At what distance is voltage drop a concern for 480V circuits?

M

Mumbaigirl

Member
Location
USA
Occupation
Electrical Engineer
Hello,
Is there a general rule of thumb for 480V circuits without having to actually calculate for the 3% voltage drop?

Thank you,
Jui
 
Voltage drop is dependent upon the load. If you have a 20 amp circuit and you are only drawing 2 amps then you could go a much greater distance than you could if you were drawing 18 or 20 amps.
 
I don't believe voltage has anything to do with the voltage shop formula. Either way the 3% voltage drop is only required for fire pumps. Otherwise the 3% is a recommendation
 
As stated, voltage drop is only dependent on circuit impedance and load current.

But, the relative effect of a given voltage drop is dependent on the circuit voltage.

A given absolute amount of drop is a greater percentage of a lower circuit voltage.

Thus, the higher the voltage, the less detrimental is a given amount of voltage drop.
 
The rule of thumb that I have heard, is you don't have to look close at voltage drop until the length of the circuit is close to the voltage of the circuit. So for a 120 volt circuit, 100', and a 480 volt circuit, 450'.
 
don_resqcapt19 said:
The rule of thumb that I have heard, is you don't have to look close at voltage drop until the length of the circuit is close to the voltage of the circuit. So for a 120 volt circuit, 100', and a 480 volt circuit, 450'.
Click to expand...
Thank you so much! I appreciate it.
 
LarryFine said:
As stated, voltage drop is only dependent on circuit impedance and load current.

But, the relative effect of a given voltage drop is dependent on the circuit voltage.

A given absolute amount of drop is a greater percentage of a lower circuit voltage.

Thus, the higher the voltage, the less detrimental is a given amount of voltage drop.
Click to expand...
Thank you so much! I appreciate it.
 
don_resqcapt19 said:
The rule of thumb that I have heard, is you don't have to look close at voltage drop until the length of the circuit is close to the voltage of the circuit. So for a 120 volt circuit, 100', and a 480 volt circuit, 450'.
Click to expand...
I should have stated the % of the drop will vary with the voltage. For instance 120v with a 12 volt drop is 10%. While at 480V with a 12v dop is only
2.5% drop
 
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