Post by excoriator on May 23, 2017 21:42:14 GMT
I wonder if it's time to change back to DC?
AC won over DC because the transformer (which doesn't work on DC) allowed voltages to be cranked up and down at will. You need high voltages to transmit power over long distances to minimise losses but obviously you cannot have these high voltages in the home. Transformers and AC solved that. It is not a trivial problem, Edison believed in DC, but could not supply power more than half a mile or so from his generating plant. That finished it.
But these days it is no longer true. Almost all electronic kit works on DC, and deriving this from AC is no longer done with a mains transformer. The mains is usually rectified to 400 volts DC, and a dc-dc converter used to convert this down to 5 volts or whatever. The power supply units will accept DC as happily as AC and run perfectly well. Most of them will run on a very wide range of voltages too, and will accept 110 volts as happily as 240 volts. Lights are indifferent to voltage as are electrical heaters. Washing machines will probably run on DC too. They tend to rectify the AC mains to 400V DC and then convert this DC to variable frequency AC to control the motor speed. You'd probably have to have a pump with a DC motor on it, which is easy enough. Fridges and freezers would have to have DC motors. You'd need to change the meter too.
The fact is that these days DC-DC converters are smaller simpler and cheaper than the old AC transformers. They are used in HVDC links because HVDC is MUCH bettr for long distance power transmission than AC. You don't need to keep the conductors as far apart as possible. They can be combined into a single cable, and it can be buried, or taken underwater as required. You don't need miles of pylons, and the cable itself can hold significant amounts of energy, easing problems of sudden loss of a generator. The Utilities would not have to maintain a constant frequency and a tightly controlled voltage. It could wander about from 110 volts to 400v without anything malfunctioning.
It would take rather more than the effort to switch from coal to natural gas, but it is certainly doable, and it has many advantages. Our use of AC is really the result of our inability to transform DC, but we are no longer constrained by this. We should not be afraid to move on of it is to our advantage to do so.
it is worth noting that windmills and solar panels all produce DC which is transformed to mains AC using a DC-AC converter called an inverter. It seems perverse to change to AC when the first thing that is done in most of the appliances that use it is to convert it back to DC again!
AC won over DC because the transformer (which doesn't work on DC) allowed voltages to be cranked up and down at will. You need high voltages to transmit power over long distances to minimise losses but obviously you cannot have these high voltages in the home. Transformers and AC solved that. It is not a trivial problem, Edison believed in DC, but could not supply power more than half a mile or so from his generating plant. That finished it.
But these days it is no longer true. Almost all electronic kit works on DC, and deriving this from AC is no longer done with a mains transformer. The mains is usually rectified to 400 volts DC, and a dc-dc converter used to convert this down to 5 volts or whatever. The power supply units will accept DC as happily as AC and run perfectly well. Most of them will run on a very wide range of voltages too, and will accept 110 volts as happily as 240 volts. Lights are indifferent to voltage as are electrical heaters. Washing machines will probably run on DC too. They tend to rectify the AC mains to 400V DC and then convert this DC to variable frequency AC to control the motor speed. You'd probably have to have a pump with a DC motor on it, which is easy enough. Fridges and freezers would have to have DC motors. You'd need to change the meter too.
The fact is that these days DC-DC converters are smaller simpler and cheaper than the old AC transformers. They are used in HVDC links because HVDC is MUCH bettr for long distance power transmission than AC. You don't need to keep the conductors as far apart as possible. They can be combined into a single cable, and it can be buried, or taken underwater as required. You don't need miles of pylons, and the cable itself can hold significant amounts of energy, easing problems of sudden loss of a generator. The Utilities would not have to maintain a constant frequency and a tightly controlled voltage. It could wander about from 110 volts to 400v without anything malfunctioning.
It would take rather more than the effort to switch from coal to natural gas, but it is certainly doable, and it has many advantages. Our use of AC is really the result of our inability to transform DC, but we are no longer constrained by this. We should not be afraid to move on of it is to our advantage to do so.
it is worth noting that windmills and solar panels all produce DC which is transformed to mains AC using a DC-AC converter called an inverter. It seems perverse to change to AC when the first thing that is done in most of the appliances that use it is to convert it back to DC again!