From: Scott Aldous
Sent: Friday, May 04, 2007 3:14 PM
If a fuse or circuit breaker is used, then the short circuit
current limit is actually 1000 divided by the open circuit
voltage, per table 2C
Care should be taken here. Maximum available current might not occur at
short-circuit.
From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of
ted.eck...@apcc.com
Sent: Friday, May 04, 2007 2:44 PM
To: oconne...@tamuracorp.com
Cc: emc-p...@ieee.org
Subject: Re: limited current circuits in IT equipment
Hello Brian,
Under IEC 60950-1:2005 clause 2.1.1, bare parts of a SELV
Hello Brian,
Under IEC 60950-1:2005 clause 2.1.1, bare parts of a SELV circuit may be
accessible to the operator. Limited current circuits need not be at SELV
voltages. They are specified as a circuit that doesn't have the current
capability such that there is hazardous energy
Brian -
Contact with an SELV circuit where there's no energy hazard is
acceptable, regardless of other construction features (assuming those
other construction features also comply with the standard).
One presumes your client understand there's a fire hazard associated
with a 10 A circuit.
A customer would like a 10Vdc/8A contact to be exposed to the end user. I
would like to say no because this would not meet the requirement for an
LCC ckt.
But as I read from the sacred scrolls of 60950-1, it was noted that if the
exposed part is not at a Hazardous voltage (reliably SELV) or
I read in !emc-pstc that Rich Nute ri...@sdd.hp.com wrote (in
200109181539.iaa02...@epgc196.sdd.hp.com) about 'Limited Current', on
Tue, 18 Sep 2001:
No, I am not sure that there would be measurable
x-radiation at the faceplate of an 8 kV 1-inch crt.
But, based on the above technical facts, I
Hi John:
Are you sure that you can get appreciable X-radiation at 8 kV? In the
days of monochrome TV with 9 and 12 inch tubes running at 8 kV, we never
bothered about X rays, but projection sets running at 25 kV were known
as a radiation hazard. Maybe tolerance levels have been
I read in !emc-pstc that Rich Nute ri...@sdd.hp.com wrote (in
200109172148.oaa00...@epgc196.sdd.hp.com) about 'Limited Current', on
Mon, 17 Sep 2001:
Beware of x-radiation from this crt. Larger crt's operating
at 8 kV have relatively thick faceplates which attenuate the
x-radiation
.
Except as permitted in 2.4.6, segregation of parts of LIMITED
CURRENT CIRCUITS from other circuits shall be as
described in 2.3 for SELV Circuits
So what this tells me is if the stored charge is less than 45 uC
(2.4.6), it is considered safe with only basic
, segregation of parts of LIMITED
CURRENT CIRCUITS from other circuits shall be as
described in 2.3 for SELV Circuits
So what this tells me is if the stored charge is less than 45 uC
(2.4.6), it is considered safe with only basic insulation? If over the
stored charge limit, it must
PSNet,
Rich is absolutely correct... and this use of the 990 network is
being recommended as an update to 950 - in a future update to the
standard... The advantage of this network is that one does not have to look
at each harmonic individually; the network does that and sums them into
Dear Group,
2.4.2 of UL1950 defines the upper current limit for Limited Current Circuits
when the frequency is above 1kHz as 0.7mA multiplied by the frequency in
kilohertz (up to 70mA peak). Since the limit increases (up to
70mA) as the frequency goes up, one can assume
--- On Thu, 11 Jun 1998 19:50:14 +0900 F.Goto go...@a-pex.co.jp wrote:
Dear Group,
2.4.2 of UL1950 defines the upper current limit for Limited Current Circuits
when the frequency is above 1kHz as 0.7mA multiplied by the frequency in
kilohertz (up to 70mA peak). Since the limit increases
Dear Group,
2.4.2 of UL1950 defines the upper current limit for Limited Current Circuits
when the frequency is above 1kHz as 0.7mA multiplied by the frequency in
kilohertz (up to 70mA peak). Since the limit increases (up to
70mA) as the frequency goes up, one can assume that the human body
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