I'm not sure of what you are asking. Line current on genset is not going to be any less than on normal utility power. Line is line no matter what. I sure don't understand your reference to metric? Power is power. If perhaps you had a large commercial site, this would have to be considered. However, it would take conversion of a number of power supplies to become a real significant issue. Lighting, heating, air-conditioning, and power to "other equipment" far outweigh this. ----- Original Message ----- From: "Jay Urish" <[EMAIL PROTECTED]> To: <[email protected]> Sent: Monday, January 15, 2007 1:48 PM Subject: Re: [Repeater-Builder] minor formula typo in formula switching power supplies
> How about the other metric? Load on th AC Mains should the grid drop and > everything switches over to Genset. > > Does the switcher pull less AC as well? With DC load and without? > > WYSA wrote: >> >> >> Hi Dave, >> >> I read with interest your comments. Lets do some math to see if your >> decades long pay back is correct. >> >> I agree with your observation about efficiency being the only real >> difference between the two types of supplies. >> So taking that input, lets see what the numbers say. >> >> Typical Setup (numbers rounded to make the math easy): >> >> DC Load: 14 vdc at 30 amps >> Usage: 10 hours per day, 365 days per year >> Electricity cost: 10 cents per KHw >> >> Setup 1: >> Linear supply (ASTRON RM35 for example) >> >> Looking at the schematic, the output of the transformer (into the linear >> regulator circuit) is 25 volts at full load, lets say 30 amps. >> The load power is 14 volts times 30 amps or 420 watts. >> The power into the linear regulator is 25 volts times 30 amps or 750 >> watts. Linear regulators dissipate the difference as heat... >> This gives an efficiency of 56% (420/750 *100) >> Lets say the supply needs 750 watts to supply 420 watts, ignoring mag >> core losses, phase, etc. >> The total yearly run time is about 3650 hours (10*365). >> Total KWh is 750*3650/1000 = 2,737 KWh per year >> Total cost is about $273 per year (10 cents * 2737 KWH). >> >> >> Setup 2: >> Switching power supply (General type) >> >> Load power is again 420 watts. >> Typical efficiency is 80%. There are higher efficiency power supplies, >> but lets use 80% for now. >> This gives an input power of 525 watts (420 / 0.8) >> Total yearly run time is again 3650 hours. >> Total KWh is 525*3650/1000 = 1,916 KWH per year >> Total cost is about $191 per year. >> >> >> The switcher will save you $82 per year in lower electric costs. This >> savings is for each power supply in use, given the duty cycle above. Of >> course, the lower your current requirements or lower duty cycle, the >> less you save in real dollars per year. However, I do not see any >> chance of a decades long pay back... I'll take the $82 per year savings >> and the lower heat load in the cabinet any time. The one exception >> might be if the room also houses or uses LF of HF communications. I'd >> be more careful in the situation. Otherwise, why not??? >> >> Sometimes the devil is in the details. I've been a BSEE for 23 years >> now and the smallest details can get ya. One comment about my analysis, >> I have not taken into account power factor correction or phase angle >> issues. Most modern switchers now come with power factor correction in >> the AC input side. The analysis was meant to be simplistic to give the >> reader an idea on how much efficiencies can affect situations. YMMV and >> other such sayings... >> >> Hope this helps someone, >> Marc >> >> >> >> >> -----Original Message----- >> *From:* [email protected] >> [mailto:[EMAIL PROTECTED] *On Behalf Of *DaveH >> *Sent:* Monday, January 15, 2007 8:41 AM >> *To:* [email protected] >> *Subject:* [Repeater-Builder] minor formula typo in formula >> switching power supplies >> >> A minor formula exists in the P=EI formula in the original message. >> The >> corrected version is below. To many annoying phone calls! Sorry >> about that! >> Dave >> ----- Original Message ----- >> From: "DaveH" <[EMAIL PROTECTED] <mailto:w2drh%40hvc.rr.com>> >> To: <[email protected] >> <mailto:Repeater-Builder%40yahoogroups.com>> >> Sent: Sunday, January 14, 2007 6:27 PM >> Subject: Re: [Repeater-Builder] Re: Switching Power Supply vs. >> Astron Etc. >> >> > Erick, >> > I agree with you! The only difference will be any increased >> > efficiencies in the switcher over the mag and that will be small. >> I have >> > had >> > a Master Electrical License for 38 years. A physical law of >> science says >> > that 746 watts equal 1 horsepower> There is no deviation from that >> > scientific fact. In addition, if the equipment that is powered by >> the >> > astron, draws 30 amps, it's going to draw 30 amps on the >> switcher. THAT >> > CANNOT CHANGE> The power supply, both switcher and mag type, will >> draw >> > the >> > required line current that is demanded by that load. Ohm's law >> says P=EI >> > (power ((wattage)) = E((voltage)) multiplied by the amperage >> ((I)). If 30 >> > amps >> > are required at 13.8 volts the resultant power consumed will >> REMAIN THE >> > SAME POWERED BY THE MAG OR SWITCHER SUPPLY. Since this physical >> law cannot >> > change, then the efficiency differences between the two types of >> supply >> > will >> > be the ONLY POSSIBLE DECREASE IN CONSUMED ELECTRICITY. >> > Since efficiency is the ONLY POSSIBLE GAIN and the switcher cannot >> > generate electricity and there is no perpetual motion, needed >> magnetizing >> > current decrease and possible utility current power factor >> improvements >> > are >> > the ONLY POSSIBLE IMPROVEMENTS THAT CAN OCCUR. If you consider >> these >> > facts, >> > you will instantly see that utility cost reductions will be >> minimal at >> > best. >> > Electrical company power charges are calculated in KWH (kilowatt >> hours). >> > That is calculated by the formula KHW (killer what hours ((hi hi)) >> = >> > wattage load (both apparent and actual) multiplied by the time >> used and >> > divided by one thousand. Since the inefficiencies are these SMALL >> > differences, any real electrical cost savings will be in pennies >> on the >> > monthly bill and that is if the utility apparent wattage is in >> line with >> > actual use (power factor corrected). >> > As you can see, the only real advantage to the switching supplies >> are >> > mostly physical. By the way. Accurately measuring these electrical >> > differences with metering equipment can get quite complicated >> since ac >> > power factor is involved. To correctly measure this you need to >> correct >> > power factor by using correction capacitors. That is why utility >> meters >> > have >> > a designed and approved accuracy of 1.5 to 2 percent (this is >> national >> > standard and regulation required). If anyone believes they are >> going to >> > save >> > any substantial amount of money by converting to switchers, they >> are going >> > to be rudely awakened. It would take decades to recoup the cost >> of such >> > equipment replacements based upon utility savings. >> > One last myth left to clear up. A power supply connected to ac >> current >> > and left turned on 24/7/365 is the way to insure increased >> equipment >> > longevity. I have heard many people say they must "turn their >> power supply >> > off when equipment is not being used to save electricity." >> NOTHING COULD >> > BE >> > MORE ERRONEOUS. The ONLY electricity being consumed when the load >> is >> > switched off, is magnetizing current and voltage correction >> current from >> > leakage etc. >> > Since this is relatively minute, those "significant savings" are >> > nonexistent. Once again we speak of pennies. If you consider the >> stress >> > caused by switching the power supply on and off many times, in >> the end you >> > loose. Life expectancy is decreased by in rush, each time the unit >> is >> > re-energized. I have had Astron mag. supplies functioning for >> DECADES with >> > no failure. As long as the input is protected by GOOD electronic >> spike >> > suppression, failure is mostly limited to age or abuse (possible >> load >> > shorts). >> > I can only hope this helps clear up confusion and to eliminate >> > conjecture regarding these subjects. >> > >> > David R. Henry LME >> > >> > ----- Original Message ----- >> > From: "Eric Lemmon" <[EMAIL PROTECTED] <mailto:wb6fly%40arrl.net>> >> > To: <[email protected] >> <mailto:Repeater-Builder%40yahoogroups.com>> >> > Sent: Sunday, January 14, 2007 3:07 PM >> > Subject: RE: [Repeater-Builder] Re: Switching Power Supply vs. >> Astron Etc. >> > >> > >> >> Larry, >> >> >> >> You have a golden opportunity to provide an extremely valuable >> service to >> >> the radio community! If you can obtain the use of a wattmeter, >> you can >> >> make >> >> a comparison between the two power supplies. One such meter is >> the "KILL >> >> A >> >> WATT" meter that is sold under several brand names. It is >> inexpensive, >> >> and >> >> accurate enough for our purposes. >> >> >> >> Try measuring the power- both real and apparent- drawn by the >> same >> >> equipment >> >> while operating on the TPN1110B supply, and again while >> operating on the >> >> TPN1151A supply. Make a note of all parameters in both the idle >> state >> >> and >> >> while transmitting. I'll be surprised if the energy used by the >> switcher >> >> is >> >> not much less than the ferro-resonant unit. >> >> >> >> Keep in mind that the utility charges its customers for the >> consumption >> >> of >> >> real power in watts over time, in kWh. In an AC circuit, the >> independent >> >> measurement of volts and amperes does not equal watts unless the >> load is >> >> resistive, which is definitely not the case with a power supply. >> >> Therefore, >> >> the measurement of current drawn by each power supply is >> meaningless, >> >> since >> >> it is not in phase with the voltage. The product of >> unsynchronized >> >> measurements of volts and amps in an AC circuit is VA, not >> watts, and >> >> will >> >> differ from watts depending upon the power factor. But, I >> digress... >> >> >> >> Just the watts consumed by each power supply in standby and >> transmit >> >> modes >> >> will be important to know. Once you see the difference, you may >> be >> >> inclined >> >> to stick with the switch-mode power supply- especially if you >> are paying >> >> for >> >> power. >> >> >> >> 73, Eric Lemmon WB6FLY >> >> >> >> >> >> -----Original Message----- >> >> From: [email protected] >> <mailto:Repeater-Builder%40yahoogroups.com> >> >> [mailto:[email protected] >> <mailto:Repeater-Builder%40yahoogroups.com>] On Behalf Of >> >> [EMAIL PROTECTED] >> <mailto:larryjspammenot%40teleport.com> >> >> Sent: Sunday, January 14, 2007 11:28 AM >> >> To: [email protected] >> <mailto:Repeater-Builder%40yahoogroups.com> >> >> Subject: Re: [Repeater-Builder] Re: Switching Power Supply vs. >> Astron >> >> Etc. >> >> >> >> Would I gain any advantage by changing out my Motorola MICOR >> Repeater >> >> TPN1110B supplies (the ones with the constant-voltage >> transformer) to the >> >> TPN1151A Switching power supply? I have a few spares of each >> type, but >> >> most >> >> of my MICOR Repeaters came with the 1110B supply installed. >> >> >> >> I don't know why there were two types of supplies offered with >> the MICOR >> >> Repeater/Base Station radios. The switching supplies seem to be >> very >> >> quiet >> >> (even around an HF radio), as far as I have been able to >> determine. Some >> >> of >> >> the MICOR service manuals have sections for both supplies, to >> cover the >> >> particular unit that was supplied with the user's station. >> >> >> >> LJ >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> Yahoo! Groups Links >> >> >> >> >> >> >> >> >> > >> > >> > >> > >> > >> > >> > >> > Yahoo! Groups Links >> > >> > >> > >> > >> >> > > -- > Jay Urish W5GM > ARRL Life Member Denton County ARRL VEC > N5ERS VP/Trustee > > Monitoring 444.850 PL-88.5 > > > > > > > > Yahoo! Groups Links > > > >
