gordon@boulder.Colorado.EDU (GORDON ALLEN R) (11/06/90)
I am involved in a project using the output of a small DC hydroelectric plant and a couple of solar panels to power a residence in rural New Mexico. We currently have an inverter which produces a modified sine wave output, ie., positive and negative pulses to run the household appliances. Since the power plant will be expanded in the future along with the inverter, we are con- sidering the kind of inverter to use. We will have electronic equipment, such as computers, faxes, VCR, along with the ususal household appliances on this system. Does anyone know of any long term effects of using such an inverter, rather one which produces a real sine wave, such as might be obtained with a synchro- nous one, on these kind of electronics? How sensitive are computers etc to pulse input rather than sine wave? Would power line conditioners be required? Thanks, Allen Gordon
jgd@rsiatl.UUCP (John G. DeArmond) (11/06/90)
gordon@boulder.Colorado.EDU (GORDON ALLEN R) writes: >Does anyone know of any long term effects of using such an inverter, rather >one which produces a real sine wave, such as might be obtained with a synchro- >nous one, on these kind of electronics? How sensitive are computers etc to >pulse input rather than sine wave? Would power line conditioners be required? See my previous posting on the subject for details. I have a homemade 1 kw square wave UPS that runs this system and its peripherals. I've also experimented with running other devices one might find around the house. The only thing I've found that absolutely refused to run on square wave power is my microwave oven. The unit would fire up and run but it would not heat. The reason is that the magnetron depends on the peak value of the line voltage for its drive. This could be easily rectified with an inverter adjusted to a higher average voltage. I think the concept of an inverter for each load center is an extremely viable option. No line conditioning is needed. John -- John De Armond, WD4OQC | "The truly ignorant in our society are those people Radiation Systems, Inc. | who would throw away the parts of the Constitution Atlanta, Ga | they find inconvenient." -me Defend the 2nd {emory,uunet}!rsiatl!jgd| with the same fervor as you do the 1st.
mcmahan@netcom.UUCP (Dave Mc Mahan) (11/06/90)
In a previous article, gordon@spot.Colorado.EDU (GORDON ALLEN R) writes: >I am involved in a project using the output of a small DC hydroelectric plant >and a couple of solar panels to power a residence in rural New Mexico. We >currently have an inverter which produces a modified sine wave output, ie., >positive and negative pulses to run the household appliances. Since the power >plant will be expanded in the future along with the inverter, we are con- >sidering the kind of inverter to use. We will have electronic equipment, such >as computers, faxes, VCR, along with the ususal household appliances on this >system. > >Does anyone know of any long term effects of using such an inverter, rather >one which produces a real sine wave, such as might be obtained with a synchro- >nous one, on these kind of electronics? How sensitive are computers etc to >pulse input rather than sine wave? Would power line conditioners be required? I have used such inverters with IBM-PC/XT's, and have had good luck with that. Note that I'm no expert, but it worked fine for us. I have been told that a switching power supply (as used within the PC) is very tolerant to such sources of power. I would think that a fax machine also uses some form of a small switching power supply and would be ok to use. I have no clue about VCR's and other items. Since they are created for the mass market and are made as low-cost as possible, you might have some problems. Is it possible for you to find devices that will accept DC? They would probably cost more but you could feel pretty confident that they will continue to work for years. >Allen Gordon -dave -- Dave McMahan mcmahan@netcom.uucp {apple,amdahl,claris}!netcom!mcmahan
lairdkb@mentor.cc.purdue.edu (Kyler Laird) (11/07/90)
This week's PC Magazine says that computers can take all sorts of AC power without problems. This was in the context of UPS's. --kyler
karn@envy.bellcore.com (Phil Karn) (11/07/90)
In article <29237@boulder.Colorado.EDU>, gordon@boulder.Colorado.EDU (GORDON ALLEN R) writes: |> Does anyone know of any long term effects of using such an inverter, rather |> one which produces a real sine wave... "Modified sine wave" inverters produce a 50% duty cycle square wave with the same peak and RMS voltage as a sine wave. The output voltage follows the sequence 0, +170V, 0, -170V, ... (170 is sqrt(2)*120, the peak voltage of a 120 V RMS sine wave). Computers and other devices with switching power supplies don't care at all. They directly rectify and filter the AC power line, so as long as the peak waveform voltage is the same (and it is) they'll work fine. Most consumer electronic devices with power transformers also feed rectifier/capacitor filters, so the modified sine waveform will have little effect on them too. There is one exception: line-driven clocks (such as the one in my VCR) will often run at the wrong speed (usually twice as fast). My guess is that they're looking for zero crossings in the AC waveform, and the 4 edges per cycle of the "modified sine wave" fool the zero crossing detectors. Another unit I had problems with is my old Pioneer SX-780 receiver. It has a speaker protection relay with a circuit that, among other things, watches for AC power failure by sampling the power transformer output before the rectifier. This circuit cuts off the speakers before the DC from the power supply begins to collapse, avoiding the turn-off thump that would otherwise occur. This circuit is also fooled by the "modified sine waveform", causing the relay to click on and off continuously (no permanent damage to the unit, though). I've heard claims that conventional core-coil flourescent ballasts will not last as long on modified sine waveform inverters, but I have no direct experience with that. In any event, electronic ballasts are lighter, more efficient and not that more expensive so I buy them in all my compact flourescents. Phil
karn@envy.bellcore.com (Phil Karn) (11/07/90)
By the way, those interested in independent power systems (solar, hydro, etc, combined with batteries and inverters) really ought to check out the catalogs and sourcebooks from alternative energy companies such as Real Goods and Backwoods Solar. Granted, you'll have to tolerate a lot of environmentalist polemics, but they *do* have useful, practical experience in engineering real, working systems. Now if they could only get some of their other numbers right, like the total amount of energy the sun radiates (Real Goods' figure is off by 1e9) and do a more balanced comparison between solar and fossil fuel power that takes into account the energy required to produce solar panels and the environmental costs of lead-acid batteries... Phil
gaarder@batcomputer.tn.cornell.edu (Steve Gaarder) (11/08/90)
In article <29237@boulder.Colorado.EDU> gordon@spot.Colorado.EDU (GORDON ALLEN R) writes: >We currently have an inverter which produces a modified sine wave output... >Does anyone know of any long term effects of using such an inverter, rather >one which produces a real sine wave...? Most electronics should take it ok. The stuff you have to worry about is that which puts a large capacitive or inductive load on the unit. Motors and fluorescent lights with non-electronic ballasts fall in this category. Effects I would watch out for are overheating and shortened lamp or ballast life. Also, check the inverter - some should not be used with a load that is too reactive. With motors, there is also the starting current to factor in - it can be a lot more than the running current. Steve Gaarder gaarder@batcomputer.tn.cornell.edu