... Which is why I used a 40A thermal-magnetic breaker for #### Which will be on the ragged edge of opening... since we already determined you are sucking 110 A on keydown cxr. Would be kind of nice to run a dead cxr..for at least 3-7 seconds.. just to take steady state plate/grid current readings. You can't do that with a 40 A breaker. With a 2 x pole [50 A per pole] breaker.. with it's poles wired in parallel.. and tie bar removed... and 2 x such assys' used... one per hot leg... u can then have all 4 poles activated for dead cxr stuff... and kick one pole off per breaker... for ragged edge ssb operation. IE: toggle from a 100 A breaker... down to a 50 A breaker. ### with a B+K 875-B... also used a HP DVM [very expensiveRICH SEZ...How did you measure this?BTW... that Dahl A-540 hypersil C core 253 lb plate xfmr I box... just back from the cal lab, reads some extra zero's] The Fluke 87 will only read to 1/10ths of an ohm. Also, low resistance readings can be even more accurately done using mho's/ siemens. .01 ohm = 100 mho's. .001 ohm = 1000 mho's .0001 ohm = 10,000 mho's. I have gear that will read higher than 10,000 mho's. In all cases... the sec was shorted, when taking pri readings... and vice versa.. when taking sec readings. RICH SEZ... Thus, my guess is that the short-circuit current would be c. 470A-rms. The secondary current under a short would be 470A / 21.6 = 21.7A-rms. Jim: Why would a HV fuse in the secondary be better than a250V fuse in the primary? ### Cuz a 3 A sandfilled fuse.. with 8 kv/50 ohm glitch = 160 A of fault current. 160A of fault current has a tendency to blow a HV sand fuse in < 2 msecs. Fast 100 A fuses in the primary would work... but with 470 A... would not open as fast. Only 1 x HV fuse needed..... VS TWO x 100 A high speed fuses in 240 v primary. applied, does the glitch R survive?.... LOADS... as my buddy with the same 253 lb xfmrRICH SEZ.... When a correct size HV fuse is used and a short is ### sure. Doesn't even put a dent on the Glitch R. You can crowbar the thing all day long. #### We did find out where the HV arc was happening.... was between OUTPUT of parasitic suppressor globar clip.. and the 20- 17-15m 1/2" tubing tank coil... bad arc. When driven... the anode V rises to almost double [restored tank sine wave back feeds through plate block caps to anode.. adds to the existing dc HV.] Fix was to rotate the coil on it's axis a bit. ## Last time... the arcing was caused by LOOSE strap from C1 vac tune cap to 20-17-15 m tank coil. STRAP had flopped over a bit.... and arc occured between parasitic suppressor coil and this loose strap. Of course in both cases.. ALL the tank components are at chassis grnd... including tune/load caps/bandswitch/ both tank coils, etc.... due to the HB 45 uh 18 ga solenoid wound safety choke... wired between chassis and hot side of vac LOAD cap. [45 uh choke wound on 1" diam solid Teflon rod... bullet proof... also identical to the 45 uh RF choke used in the 2 x piece plate choke set up 135/180 uh + 45 uh] ### This safety RF choke HAS to be rugged... no place for your ARRL hand book 2.5 mh 30 ohm 36 ga.... pi wound assy. Those things will blow into a million pieces when you try and stuff 160 A through em. They also have more than a tendency to blow up.. with NO HV fuse.... and also with no glitch R.... well... use ur imagination... 8 kv / 1.4 ohms ESR from modern day lytics + plate choke = 5700 A Actually.. it's not that bad... since the DC resistance of any floozy RF safety choke will limit current... then the choke explodes. A 45 uh 18 ga safety choke is compact... and a snap to make. Drill + tap a 1/4-20 thread into the base... and it's easy to mount. 2 x Transverse brass threads terminate the 18 ga magnet wire. Later... Jim VE7RF R L Measures, AG6K, 805.386.3734 |
Re: Power factor correction for transformers
pentalab
--- In ham_amplifiers@..., "Robert B. Bonner"
<rbonner@...> wrote: automation (energy) company. We installed PFC caps on buildings all over the place. For the Super Big guns that are running 100 AMP primarys withthree phase power supplies doing PFC will just make the power to the primary smoother and your power company happier. I don't think it is worth the expense for correction caps. Either way I would install them on the amplifier not the building. ### On HV supplies with resonant choke filters.... they all have a better power factor... compared to a simple C input filter. When you increase the C in a C filter HC supply... the power factor gets WORSE. Sounds to me like this 90 deg lag is not a fixed thing... but vary's... depending on power factor itself... IE: .8 pf vs .9pf vs .98pf ### Since a simple C input filter has a WORSE PF than a resonant choke filter.... my electrician buddy is suggesting the huge C is responsible for the worsening pf.... and NOT the XL of either the pri/sec of the plate xfmr. If that's the case... Dahl is probably right, he should know. Dahl is telling me on a large C input filter, that you can't use PF correction caps on the pri of the plate xfmr. It just makes the PF worse still... and magnetizing current increases. Since the C filter on the output side is responsable for the lousy PF on a C input filter... probably what's needed is a choke.. or XL across the plate xfmr pri.... or perhaps in series with the plate cfmr pri ?? ### Even if it could be done... the load is not constant on the HV supply... it's nil [except for magnetizing current and bleeder] on RX.... and vary's on TX from ZSAC... to full bore. Any compensation would probably have to be relay switched out on RX... and optimized for an average load on TX... on ssb anyway. BOB DDtransformers and power supplies, and never found anything about using a cap for power factor correction. There's plenty about using a cap with an AC motor, but nothing about transformers. The Standard Handbook For Electrical Engineers only show adding them to motor circuits or circuits feeding motor loads. Nothing under the transformer section. ### That's what I suspected. I don't see any PFC caps on SW broadcast TX either... not at 1st glance anyway. None of them are using C input filters I believe.... might be wrong. With 3 phase HV... ripple is only 4.8 % b4 any filtering. A simple C input filter would reduce the ripple to zip. However a resonant choke would do the same thing.. and have a better power factor at the same time. For 24/7 operation.. and huge power... any savings would add up. use more iron in the core lowering its flux density. The more iron for the same amount of turns, the current drops. I researched magnetizing current in C-core Hipersil (or M-6) transformers some time back, and seen they had a good bit more magnetizing current than most EI cores using M-19 steel. The reason being is they run Hipersil from 15 to 17 kilogauss. M-19 and M-22 are ran from 14 to 10 kilogauss. Over 15 kilogauss in Hipersil, the current really shoots up. The way to cure this is to have a transformer wound with the same number of turns, but with a larger core area in either a C- core or an EI core. One would have to tell the winder to use a lower flux density of say 12 to 10 kilogauss using a C-core with Hipersil or M-6 for a low magnetizing current. M-19 for an EI core may be a better choice if available as it will be a good bit cheaper. The core loss isn't much greater than M-6 either. ### I'm gonna ask Dahl what kind of hypersil he uses. The 120 lb 10 kva hypersil pole pig I have has 1.9 A of magnetizing current at all times. The 253 lb Dahl hypersil has only 1.6 A of magnetizing current [it's a 3 A CCS sec = 15.5 kva CCS] I was expecting a LOT more magnetizing current from the 253 lb xfmr. [esp since it's double the weight of my pole pig]. The 1.6 x 240v = 384 Va of magnetizing va is small... compared to the 4.5 A int load you can pull off the sec. Still.. that's 384-va on RX all the time. ### BTW... it's 384 va... whether FWB/caps/bleeder connected... OR disconnected.. makes no difference.... even when sucking 100 w of bleeder diss. Ditto with pole pig supply. ### Dahl tells me the A-540 core he uses on all the 253 lb'ers is good for 20 KVA CCS. Once u get a sec over 4 kv... the CCS I rating drops from 4 A... down to 3 A. At 7.5 kv sec... it's then down to 2.5 A CCS. My xfmr [due to wire ga on sec] is rated at 15.5 kva..... however the core itself is good for 20 kva. later... Jim VE7RF Best, |
Re: Fried glitch R...... from an oversized HV fuse
Tony King - W4ZT
craxd wrote:
The boards are okay I guess but there is nothing special about the current trips. All they do is sense a voltage drop across a resistor with higher current and trigger an opto-couplers LED with it. This is turn will open a circuit by a relay or transistor circuit.What you say here is true, Will. Each individual circuit is simple. The major benefit to the boards is that you can buy one that has the circuits designed and ready to go. Not only that, but the trips are linked together to provide fault lines, both hard and soft, which can save more than just a little trouble fixing something. Ian and Paul both make good boards. My personal favorite is Paul's. He uses multi turn pots and the 26V supply is on board including the power transformer for it and the bias regulator circuit is there too. This not only eliminates the need for you to provide another supply but also provides the juice for the t/r and control relays as well. You can also implement as much or as little of it as you like. Another thing I seen in one board is that they sample a little of the screen or bias voltage and put that into a regulator to get the control voltage for a relay, etc. That was done to keep from having another coil on the transformer for low voltage. However, you need one anyhow for the antenna relay, and others.I haven't seen that. I design my own as to me any of the boards I've seen are a little over-kill and over complicated for my taste. The more components placed in any circuit raises the likelyhood of failure in the future expotentially. I can make just as good of a regulator circuit with a few transistors and zener diodes. This for either a series pass or shunt regulator.<snip> If you want cheap and easy, a simple design on proto board is fine for just the things you want. That's why I put together a simple bias board based on the same circuit commonly used with the TL431 reference to use as a retrofit bias board <>. Not everyone wants a complex system and not everyone appreciates the protection that you can have by using one of the control boards. It's just a personal choice and nice that we have those options today. My personal choice for home brew is to include the protection... Wouldn't build without it. For a retrofit, it usually isn't that practical or economical to do. Besides the trip circuits used on the control boards there have been several older commercial amps like the B&W PT2500 that included a grid trip circuit. It isn't all that difficult to build and use. I find the three lead regulators much more reliable than any series regulator built with a few transistors and zeners. They have over current protection and are so much simpler to use. Regards, Tony |
Re: AC HiPot tester question
pentalab
--- In ham_amplifiers@..., R L Measures <r@...> wrote:
over-...RICH SEZ.... A 20kV rated C to block 7000V DC sounds like isengineering since the actual AC potential across the blocker ####### The AC potential across the cap has nothing to do withminimal. it. fixed theglass/ceramic vac cap as a PLATE Blocker.... MIN V rating of V......FIXED vac cap has to be a MINIMUM of 3 X No load plate #### You don't have friends at Eimac... like me.RICH SEZ.... I did not read this in any Eimac literature,catalog on p.4 about DC operation state otherwise?other wise u get "whisker's" growing on the OFC plates on theRICH SEZ... So why does the statement I quoted in the Jennings RICH SEZ...and it does not make good sense ### sure it does. Apply continuous DC HV to a vac cap.,. and eventually... DCV rating.. due to whisker growth... DROPS...hence size the caps DC HV rating at least 3 x the plate supply's unloaded v to start with. That's what Jenning's sez... that's what Eimac sez... that's what 11m ops say... or else it's flash kablamo time ..... end of story. RICH SEZ...since the prima facie consideration for a DC blocker is the current rating at 29MHz - since at 10m, the DC blocker typically carries c. 90% of the tank's RF circulating current. #### "prima facie consideration" ? Are you OJ's lawyer too ? ### yes... 10m and above is the worst case scenario for a plate block cap.... that's what I have been saying all along. test V is the max WV when using DC + RF.The 11m ops also highly agree. TheRICH SEZ... Probably true since Jennings advises that 60% of the DC ### what ? Jenning's sez the max AC RF working V is 60% of the DC test V. They are asuming and also implying you have employed a plate block cap already. What they are refering too is using a vac cap as a C1/C2 tune/load cap... or using a vac cap to pad a tune/load cap. In any event... the AC voltage across a plate block cap is so low... u can ignore it.... UNLESS you insist on using really small value plate block caps... then you end up with high AC voltages across em.... as in plate current X Xc of plate block cap. ### for 10.5 kv dc no load... you want at least a 25-30 kv test v rated fixed vac cap. reactance. 176- ohms of XC and a RL of 176-ohms x 5 = 880-ohms or...RICH SEZ.... The rule of thumb is a 5 to one ratio for a couplingRICH SEZ... I do, Jim. Even 500pF is plenty for a DC blocker at1.8MHz (XC = 190- ohms) in typical amplifiers since RL is in the higher RL should be okay. ### No way. Where did u cook up this 5 to one ratio ??? Not in any of my engineering books. Any big metal tube operating with a 880 ohm plate load Z... is gonna be sucking loads of plate current. 4-5 A typ. 5 A x 176 ohms XC = 880 vac You just lost it right there! probably work okay if the Tune-C could tune it out.RICH SEZ... With a pair of 3-500Zs, RL is c. 2k, so 884-ohms would #### Now it gets even worse ! 5 A x 884 ohms = 4400 vac dropped across the plate block cap........ not to mention the 45-63A of RF flowing through it ..on 10m ! [using a 100 pf plate block cap + big metal tubes] RICH SEZ... > no #### It would vaporize.... that's why. in a 3x3 #### lemme see. With say 2.5 A of plate current at 5 kv under load... and on 29 mhz... current through the 100 pf plate block cap = 32 A. A HT-57 100 pf cap is only rated at 13.7 A @ 30 mhz [with 13.7 A, the 100 pf cap's temp is 55-65 deg C...149 deg F..... and well over 100+ deg C.. with 32 A flowing through it] Use multiple metal tubes on 10m or bigger single metal tubes with lots of anode to chassis C..... look out. ### with 32 A through a cap rated for 13.7 A = meltdown. [5.5 x more heat. 32/13.7= 2.34 2.34 squared = 5.5 more trbl] Don't gimme this nonsense about pulse tuning and SSB being a 15% duty cycle. The correct component here is 6 x 500 pf HT-57's... or 3-4 x 200pf HT-57's. I use 6 x 500 pf HT-57's.... then it will have low XC on 160m too. Later... Jim VE7RF ... |
Rich tells us how to Ram 300+ A through a 40 A breaker.
pentalab
--- In ham_amplifiers@..., R L Measures <r@...> wrote:
Ohm's Law. The calc. peak mains current was c. 300A. The measured result was 1200v- pk into 50-ohms on SSB. ### 1200 V pk equates to 14,396 watts pep output into a 50 ohm load....14,395.65 /.63 = 22,850 w dc input. Primary VA = 22,850 x 1.22 = 27,877 va 27,877 /240v = 116.155 A .... not including fil xfmr, blower etc. Peak current is aprx 375A with big wire and a big C filter... every 8.3 msecs. ### Rich... tell us how you take a steady state plate and grid current meter readings..... with out blowing ur under rated 40 A house breaker ???? IE: a dead cxr... for just 3-6 seconds... just long enough to measure grid/plate current + fil V, loaded plate V, etc. Forget the fil v/ plate v...... focus on just the plate + grid current. ### If u just pulse tune it...and talk...fine... I do too. Unless both ur plate/grid meter's are peak reading types.... I can't see how it's done. ### IMO.. the entire system should be configured to at least handle a 4-7 second dead cxr.... without blowing breakers, melting coax, frying tank coils etc. ### For a 8170/8171.... I'd use a 100A breaker... and a bare min of 2 ga wire... and considering the 300-400A peak current draw every 8.3 msec..... 3 x 000 CU is the real ticket.... regardless of length. ### BTW... what's the CCS rating of the SB-220's plate xfmr ??? I heard it was 1200 va. Now Rich has stated it's only 600Va. I'm sure the smaller SB-200 is 600 va CCS. ### Will a SB-220 stock... in good condition, on low plate V...be capable of delivering 600W CCS RTTY ??? If so... the plate xfmr would have to be a 1200 va unit. Later... Jim VE7RF R L Measures, AG6K, 805.386.3734 |
Re: Fried glitch R...... from an oversized HV fuse
pentalab
--- In ham_amplifiers@..., R L Measures <r@...> wrote:
the 250v-rated MOV's, Jim. ### I did. And the 250 v rating is for a 250 V max rms CCS condition. Depending on who makes a MOV.... clamp V is always way higher than that.... which is why old books always said to use twice the PIV needed for a FWB. These days it's triple the PIV needed [at least for commercial recifier assys]. ### MOV's are just a series of "grains" inside. The series grains will start to short out with successive hits from transients, spikes, surges, etc. The actual V rating of the MOV will slowly start to go down. That's why 130V rated MOV's are normally used. A 250 v rated Mov is cutting it too fine for folks whose line V can reach 247-250 V. A few too many hits on the MOV.. and it's continuous V rating will drop to the point where it will conduct.... and short out. UNLESS it's fused.... it's gonna burn up... or explode. Way too many house fires caused by MOV's as is. ### Check out Joslyn's website in the USA. They are the number one maker of commercial MOV assemblies for use in commercial / industrial environments. You won't see any 250 v rated MOV's used on any 240 V circuits. Their's come in several configs.... like 130/135 v MOV's from each hot leg to neutral.... and or... 275 V rated Movs across the 240 V line.... or 225 V rated Mov's from hot to neutral on a 208 3 phase setup. Their's are all fused as well as alarmed. The latest versions all have "event counter's" in em.. with time date stamps, etc. Some of the ones we use at work are 4" square and 1" thick...each... amd fused... and alarmed. ### Dahl sells MOV's. Why do you think his large bolt down ones are ALL 275 v rated ....and not 250 V rated ??? ### Rich... you just love to cut corner's and engineer stuff right to the peg... with zero leeway. Rauch does the same. The whole beauty of HB stuff is one can build it right the 1st time.... with no corners cut... and loads of headroom. Later.... Jim VE7RF R L Measures, AG6K, 805.386.3734 |
Re: Fried glitch R...... from an oversized HV fuse
craxd
The boards are okay I guess but there is nothing special about the
current trips. All they do is sense a voltage drop across a resistor with higher current and trigger an opto-couplers LED with it. This is turn will open a circuit by a relay or transistor circuit. Another thing I seen in one board is that they sample a little of the screen or bias voltage and put that into a regulator to get the control voltage for a relay, etc. That was done to keep from having another coil on the transformer for low voltage. However, you need one anyhow for the antenna relay, and others. I design my own as to me any of the boards I've seen are a little over-kill and over complicated for my taste. The more components placed in any circuit raises the likelyhood of failure in the future expotentially. I can make just as good of a regulator circuit with a few transistors and zener diodes. This for either a series pass or shunt regulator. Best, Will --- In ham_amplifiers@..., "pentalab" <jim.thomson@...> wrote: 24 vdc RELAY's... with contacts rated for 100-400A. AC contactor's"DM" means 'double make'.... IE: essentially each pole is two setsof contacts in series.... with an input lug... output lug... and ahandle the typ contactor solenoid coil. Most opto's have back emf3100- 9300 JOULES Everything else is just .."follow on energy".. fromused since the start up current is wicked on this stuff... as in 3-7"fail safe" on em so if they lose pwr... everything shuts off.... orusing 2 x 5 kv [5 kv AC...7kv dc] rated Buss sand filled fuses inlong HV fuse.... simply cuz they had a ton of 5 kv fuses... and had 10GM3SEK triode board installed on every amp you owned.... I'd haveone extra spare board put away... for a 'fast' replacement..if100 wis225on ssb] toAthen transfered to the 100 A breaker in the 240 v main 200panel.... which of course didn't blow open...... instead the KVAone ofoperate with NO hv fuse at all ?? nuts. withCCS with a 100 A slo breaker... vs lowly glitch R [woundnichrome wire no less] .... no contest.... glitch loses every |
Re: AC HiPot tester question
craxd
It sounds to me that Jennings wants things two different ways. First
they say don't momentarily test a vacuum cap with DC, but it's okay to put one in service as a DC blocking cap, de-rated or not. From everything I've ever read, the whisker problem is caused over time, not in one minute of use. A DC blocker cap could be in an amp for a lifetime. That's a good sales gimmick to sell hipots though. I've never seen that warning either by Comet, or by any of the Russian manufactured caps. If the cause is over the copper being too soft used for the plate cups, it ought to be changed to a hard copper or an alloy to stop it. I can see soft copper for the bellows, but not the plate cups. Thank God Rich and I didn't question the Jennings engineers on the other list as we would have been sent another e-mail by the unknown admin chastizing us for ever questioning these professionals with published papers, etc.... Best, Will --- In ham_amplifiers@..., R L Measures <r@...> wrote: 190- ohms) in typical amplifiers since RL is in the kilo-ohms range.expected11m ops don't need much C for 11m... 100-250 pf maxTom Rauch apparently knows a Ham who mistakenly used a 100pF DC output from 1.8 to 28 MHz. Sometime later, when a friend wasbeing shown the amplifier, he noticed that there were only twp zerosafter the 1 on the blocker cap. When a 1000pF cap was substituted forthe 100pF cap, the output did not increase although the tuning changed |
Re: Fried glitch R...... from an oversized HV fuse
Tony King - W4ZT
pentalab wrote:
--- In ham_amplifiers@..., Tony King - W4ZT <w4zt- 060920@...> wrote:Thanks, wasn't sure which "big" ones you used.Which MOV's do you use and where do you get them?### From Mouser... Digi key has em as well... aprx 2" tall x 1/2" thick x 2.75" wide base. Those are the 130 v units. The closest ### ACROSS poles of contactor's, you want 250-275 V rated Movs...Agreed. ## I install the 130 v rated Mov's between each hot leg and grnd.... right at the plate xfmr primary.... and 2 x 275 v rated mov's, in parallel, directly across the plate xfmr primary.We are in agreement! I believe in the protection circuits too... there's more to discuss about these things... see below. True... but if the fuse doesn't open... or if it does, and the faultof### seems to me the 2 x triode boards wouldn't handle 3-4 Afornormal anode current... but might be modified ?Look at Paul's board... you can set it up with any external shuntdetecting a fault. Use the board to control any kind of contactoryou have. doesn't clear, it's best to take the HV supply off line. The control of the contactors will be slower than the fuse and should not see the huge load as it opens... that may be a matter of timing. ### Watch the relay/contactor... when opening it off... while sucking 100+ A key down ! Imagine this again.... but with 2-4 x more current during a fault condition. Then toss in a high value C filter for fun. Peak current on the 240 V line every 8.3 msecs is 4-6 x normal operating current as is... never mind a fault condition.yup... see above. Simple is good (KISS) but not best when expensive tubes are at risk.have been an issue.### I just wanted to keep it simple. Any electronic protection would have to be in addition to properly sized HV fuses and primary breakers.And if your friend had used a correctly sized fuse, it wouldn't #### Correct. Which was the whole point of the title in the post. They also ran out of 750 Ma fast grid fuses one night.. and stuffed in some 3 A fuses ! If they had lost HV.... the grid current would peg when driven [normal]. The 750 ma grid fuse woulda blown asap... and input swr rises to infinity... and IPA/Xcvr shut down. With a 3 A grid fuse, they woulda damaged the grid.And that is the point of using the triode control board. Note that it will fault the amp off line, breaking the key line, if you exceed a preset your grid cutoff current. There is lots to be said for not transmitting into the amp with no HV on it. So true... and even if the electronic protections are there, if one chooses to defeat them they will not help.Well, this thread started with your description of a failure caused### agreed. I have no control over my buddy's amp. I can just make a suggestion...that's it. I think once they blow stuff up from oversizing.. that they probably won't do it again. A few spare correct size fuses is cheap insurance. If a fuse blows..... don't put in a bigger one... find the reason it blew ! Thanks Jim, Tony W4ZT |
Re: AC HiPot tester question
On Nov 19, 2006, at 6:49 AM, pentalab wrote:
--- In ham_amplifiers@..., R L Measures <r@...> wrote:I did not read this in any Eimac literature, and it does not make good sense since the prima facie consideration for a DC blocker is the current rating at 29MHz - since at 10m, the DC blocker typically carries c. 90% of the tank's RF circulating current.wrote: The 11m ops also highly agree. TheProbably true since Jennings advises that 60% of the DC test V is the max WV when using DC + RF. ...The rule of thumb is a 5 to one ratio for a coupling reactance. 176- ohms of XC and a RL of 176-ohms x 5 = 880-ohms or higher RL should be okayRICH SEZ... I do, Jim. Even 500pF is plenty for a DC blocker at1.8MHz (XC = 190- ohms) in typical amplifiers since RL is in the IF the fixed VAC capAt 7500v with 1500v on the screen, an 8171 has a RL of c. 1000-ohms. Smells kinda like bacon. With a pair of 3-500Zs, RL is c. 2k, so 884-ohms would probably work okay if the Tune-C could tune it out. no ### A 3x6 has a 1100 ohm plate load Z.. when run full bore.Amen, Jim esp with metal tubes.. with lotsa strayWhy would the capacitor dissipate heat? ... R L Measures, AG6K, 805.386.3734 r@..., rlm@..., www.somis.org |
Re: Fried glitch R...... from an oversized HV fuse
On Nov 19, 2006, at 7:32 AM, pentalab wrote:
--- In ham_amplifiers@..., Tony King - W4ZT <w4zt-Perhaps it might be a good idea to read the specs on the 250v-rated MOV's, Jim. R L Measures, AG6K, 805.386.3734 r@..., rlm@..., www.somis.org |