Phase To Neutral Calculations
Phase To Neutral Calculations
(OP)
I am planning to run a series of e-ballasts on phase to neutral power, with an equal number of ballasts on each phase for a balanced load. The phase to phase difference is 400v do I use that or the 400/SQRT(3)v when calculating watts. It doesn't seem right that when you calculate watts using
Watts =V*I*pf*SQRT(3)
The answer is greater than the sum of all the ballasts watts. Am I missing something here?
Also am I right in assuming that line and phase voltage can be considered the same if your running the same number of identical ballasts on each phase.
Watts =V*I*pf*SQRT(3)
The answer is greater than the sum of all the ballasts watts. Am I missing something here?
Also am I right in assuming that line and phase voltage can be considered the same if your running the same number of identical ballasts on each phase.






RE: Phase To Neutral Calculations
RE: Phase To Neutral Calculations
3 Phase Watts: SQRT(3)* V(L-L)* I * pf
1 Phase Watt: V x I x pf
RE: Phase To Neutral Calculations
dpc and zazmat are correct, in addition, base on zazmat formula.
Basic Ohms Law;
P(Watts) = V x I x pf (eq. 1)
Where;
V = Voltage, per your post, it is 400Volts
I = Current
pf = power factor, assumed as 1
Since you will buy lighting fixtures, the fixtures is complete with lamp and ballasts.
Let us assume 1 Lamp (40 Watts) per fixture. Sometimes, fixture has more than 1 lamp.
To find the line current (I);
From eq. 1;
I (Current) = P(Watts) / V (Voltage) x pf (Power Factor)
Substitute the given data;
I = 40/ 400 x 1
I = 0.1 Ampere
Your last question is confusing. Let me know the following.
1. Does your panelboard a 3-Phase, 4 wire?
2. What is the rated voltage of your input power supply.
If we follow your phase-phase voltage above, it should be 692.8 Volts.
Regards
Bilegan
RE: Phase To Neutral Calculations
1> Select your ballasts for either 400 volts or 230 volts.
2> Use the nameplate watts to determine the energy consumption.
3> Use the nameplate amps to determine the circuit loading and KVA.
4> If you use 400V fixtures you must connect them phase to phase and use a 2 pole breaker.
5> If you use 230V fixtures you must connect them phase to neutral and use a 1 pole breaker.
6> If you connect from phase to neutral you can not use a floating neutral. The neutral must be connected back to the supply transformer neutral.
7> There will be harmonic currents on the neutral and the neutral size must not be reduced.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Phase To Neutral Calculations
(4) Each fluorescent luminaire installed on branch circuits with voltages exceeding 150 volts-to-ground shall be:
(a) Provided with a disconnecting means integral with the luminaire that simultaneously opens all circuit conductors between the branch circuit conductors and the conductors supplying the ballast(s); and
(b) Marked in a conspicuous, legible, and permanent manner adjacent to the disconnecting means, identifying the specific purpose
RE: Phase To Neutral Calculations
What do they mean by "disconnecting means intergral with the luminaire"? This sounds to me that a switch has to be integrated, that is, a part of, the luminaire. This doesn't sound practical, so I must be interpreting it incorrectly.
K2ofKeyLargo
RE: Phase To Neutral Calculations
Bill
--------------------
"Why not the best?"
Jimmy Carter