UL 810B-2016 pdf download

UL 810B-2016 pdf download.Standard for DC Power Capacitors.
18.5.3 lf, after repeating this procedure several times the remaining capacitance is higher than zero, or10% of the initial value in case of self-healing capacitors with segmented or special un-segmented design:
a)Another sample may be used,and/or the test voltage and test time may be increased; or
b) The capacitor unit is to be subjected to an externally operated overpressure until thedisconnector or the overpressure detector has operated. The value of this pressure is to begiven by the manufacturer
18.5.4 When the test procedure is stopped, the capacitor is cooled to the ambient temperature, and theDielectric Voltage Withstand Tests of Section 14 are conducted.If the capacitor internal protection hasoperated, no dielectric voltage withstand test between terminals,14.2 is conducted.
18.5.5 ln case of self-healing capacitors with segmented or special un-segmented designs,othermethods to demonstrate the ability of a capacitor to lose more than 90% of its capacitance may be agreedbetween manufacturer and user.
19 Internal Fuse Operation Test19.1 General
19.1.1 This test applies to non-self-healing capacitors fitted with internal current fuses. The fuse isconnected in series with the element(s) which the fuse is intended to isolate if the element(s) becomefaulty.
19.1.2 The operation of an internal fuse is generally determined by one or both of the following factors:
a) The discharge energy from elements or capacitor units connected in parallel with the faultyelement or capacitor unit; and/or
b) The available fault current.
19.1.3 lf the capacitor is intended to be protected by an external fuse, the test is carried out with theexternal fuse suggested by the capacitor manufacturer.
19.3 Test procedure
19.3.1 The test is carried out at the upper and at the lower voltage limits on capacitors with inducted faultsin accordance with 19.3.4.
19.3.2 The upper DC test voltage uU2 outlined in 19.2 is applied until at least one fuse has failed. Thevoltage is then immediately reduced to 0.8 U until a second fuse fails.
19.3.3 The voltage across the capacitor shall be measured throughout the test. lf the voltage immediatelybefore and immediately after the fuse operates differs by more than 10 %, the test shall be repeated, withextra capacitance connected in parallel to the capacitor under test. This test may be repeated on a newcapacitor.
19.3.4 One of the following capacitor element faulting procedures (a),(b).(c), (d) or an alternative methodshall be used to prepare the samples prior to testing:
a) Mechanical puncture of the element
Mechanical puncture of the capacitor element is made by a nail,which is forced into theelement through a pre-drilled hole in the container.
NOTE 1- Puncture of only one element cannot be guaranteed.
NOTE 2 – Iln order to limit the possibility of a flashover to the container along the nail, orthrough the hole caused by the nail, a “nailmade of insulating material may be used andorthe punctures may be performed in the element connected permanently, or during the test, tothe container.
b) Electrical breakdown of the element (first method)
Some elements in the test capacitor sample are to be provided with, a tab or similar, insertedbetween the dielectric layers.Each tab is connected to a separate terminal.
To obtain breakdown of an element thus equipped, a surge voltage of sufficient amplitude isapplied between the tab and one of the foils of such a modified element. Capacitor currentand/or voltage shall be recorded during the test.
c) Electrical breakdown of the element (second method)
Certain elements in the test capacitor sample are to be provided with a short fusible wireconnected to two extra tabs and inserted between the dielectric layers,each tab beingconnected to a separate insulated terminal.
To obtain breakdown of an element equipped with this fusible wire, a separate capacitor
charged to a sufficient energy is discharged into the wire in order to open it. Capacitor currentand/or voltage shall be recorded during the test.
d) Electrical breakdown of the element (third method).