Disagree. The classical lights dimming when a table saw is under load is a clear indication of a voltage drop. We all know that it is poor practice to have your lighting on equipment circuits but you don't need a mile of cable for voltage drop to become relevant. Since we don't put lighting on high load circuits we cant see the voltage drop but there are other indications that we can still hear and feel when the motor is under high load conditions which in some part may be exacerbated by a line droop to some degree.
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Disagree. The classical lights dimming when a table saw is under load is a clear indication of a voltage drop. We all know that it is poor practice to have your lighting on equipment circuits but you don't need a mile of cable for voltage drop to become relevant. Since we don't put lighting on high load circuits we cant see the voltage drop but there are other indications that we can still hear and feel when the motor is under high load conditions which in some part may be exacerbated by a line droop to some degree.
No Worries Chris, happens to me all the time, especially on subjects like this where there are so many variables. I'm not to the point yet where I actually have "folders" I've just got a big box of paper filled with facts, myths, and confusion. I'm trying desperatley to get them all organized which is why I have so my questions.
Thanks again for your help!
Travis
That example is NOT voltage drop.
A voltage drop occurs when you run exceptionally long power cables over long distances, causing more resistance in the line due to the added copper. For example if I happened to be building a wooden fence in my yard, and I ran a 300 foot extension cord, my voltage going in would be 120v but at the end of the cord it might only be 105 volts. A tool can only tolerate so much Voltage Drop (typically 105v for a 120v circuit). It will still run, but you will start to loose efficiency because the motor is "slipping" in the magnetic field. This just makes the motor inefficient, and it has to use more AMPERAGE to compensate, which can often just trip a breaker.
This is why the power company has transformers right in front of your house, you can run Alternating Current at very high voltages and relatively low amperages, with a lot less copper, and line loss. When it gets to your house, the voltage has to be dropped and the amperage boosted with a transformer so you can plug in your saw.
When the Motor is starting up or is under load, it is drawing more AMPERAGE, the reason the lights dim, is because you are starving them of current.
Example: Your circuit can handle 20A you have lights plugged into the circuit which draw 2 amps, you have a saw that under load draws 18 amps. Any small flux in load, and your lights go.
Solution: Run 240 to the circuit, and it will only draw 9 amps now (4.5 amps per leg). It is the exact same WATTAGE or WORK being done, but it only works the WIRES a quarter as hard.
As a side benefit, you have more amperage available for startup, so it will start faster, and work harder.
So please tell us how a simple resistive device, such as an incandescent lightbulb, dims without a voltage drop occurring?
We are arguing over semantics, I truly believe that we both agree, we are just calling this a different name.
I know that when you consume a surge of power, the power available will temporarily drop.
That means when you encounter a large load in an electrical system, more current will be demanded, which eats up part, or all of your available current. Because of Ohm's Law, amperage and voltage are directly proportional. When one drops the other drops. So yes, a lightbulb will dim when a surge of power is required. However, your voltage will climb back up to 120 again *** Even while you are pulling amperage from the system *** The system does not stay at a lower voltage for the duration of use. If you want to see this, unplug your saw from the wall, and use a small extension cord with three plugs, plug your saw into one of the plugs, plug your meter into the other, and turn your saw on. You will see a temporary drop of voltage when you turn the power on. But after that the voltage will go back to normal, even when the saw is running. The voltage stays constant.
But the term "Voltage Drop" in electrical work is synonymous with "Line Loss"
It is an indication of how much Voltage gets to the end of a copper wire. It is used to indicate how efficient an electrical circuit is.
From Wikipedia:
"Voltage drop is the reduction in voltage in an electrical circuit between the source and load. In electrical wiring national and local electrical codes may set guidelines for maximum voltage drop allowed in a circuit, to ensure reasonable efficiency of distribution and proper operation of electrical equipment (the maximum permitted voltage drop varies from one country to another)[1].
Voltage drop may be neglected when the impedance of the interconnecting conductors is small relative to the other components of the circuit.
For example, an electric space heater may very well have a resistance of ten ohms, and the wires which supply it may have a resistance of 0.2 ohms, about 2% of the total circuit resistance. This means that 2% of the supplied voltage is actually being lost by the wire itself.
Excessive voltage drop will result in unsatisfactory operation of electrical equipment, and represents energy wasted in the wiring system. Voltage drop can also cause damage to electrical motors.
In electronic design and power transmission, various techniques are used to compensate for the effect of voltage drop on long circuits or where voltage levels must be accurately maintained. The simplest way to reduce voltage drop is to increase the diameter of the conductor between the source and the load which lowers the overall resistance."
http://en.wikipedia.org/wiki/Voltage_drop
To see this, hook 3 hundred foot extension cords up end to end to end. Plug your 3 headed plug in again last, and plug in your saw and meter. BEFORE starting the saw, you will have LESS than 120 volts, probably 105-110. This is voltage drop. Turn your saw on and you will get a drop from the original voltage again temporarily, until the voltage climbs back to where it started.
You just used an incorrect term, like if I said "I fried the engine on my saw" you could say, "It's actually a MOTOR not and ENGINE"
We both agree that 240v is DEFINITELY better than 120, and having a separate circuit for lights and power tools is also a very good idea.
I know that when you consume a surge of power, the power available will temporarily drop.
That means when you encounter a large load in an electrical system, more current will be demanded, which eats up part, or all of your available current. Because of Ohm's Law, amperage and voltage are directly proportional. When one drops the other drops. So yes, a lightbulb will dim when a surge of power is required. However, your voltage will climb back up to 120 again *** Even while you are pulling amperage from the system *** The system does not stay at a lower voltage for the duration of use. If you want to see this, unplug your saw from the wall, and use a small extension cord with three plugs, plug your saw into one of the plugs, plug your meter into the other, and turn your saw on. You will see a temporary drop of voltage when you turn the power on. But after that the voltage will go back to normal, even when the saw is running. The voltage stays constant.
But the term "Voltage Drop" in electrical work is synonymous with "Line Loss"
It is an indication of how much Voltage gets to the end of a copper wire. It is used to indicate how efficient an electrical circuit is.
From Wikipedia:
"Voltage drop is the reduction in voltage in an electrical circuit between the source and load. In electrical wiring national and local electrical codes may set guidelines for maximum voltage drop allowed in a circuit, to ensure reasonable efficiency of distribution and proper operation of electrical equipment (the maximum permitted voltage drop varies from one country to another)[1].
Voltage drop may be neglected when the impedance of the interconnecting conductors is small relative to the other components of the circuit.
For example, an electric space heater may very well have a resistance of ten ohms, and the wires which supply it may have a resistance of 0.2 ohms, about 2% of the total circuit resistance. This means that 2% of the supplied voltage is actually being lost by the wire itself.
Excessive voltage drop will result in unsatisfactory operation of electrical equipment, and represents energy wasted in the wiring system. Voltage drop can also cause damage to electrical motors.
In electronic design and power transmission, various techniques are used to compensate for the effect of voltage drop on long circuits or where voltage levels must be accurately maintained. The simplest way to reduce voltage drop is to increase the diameter of the conductor between the source and the load which lowers the overall resistance."
http://en.wikipedia.org/wiki/Voltage_drop
To see this, hook 3 hundred foot extension cords up end to end to end. Plug your 3 headed plug in again last, and plug in your saw and meter. BEFORE starting the saw, you will have LESS than 120 volts, probably 105-110. This is voltage drop. Turn your saw on and you will get a drop from the original voltage again temporarily, until the voltage climbs back to where it started.
You just used an incorrect term, like if I said "I fried the engine on my saw" you could say, "It's actually a MOTOR not and ENGINE"
We both agree that 240v is DEFINITELY better than 120, and having a separate circuit for lights and power tools is also a very good idea.
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You can string 10 MILES of extension cord together and it would read 120V at the end with a typical high-impedance voltage meter and the saw turned off.
If you read the link you previously offered up, it contradicts your own position where the author says....
"What actually happens in situations where there is excessive wiring resistance is that the supply voltage at the motor terminals drops below the nameplate’s acceptable value (usually 105 VAC)"
and he continues on...
"Voltage drop in the wiring is not normally a significant issue – but it can be."
I'm for clarity, and its my belief that your statements are very muddy or just wrong
Once again you talk about how "the power available will temporarily drop"
The lightbulb does not dim due to a lack of POWER it dims to a lack of VOLTAGE.
POWER != VOLTAGE
At this point in time I'm gonna try hard to not reply further because I think the most salient points have been made.
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