Harmonics on AC power from switching supplies
Harmonics on AC power from switching supplies
(OP)
I do understand that putting alot of switching power supplies (talking 1000 500W units) can cause issues with harmonics on the AC feed.
First, whats the main cause of this?
Second, using a type K transformer is supposed to help? Or what can be done to help this?
The customer is seeing more issues when running off a UPS vs the main power feed, but his power isnt very clean to begin with.
First, whats the main cause of this?
Second, using a type K transformer is supposed to help? Or what can be done to help this?
The customer is seeing more issues when running off a UPS vs the main power feed, but his power isnt very clean to begin with.






RE: Harmonics on AC power from switching supplies
The better the device, the smaller the resultant harmonic. But there will always be SOME distortion. As the number and size of these devices increases, so does the amount of harmonics, which to NOT tend to statistically cancel out.
RE: Harmonics on AC power from switching supplies
"Venditori de oleum-vipera non vigere excordis populi"
RE: Harmonics on AC power from switching supplies
Mike
RE: Harmonics on AC power from switching supplies
I really don't have much more to go on other than looking at some waveforms of the voltage and current that were emailed to me. I don't know how to attach a file here, but some of the current waveforms are approaching what can be said.....not much of a sine wave component left.
I'm just looking for something I can point these guys to look at, its our gear but not our UPS so I don't need to solve it, but makes us look better if we can.
Sorry that I don;t have much other info, guess I was looking for a magic bullet of sorts....maybe a sine wave filter on the output of the UPS?
RE: Harmonics on AC power from switching supplies
What triplen harmonics do though, is circulate in the delta winding of delta-wye (harmonic source on the wye side) transformers.
Taking half the load and phase shifting it 30 degrees will cause the fifth and seventh harmonics to cancel. Additional load splitting and phase shifting will help deal with the eleventh and thirteenth harmonics (from 12 pulse rectifiers).
Because there is a certain amount of small, but random, phase shifting during harmonic production, there is always some canceling, and the more harmonics produced the more of this type of cancelation happens.
RE: Harmonics on AC power from switching supplies
"Venditori de oleum-vipera non vigere excordis populi"