UPS DC Bar
UPS DC Bar
(OP)
Hi, I wonder how is the DC bar of an online ups can be kept constant? I mean if your utility voltage is fluctuating in a wide range, so it means your DC voltage rectified on DC busbar will behave also so isnt it? I guess to be able to chop the voltage on this bar it is needed that this voltage must be constant ,at least I guess so..






RE: UPS DC Bar
The output voltage of a UPS is usually kept constant, no overvoltage if grid voltage goes up. But if input voltage goes below output voltage, the latter is also reduced.
There are more sophisticated input stages for UPS. Like sine forming and AFE rectifiers. Everything can be had. But cheapo UPS don't have those features.
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: UPS DC Bar
RE: UPS DC Bar
Others work more intimately with UPS and will surely add/comment later today.
Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: UPS DC Bar
Without getting too mathematical, the output of the rectifier was approximately:
Vdc = 1.35 * Vac * cos alpha
where Vac is the line to line incoming voltage
cos alpha is the firing angle of the thyristor.
The resultant output voltage would also be filtered which would remove much of the ripple voltage, using either a DC choke or a DC link capacitor, depending upon the configuration of the inverter.
RE: UPS DC Bar
UPS engineer http://www.calibrepower.co.uk