I read in !emc-pstc that don_borow...@selinc.com wrote (in
ofae2c2f5d.695d080d-on88256cbc.00568...@selinc.com) about
'Applicabilty of Flicker Standard' on Tue, 28 Jan 2003:
We are trying to figure out the applicability of 61000-3-3 Flicker Standard
to the power supply in our product. We have a device that may be hard
wired into the public low voltage (230 V) mains under certain
circumstances, and has no mains switch. Given this, it appears that the
maximum relative voltage change dmax shall not exceed 4% (61000-3-3,
Section 5, Limits, condition a.) since it is energized immediately on
restoration of supply after a power supply interruption.
Question 1: Does the 4% dmax include the inrush upon restoration of supply,
or does it apply only to voltage changes caused by changes in current
demand during operation (after inrush)?
It includes the inrush current. The standard is NOT only about flicker;
this impression is due to the less-than-generalized title. It is about
all sorts of **voltage changes** impressed on to the supply by loads.
See the Amendment for better information on inrush current.
To make things even messier, the device in question is a control for a
power distribution recloser (over 1 kV). During a fault, it might demand
enough current to exceed 4% dmax when operating the recloser. The public
low voltage powering the control would almost certainly be derived from the
high voltage system being switched by the recloser.
Question 2: Do we need to meet the 61000-3-3 limits during recloser
operation (most likely fault conditions)?
Probably not if it is installed within a utility's site. AIUI, any low-
voltage supply there is not a 'public' supply. If it can be installed in
a user's premises, then the low-voltage supply might not be derived from
the MV supply being switched (in a big hospital, for example, which has
two separate HV or MV supplies for reliability). In that case, the
standard applies.
--
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
Interested in professional sound reinforcement and distribution? Then go to
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