Hope you are all fine. Mine is a simple doubt,but affects my back ground . We have a 4 Core Cable running for a street lighting circuit ( 6 number 400w/230V HPS lamps in circuit . Alternate poles are connected in alternate phase and neutral is the 4th conductor . ( like p1,p4 in R & p2,p5 in Y & p3,p6 in B ) . If we need to find the load at the end of the circuit ( total load ) we should use 415V(3ph) or 230 V(1ph).We normally use 415 ,but isn't it true that we give a 1phase supply only ? Can some one clarify .
Voltage - Misunderstanding
- Thread starter premgin
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- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
To be honest I don't understand the info given but if the lights are on one 230V single phase circuit then you would use 230V for the calculation of the circuit. Not sure if that is what you are asking. Hope one of our EE's will pitch in.
DetroitEE
Senior Member
- Location
- Detroit, MI
I would treat this the same as any other 3 phase load. You mention the number 415, so I assume your supply is 240 volts (240*1.73). 2400 Watts/415 = 5.8 Amps.
- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
2400 watts divided by 415 volts and divided again by 1.732 is 3.3 amps. That would be the average of the current on each of the three phases, as measured at the breaker feeding this circuit.
Sounds like a 415Y/240V 3? 4-wire system. For line to neutral loading such as described, to get the line current value you'd divide your total VA (i.e. assuming 1watt = 1VA ? 1pf) by 720V (i.e. 3 ? 240V) for a balanced load...
This is the same as calculating two units per line and dividing by line-to-neutral voltage (2 ? 400VA ? 240V = 3.33A)
Welcome to the forum!
6 units ? 400VA = 2400VA
2400VA ? 720V = 3.33A
2400VA ? 720V = 3.33A
This is the same as calculating two units per line and dividing by line-to-neutral voltage (2 ? 400VA ? 240V = 3.33A)
Welcome to the forum!
It's a three-phase four-wire supply.
Since the load is balances, (2 number 400W unis on each phase) you can calculate it as three single phase 800W loads or one 2400W three phase loads.
A couple of points.
If your system is 415V line to line, the single phase line to neutral voltage would be 240V, not 230V.
I don't what the power factor is for sodium discharge lamps. Without that piece of information you can't calculate currents.
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