(i) Positive voltages cause comparatively more corrosion in metal than negative voltages. (ii) Negative voltages are safer for human body while doing Telecom activities. (iii) Lightning may cause positive voltages in the equipment circuitry. In that case, negative voltages (lack of electrons) neutralize positive charges and prevent excessive heat. (iv) Negative voltage is safer for long telephone line for transmitting power trough it. The reson for electing -48V in reference to ground is to avoid the nasty galvanic effects in telephone cabling. +48V would have nastier effect on wet cabling.
Telecom carriers use -48vDC because it is easy to store in deep cycle batteries and can backup equipment during a power outages for much more time than a regular UPS. Depending on the load of the equipment you can easily get 8+ hours of backup before having to switch to a Generator.
During older days, telephone cables used to be laid underground. We know that when two metals are at different voltages then electro - depositing process starts and ions of metal at high potential start depositing on metal at low potential. This was the reason telephone circuitry used to be fed -ve supply in earlier days to maintain cables at low potential in comparison to the Earth to stop the gradual decay of telephone cables. All the communication related circuits developed afterwards supported the same practice of maintaining -ve supply to communication system. This is the reason most of the communication systems available today use -ve supply as a power source. Vineet Kumat vineet.kumar@in.abb.com
It is actually 55.2 volts, because it originally started out as the voltage of a serial stack of 24 lead acid cells on charge.
It all goes back to the very early days of telephony where signals had to be transmitted over long distances, before the invention of the triode (audion) tube, so amplifiers were not possible. Consequently a high voltage was needed, but not so high as to cause arcing or other breakdown effects, and not so high as to be dangerous. Thus the 55 volt standard was chosen as a reasonable compromise.
I suspect that the negative polarity would have been chosen because it reduces corrosion. There was a brief period in the 60's when there was a fashion for cars to have negative 12 volt electrical systems, but it caused so many problems that it soon went away.
For better Noise clipping we use -48v as all the noise are on +ve side
48 volts is a convenient safe voltage to use, and telephone systems use a positive earth connection to minimise electroytic damage ot cables.
If a 48 Volt club car electric motor requires 48 volts, then it should be given a 48 volt power source, or something close to it. Too many more volts and it may burn out; not enough volts and it may not run or it will try to draw too much power and burn out the power supply.
A lot of commercial telecommunications equipment runs on 48 volts. There are also relays that use 48 volts. I'm sure there are many other uses for this. I'm not aware of any in a typical house, if that's what you're looking for. Perhaps certain water softeners, sprinkler systems, etc. run on 48, but the ones I've seen usually run on 12.
Power = E times I = (24 x 2) = 48 watts
To convert watts into amperes you divide the circuit voltage into the watts. Amps = Watts/Volts. <<>> Converting Watts to Amps The conversion of Watts to Amps is governed by the equation Amps = Watts/Volts For example 12 watts/12 volts = 1 amp Converting Amps to Watts The conversion of Amps to Watts is governed by the equation Watts = Amps x Volts For example 1 amp * 110 volts = 110 watts Converting Watts to Volts The conversion of Watts to Volts is governed by the equation Volts = Watts/Amps For example 100 watts/10 amps = 10 volts Converting Volts to Watts The conversion of Volts to Watts is governed by the equation Watts = Amps x Volts For example 1.5 amps * 12 volts = 18 watts Converting Volts to Amps at fixed wattage The conversion of Volts to Amps is governed by the equations Amps = Watts/Volts For example 120 watts/110 volts = 1.09 amps Converting Amps to Volts at fixed wattage The conversion of Amps to Volts is governed by the equation Volts = Watts/Amps For Example, 48 watts / 12 Amps = 4 Volts Explanation Amps are how many electrons flow past a certain point per second. Volts is a measure of how much force that each electron is under. Think of water in a hose. A gallon a minute (think amps) just dribbles out if it is under low pressure (think low voltage). But if you restrict the end of the hose, letting the pressure build up, the water can have more power (like watts), even though it is still only one gallon a minute. In fact the power can grow enormous as the pressure builds, to the point that a water knife can cut a sheet of glass. In the same manner as the voltage is increased a small amount of current can turn into a lot of watts.
+24 volts is not normally used for telecom equipment. -48 volts is the usual value. 48 was chosen as a compromise between safety and voltage/power efficiency. Minus was chosen over plus to manage corrosion effects of cabling in underground installations.
It was originally supplied by a large bank of lead-acid batteries, 24 cells in series gave 48V.
48 volts is a convenient safe voltage to use, and telephone systems use a positive earth connection to minimise electroytic damage ot cables.
Voltage is dependent on a reference. If I have a 12 volt battery, and ground the - side, it is 12 volts to ground. If I instead ground the + side, it is -12 volts to ground. -48 volt telecom equipment is simply referenced to ground "upside down" or backwards, giving it a negative sign.
You need to divide the 48 volts by the voltage produced by a single battery.
No.
Negative 48 volt DC voltage is simply a voltage that is negative 48 volts with respect to ground. This voltage is widely used in telecommunication systems.
48 VOLTS
If a 48 Volt club car electric motor requires 48 volts, then it should be given a 48 volt power source, or something close to it. Too many more volts and it may burn out; not enough volts and it may not run or it will try to draw too much power and burn out the power supply.
A lot of commercial telecommunications equipment runs on 48 volts. There are also relays that use 48 volts. I'm sure there are many other uses for this. I'm not aware of any in a typical house, if that's what you're looking for. Perhaps certain water softeners, sprinkler systems, etc. run on 48, but the ones I've seen usually run on 12.
Lead-Acid cells are generally considered to deliver 2 volts, so you'd need 24 cells to get 48 volt. Easiest way of doing that would be to use two 24V batteries as used in truck and heavy vehicles.
This voltage is supplied by large banks of lead-acid batteries at the central office. There are 24 cells in each battery, giving 48 volts. Grounding the positive battery terminal makes the delivered voltage negative. Batteries are used so the system can keep operating (for a period of time) during a power failure, so that emergency and other important calls can still be made.