Hi Dave:
The optocoupler must be rated for the voltage
across the optocoupler. If the high voltage side
is subject to transient overvoltages, then the
optocoupler must be rated to withstand the
transient overvoltages.
IEC 60664-1 defines transient withstand voltages
for mains circuits. If the high voltage side is
120 volts, then the withstand must be 1500 volts
peak. If 220, 230, or 240 volts, the withstand
must be 2500 volts peak.
If the optocoupler is required to be reinforced
(or double) insulation (and it most likely is),
then the withstand voltages are 2500 volts peak
and 4000 volts peak.
The clearance across the optocoupler must be at
least 0.5 mm for basic insulation and 1.5 mm for
reinforced insulation for 120 volts. Clearance
must be at least 1.5 mm for basic insulation and
3.0 mm for reinforced insulation for 220-230-240
volts. (Creepage cannot be less than clearance).
These numbers may not be the same as specified in
60204, 61558, 60747, or UL 1577 (but they are
close). IEC 60664-1 is the basic safety standard
which all other standards must use. Not all
standards committees have followed this rule, nor
have they necessarily understood IEC 60664 series.
Good luck, and best regards,
Rich
From: Nyffenegger, Dave
[mailto:[email protected]]
Sent: Friday, June 26, 2015 10:50 AM
To: [email protected]
Subject: [PSES] Optos for PELV isolation
Hi Folks,
I'm trying to determine the appropriate ratings
for optocouplers to meet PELV isolation
requirements from non-PELV low voltage circuits.
EN 60204-1:2006+A1:2009 6.4.1 c states "live parts
of PELV circuits shall be electrically separated
from other live circuits. Electrical separation
shall be not less than that required between the
primary and secondary circuits of a safety
isolating transformer (see IEC 61558-1 and IEC
61558-2-6 );" The IEC 61558 standards are written
for transformers and I'm not sure how that
translates into specifications available for optos
or to UL 1577 or EN/IEC60747-5-5 that some optos
are approved to. I have seen UL reports testing
optos to UL 1577 "single protection" or and
"double protection" isolators. UL 1577 itself
doesn't clearly define "single" and "double
protection" and I'm currently waiting to hear
back from UL on that.
I am using optos to switch on a non-PELV circuit
from a PELV circuit. Does anyone know if optos
approved to UL 1577 Single protection and/or
Double protection and/or EN/IEC60747-5-5 meet the
EN 60204-1 requirements for PELV isolation from
non-PELV circuits?
Thanks
-Dave
David P. Nyffenegger, PMP, SM-IEEE
Product Development Manager
Bell and Howell
3791 South Alston Avenue
Durham, NC 27713
Phone: 919.767.6419
Web: <http://www.bellhowell.net/>
www.bellhowell.net
-
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