While we are talking about power, can anyone tell me why much of the world uses 50hz? It seems to me 60hz (or higher) is more efficient to transform or rectify. Also 60 can be divided by a lot of numbers, seems it would be easier to wind a generator...John
Utility frequency - Wikipedia, the free encyclopedia
I wish we all had 400Hz...and three phase everywhere 😀
Cooling your amp projects: Knock hole in exterior wall and put welding fan/blower in housing on the outside. Suck hot air out of amp to outside through suitable ducting, leaving blower noise out as well.
4CX250B for audio amp: Running these without *EFFECTIVE* screen grid RF bypass directly to cathode plus serious shielding is instant VHF oscillator. Floating screens at some audio voltage with dinky 100 ohm suppression resistors is a bit funny. 😀 Check Eimac SK620 air system socket, it has the cap built into the screen grid connector. I wouldn't want the amp for the fan noise either. Those tubes need serious air pressure to run at full ratings.
Radio amateurs usually run 4CX250Bs and similar tubes with at least 30dB of input/output isolation across all RF frequencies, DC to daylight, and add grid dampening (aka. dummy load) as well to ensure stability. g1 to anode gain is in excess of 20dB at up to 500MHz, and it is kinda hard to get these tubes stable without proper isolation.
Attached photo of example PSU with single core, triple phase transformer mentioned earlier. Intended for amp with a tube with handles. Not audio though...
Tubelab: 7289 aka. 2C39BA on military steroids is not a good audio candidate, unless you want to water cool it. They are hard to cool efficiently using only air, even though they are specified for 100W dissipation. I wouldn't want an air cooled class A amp with those running near that limit. No idea if they are linear enough, just talking about cooling here.
Edit: Forgot to mention: 4CX250B and similar external anode tubes regularly flash over internally between anode and (screen) grid, whichever is closest to the anode. This is normal and expected. These flashovers need to be dealt with by combining overvoltage protection of the screen grid by discharging the energy to ground without destroying the screen grid bypass capacitor (where the grid in question isn't directly grounded).
Also, there is a limit to how much energy the PSU smoothing capacitance is allowed to dump into the tube during a flashover. Forget the limit in Joule for the small tubes, but the figure is somewhere in the Eimac literature. This is usually dealt with by simply placing a suitably (physically) large high wattage resistor in the B+ lead, something like 50 or 100 ohm/100W usually suffices. When the flash over happens, it appears as a dead short. The resistor now has the highest resistance in the circuit to ground (since you have overvoltage protection of the screen), and the full B+ happens across the resistor, leaving little energy for the internal spark. Thus it extinguish and normal service resumes. The resistor then needs to be able to hold off the full B+ for a short moment, thus the requirement for it to be physically large. It is usually chosen to be something like a glazed porcelain resistor or one made from a similar material.
- Frank.
4CX250B for audio amp: Running these without *EFFECTIVE* screen grid RF bypass directly to cathode plus serious shielding is instant VHF oscillator. Floating screens at some audio voltage with dinky 100 ohm suppression resistors is a bit funny. 😀 Check Eimac SK620 air system socket, it has the cap built into the screen grid connector. I wouldn't want the amp for the fan noise either. Those tubes need serious air pressure to run at full ratings.
Radio amateurs usually run 4CX250Bs and similar tubes with at least 30dB of input/output isolation across all RF frequencies, DC to daylight, and add grid dampening (aka. dummy load) as well to ensure stability. g1 to anode gain is in excess of 20dB at up to 500MHz, and it is kinda hard to get these tubes stable without proper isolation.
Attached photo of example PSU with single core, triple phase transformer mentioned earlier. Intended for amp with a tube with handles. Not audio though...
Tubelab: 7289 aka. 2C39BA on military steroids is not a good audio candidate, unless you want to water cool it. They are hard to cool efficiently using only air, even though they are specified for 100W dissipation. I wouldn't want an air cooled class A amp with those running near that limit. No idea if they are linear enough, just talking about cooling here.
Edit: Forgot to mention: 4CX250B and similar external anode tubes regularly flash over internally between anode and (screen) grid, whichever is closest to the anode. This is normal and expected. These flashovers need to be dealt with by combining overvoltage protection of the screen grid by discharging the energy to ground without destroying the screen grid bypass capacitor (where the grid in question isn't directly grounded).
Also, there is a limit to how much energy the PSU smoothing capacitance is allowed to dump into the tube during a flashover. Forget the limit in Joule for the small tubes, but the figure is somewhere in the Eimac literature. This is usually dealt with by simply placing a suitably (physically) large high wattage resistor in the B+ lead, something like 50 or 100 ohm/100W usually suffices. When the flash over happens, it appears as a dead short. The resistor now has the highest resistance in the circuit to ground (since you have overvoltage protection of the screen), and the full B+ happens across the resistor, leaving little energy for the internal spark. Thus it extinguish and normal service resumes. The resistor then needs to be able to hold off the full B+ for a short moment, thus the requirement for it to be physically large. It is usually chosen to be something like a glazed porcelain resistor or one made from a similar material.
- Frank.
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More phases is fine for a motor, but a PITA for power factor correcting other loads.
Especially loads that would abuse so many phases to conduct only at the peaks.
Especially loads that would abuse so many phases to conduct only at the peaks.
For a given dc load current the rectifier current pulses are spread out over 3 times the effective area, individual rectifiers deliver approximately 1/3 the current as is the case with a single phase rectifier, and the peak currents scale the same way. You also get much less ripple voltage for a given input capacitance and load current. (Ripple frequency is also 3 times the single phase ripple frequency which makes it easier to filter. Smaller chokes and caps are possible for a given ripple voltage) I'd kill for 3 phase here and would run my bigger amps off of it in a heart beat.
Kitchen appliances above a certain size (ranges, ovens, etc.) in some Western European countries (like Belgium, Holland, and Germany) are sometimes designed to run off of 3 phase power. Living in Brussels we had 3 phase outlets in our kitchen which as a teenager I though was very odd.
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Make that 'always' these days. All ovens and such runs off 3 phase AC in most European kitchens. I find anything else odd, as it has always (from my perspective) been this way to me. 😉
I didn't want to make a blanket statement 😛 because somewhere that is undoubtedly not the case, it wasn't in Italy when I lived there, but a lot of water has since passed under that bridge.
I'm pretty sure my Mom's custom kitchen in the place they finally bought in Brussels had 3 phase for the wall oven and cook top.. It really makes sense to me on a number of levels.
We have 3 phase power distribution in our neighborhood at 22kV, but the power into all single family residences is single phase center tapped 240V.. I have a friend in another city who owns a very large house and outbuilding and he does have 3 phase power, but it is a rarity even where it technically could be made available.
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Well, I believe it has been a few years since the EU and neighbors standardized the electric grid and voltages, so I'm fairly certain the majority of European households has triple phase AC these days. I won't quite stick my neck out and say 'all' though... 😉
Come to think of it, I do wonder if the original argument for doing this still holds? I believe the original idea was to even out the load on the three phases, resulting in better utilization of transmission wires, plus making load distribution easier for the power plants.
There are other fun and entertaining differences in electricity standards between countries around the world, which may not really mean a lot in practice. For instance Danes has something about trees, so we tend to plant them everywhere we get a chance.
Unfortunately we also have regular autumn and winter storms. Add these ingredients, and an electricity grid carried by wires hanging from masts and poles isn't such a hot idea. So something like 25 years ago it was decided to literally bury *all* of the electric grid in Denmark, down to and including the connection to each individual consumer. Only exceptions are the very high voltage transmission lines, like 400KV, and even some of those are going underground as time passes.
This job was completed some years ago, but it got done. Makes the cleanup after a storm so much easier. Strange but true. 😀
Come to think of it, I do wonder if the original argument for doing this still holds? I believe the original idea was to even out the load on the three phases, resulting in better utilization of transmission wires, plus making load distribution easier for the power plants.
There are other fun and entertaining differences in electricity standards between countries around the world, which may not really mean a lot in practice. For instance Danes has something about trees, so we tend to plant them everywhere we get a chance.
Unfortunately we also have regular autumn and winter storms. Add these ingredients, and an electricity grid carried by wires hanging from masts and poles isn't such a hot idea. So something like 25 years ago it was decided to literally bury *all* of the electric grid in Denmark, down to and including the connection to each individual consumer. Only exceptions are the very high voltage transmission lines, like 400KV, and even some of those are going underground as time passes.
This job was completed some years ago, but it got done. Makes the cleanup after a storm so much easier. Strange but true. 😀
Power factor has nothing to do with ease of removing ripple.
Its about narrow conduction angle problem seen by the utility.
What seems a convenience to you becomes a hassle for them.
I understand that, I believe it is the case that the effective conduction angle with 3 phase rectification (I'm specifically talking about the six diode Graetz bridge) is somewhat more benign than is the case for single phase for a given input capacitance and output load current. Star configuration provides much lower ripple voltage at the expense of much worse power factor than the Graetz. Better power factors in general can be achieved with choke input. Perhaps I am mistaken, but this was my understanding. It is clearly more efficient when large load currents are being dealt with hence its use with heavy loads. (And kitchen appliances in the EU.)
What would you do instead? Obviously when you look at the efficiency of single phase in high power applications it is clear that the 3 phase has lots of advantages in distribution.
Very large 3 phase switchers these days generally at least have the option to specify PF correction when ordered. The EU actually has quite specific PF requirements for mains connected devices, expressly so that the utility does not have to cope with extreme power factors, whether or not these are currently enforced I don't know.
Even here industrial users here are often penalized by the utility for extreme power factors to encourage them to use PF correction. (According to the owner of a small machine shop I know locally.)
References:
http://web.ing.puc.cl/~power/paperspdf/dixon/21.pdf
Various bridges and their performance considerations, see section 12-10 for graetz bridge and commutated variants, see section 12-51 for a 3 phase active power filter.
All I am really trying to say is there are means to address all of these issues at the load end of things, and legislation will probably make it mandatory if it is not already so.
They are for industrial scale customers, at least here in Denmark, and fairly brutally: The large customers get to pay for the non-PF corrected load, not in-phase power delivered. Thus industrial sized customers tend to build suitable PF correction facilities on their own accord. 🙂
The power companies couldn't care less about the odd domestic user running a KW level rectified PSU without PF correction, and mass produced electric equipment is taken care of at the approval/manufacturing stage.
AVE...
Here there are higher prices for electricity for industrial customers, who have no PF correction and many capacitive or inductive loads. Electric stoves and ovens rated above 2.5kW have to run on separate 1-phase power line, above 3.5kW have to be connected to 3-phase line, for which consumer must pay the equivalent of 5-10 typical monthly salaries...
Also domestic consumers don't have to care about PFC, because it won't be traced back to the specific consumers, and the company has it's own facilities to take care of the PF correction. And you can always make active PFC and then use SMPS. However it would be complicated and expensive. I think I would try to design this... 😀
Here there are higher prices for electricity for industrial customers, who have no PF correction and many capacitive or inductive loads. Electric stoves and ovens rated above 2.5kW have to run on separate 1-phase power line, above 3.5kW have to be connected to 3-phase line, for which consumer must pay the equivalent of 5-10 typical monthly salaries...
Also domestic consumers don't have to care about PFC, because it won't be traced back to the specific consumers, and the company has it's own facilities to take care of the PF correction. And you can always make active PFC and then use SMPS. However it would be complicated and expensive. I think I would try to design this... 😀
I feel lucky living in the UK then...
A standard mains socket we can pull 3250 watts from ... and I have an 11KW electric shower in my house, and that's single phase.
It's rare, but not unheard of to have 3 phase in a domestic property. All domestic appliances are single phase.
To balance phases, streets are wired so that every third house is on the same phase. This only tends to occur in housing estates built 1950's and on ...
A standard mains socket we can pull 3250 watts from ... and I have an 11KW electric shower in my house, and that's single phase.
It's rare, but not unheard of to have 3 phase in a domestic property. All domestic appliances are single phase.
To balance phases, streets are wired so that every third house is on the same phase. This only tends to occur in housing estates built 1950's and on ...
AVE...
I have currently 3 fuses, each rated 20A/230V. One for lights. one for wall sockets, one for washing machine and fridge. This I had to add because when I ran both fridge and washing machine in the same time from socket, it blew fuses. Outside my home there is a main fuse, rated 50A, I believe. So, I can take up to 16kW for whole household...
I have currently 3 fuses, each rated 20A/230V. One for lights. one for wall sockets, one for washing machine and fridge. This I had to add because when I ran both fridge and washing machine in the same time from socket, it blew fuses. Outside my home there is a main fuse, rated 50A, I believe. So, I can take up to 16kW for whole household...
Here, every third street is on the same phase. The 3 phase lines go down the center of the neighborhood, but each street gets only one phase. Houses that originally came with a gas water heater and stove are fed with a 240 volt center tapped transformer secondary fused at 100 amps. This explains the 3 wires. Houses that did not have gas are wired the same way but fused at 150 amps. I have seen large houses with 200 and 300 amp power drops. Some older houses only got 50 or 60 amps.
Individual appliance and lighting circuits inside the house are wired from CT to one secondary hot lead giving 120 volts. The typical fuse is 20 amps, the typical outlet rating is 15 amps. Thus it is possible to smoke a wall outlet without tripping the breaker. I have not done this yet but Sherri has....twice! A standard outlet should be able to supply 1800 watts IF the house was correctly wired. Many houses, including mine use a "shared neutral" wiring scheme which makes drawing a big load for a long time on a single outlet a bad idea. This wiring scheme in no longer allowed by code in south Florida. It may still be acceptable elsewhere.
Large electric consumers like the water heater, the clothes dryer, the stove, the pool pump, and the air conditioner are all fed from the entire transformer secondary receiving 240 volts. Common breaker ratings run from 20 amps for the pool pump to 60 amps for the clothes dryer and the stove.
Thus it is possible to get access to 14+ killowats of power in my house by tapping into the clothes dryer outlet, and I have done this to run a ceramic kiln. Due to the high ambient temperature in south Florida another 14 killowatts or so of air conditioning may be needed to remove the added heat generated by the load. This fact is often considered and specified in large computer installations.
Where I live high up, 3 phase is wired for washmachine/cooker and hot water. The rest of the wall sockets have single phase 230. Max P is 2kW per phase before breaker trips....no more and then the line volts sinks to 215. So can't have flat screen TV and kettle on at the same time.
Also I am billed for poor power factor...seems hardly fair despite the poor quality waveform in the pic..... some farmer is using an electric cattle fence most likely incorrectly wired and spiking. The line distortion is very high too.
richy
Also I am billed for poor power factor...seems hardly fair despite the poor quality waveform in the pic..... some farmer is using an electric cattle fence most likely incorrectly wired and spiking. The line distortion is very high too.
richy
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That looks like a disaster.😱 And you can amplify audio with that poor mains or are you playing on battery.
Aahhhhh ! 😡
And to think that this guy got my Lauderdale job : Francois van Well joins Feadship America - At the Yard - SuperyachtTimes.com
And got it again : Merle Wood Announce new sale as the 2010 MYS gets underway
(please say he looks fag, or at least fruity)
Haaa ! Much obliged, i needed that.
Snags, bugs ? Brrrrr.
9 times 16A/230Vac single phase inside the house here, plus 3-phase for the garage, 34KW gas heater for the pool.
(at minus who cares below sea level, thanks to ground water level adjusting. With a separate well and drainage pipes installed across the entire terrain, i can dig 2ft without hitting ground water. Multiple poored concrete 7ft basements below the house)
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