Amperage on 3 phase
- Thread starter ericmen30
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iMuse97
Senior Member
- Location
- Chicagoland
amperage and voltage are inversely proportional with a given load. increase the amperage: the voltage need not be as great. increase the voltage: the amperage is proportionately less. Ohm's Law is not an opinion; it's a law of Nature, or nature's God, in the words of T. Jefferson.
Generator output is usually rated in kVA.
Thus, for the same kVA at 208V as at 480V, you need more current (A) to keep the kVA the same.
It's no more complex than that.
Pierre C Belarge
Senior Member
- Location
- Westchester County, New York
The inversely proportion theory can be thought of like a seesaw.
One side of the seesaw is voltage and the other side of the seesaw is amperage.
If the voltage goes up, the amperage goes down.
If the amperage goes up, the voltage goes down.
One side of the seesaw is voltage and the other side of the seesaw is amperage.
If the voltage goes up, the amperage goes down.
If the amperage goes up, the voltage goes down.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
How about a different explanation?
A generator (and other sources) has a given power capability. Just like a dual-voltage motor or transformer, there is more than one set of output windings that can be connected together in different ways.
Think of a pair of flashlight batteries, each with a 1.5v output and, let's say, a 1a current capacity. If you connect them in parallel, you have a 1.5v, 2a supply; if you connect them in series, it's 3v at 1a.
Both of those connections can supply as much as (since P = E x I, either 1.5 x 2 or 3 x 1) three watts of power. The generator is the same way. The output voltage depends on the various internal connections.
Obviously, the only generator output voltage you care about is that which matches your loads, and the current capacity at that voltage is the most you can supply. If it's not enough, you need a larger unit.
A generator (and other sources) has a given power capability. Just like a dual-voltage motor or transformer, there is more than one set of output windings that can be connected together in different ways.
Think of a pair of flashlight batteries, each with a 1.5v output and, let's say, a 1a current capacity. If you connect them in parallel, you have a 1.5v, 2a supply; if you connect them in series, it's 3v at 1a.
Both of those connections can supply as much as (since P = E x I, either 1.5 x 2 or 3 x 1) three watts of power. The generator is the same way. The output voltage depends on the various internal connections.
Obviously, the only generator output voltage you care about is that which matches your loads, and the current capacity at that voltage is the most you can supply. If it's not enough, you need a larger unit.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Note: this inversely-proportionate relationship between voltage and current occurs because we change the equipment (whether source or load) to suit the design voltage.
It's not the same as a greater higher voltage pushing a greater current through a constant (an unchanged load) resistance, which is a directly-proportionate relationship.
It's also why transmission of electricity at a higher voltage (but at a lower current) can deliver the same amout of power as a lower voltage (but at a higher current.)
Since 'insulation' is cheaper than 'conductor', and voltage drop (wasted energy) is dependent on conductor resistance and current (but not voltage), HV transmission is more efficient.
It's not the same as a greater higher voltage pushing a greater current through a constant (an unchanged load) resistance, which is a directly-proportionate relationship.
It's also why transmission of electricity at a higher voltage (but at a lower current) can deliver the same amout of power as a lower voltage (but at a higher current.)
Since 'insulation' is cheaper than 'conductor', and voltage drop (wasted energy) is dependent on conductor resistance and current (but not voltage), HV transmission is more efficient.
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