Harmonic effects on breaker selection.
Harmonic effects on breaker selection.
(OP)
Does any one have a rule of thumb or some insite for sizing the main breaker for a panelboard that is going to be used to power computer equipment. Since the load will be 100% non-linear, should the breaker be oversized to makeup for the harmonic currents. The loads will be 208V and 120V. I believe the power conductors should be sized at 125% and the neutral should be sized at 200% of the calculates load.
Thank You,
Ed
Thank You,
Ed






RE: Harmonic effects on breaker selection.
If you are really concerned, you can use true rms sensing breakers which are widely available (in the USA again) for 225A and above.
On the other hand our experience has shown that we seldom see a main breaker loaded more than its 50-60% capacity as we always run out of physical space of the branch circuits much before we utilize the rated capacitiy of a panelboard or MCB.
In last 15 years of experiecne not once anyone has complained about harmonic related tripping or issues in any data centers that I have dealt with. It may be because most of such facilites are properly or adeqautely designed.
However, I have recently heard of 200A breakers tripping at 170 or 180 amps feeding some temporary facilities with signinficant harmonic loads (no measured data avaialble, yet), if this gives you any ideas. Bear in mind these reported breakers were operatinng under less than ideal conditions such are high ambient etc.
I am sure someone with more research information will post further answers.
RE: Harmonic effects on breaker selection.
RE: Harmonic effects on breaker selection.
I have a better idea on how to handle my design.
edryder
RE: Harmonic effects on breaker selection.
RE: Harmonic effects on breaker selection.
Insatalltion without true rms sensing metering, may not realize that they are approching trip because of harmonics.
RE: Harmonic effects on breaker selection.
RE: Harmonic effects on breaker selection.
I agree with all above posts. There's no particular unusual sizing requirements for phase conductors/protection associated with harmonics.
Triplen harmonics can add constructively on the neutral to about 173% of phase current, that's why 173% or 200% neutral conductors are often specified. There's no similiar issue involved with the phase conductors, though.
RE: Harmonic effects on breaker selection.
I wouldn't bother with that finance company that makes jet engines tho. They're not even "Good Enough" to me anymore.
RE: Harmonic effects on breaker selection.
RE: Harmonic effects on breaker selection.