Re: [PSES] Fuse designations

[Bill Owsley]

 An aside related to delayed fuses.
Two issues with the subject came up when I was an intern a few decades ago.
The fuses were used in ELV circuits so could be touched in application.  In 
use, they got too hot to touch, so said the safety folks.  Tasked with finding 
a lower touch temp fuse to use.  Samples from every vendor and some never heard 
of.  Found one, half the resistance, and temp.  But unknown source so lots of 
testing to evaluate performance.
Then found that the in-rush current at each turn-on affected the delay 
mechanics.  The fuse used a little solder cup and spring to make connects, and 
each in-rush caused a slight slip.  5-10 turn on's and it would open.  Power 
supply engineers found a way to limit in-rush current to avoid the condition.
Saw this in-rush issue over and over in the following decades.

Bill Owsley
EMC First LLC


On Wednesday, March 2, 2022, 05:44:09 PM EST, Douglas E Powell 
 wrote:  
 
 Very nice, thanks.
Now I may need to convince my client to stop using Slow Blow on international 
shipments.
-Doug

Laporte, Colorado USA
LinkedIn

(UTC -07:00) Mountain Time (US-MST)



On Wed, Mar 2, 2022 at 3:34 PM Scott Aldous 
<0220f70c299a-dmarc-requ...@listserv.ieee.org> wrote:

Hi Doug,
As the link Rich provided from Littelfuse indicates, the international symbols 
come from IEC 60127-1. See the last page of this preview, section 6.1.
On Wed, Mar 2, 2022 at 2:22 PM Richard Nute  wrote:


 

 

Here is some info:

 

https://www.swe-check.com.au/pages/learn_fuse_markings.php

https://www.littelfuse.com/~/media/files/littelfuse/technical-resources/documents/reference-documents/littelfuse_5x20mm-iec-fuse-cap-marking_guide.pdf

 

Rich

 

 

 

From: Brian Kunde  
Sent: Wednesday, March 2, 2022 1:08 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] Fuse designations

 

I do not know where the information I have originally came from, but I got this 
and have been using this for over 30 years:

 

FF = Very Fast Acting

F = Fast Acting (Common)

M = Medium Time Lag

T = Time Lag (Common)

TT = Long Time Lag

 

I got this from Bud Lang who was our Safety Guru at Heath Kit many years ago.  

 

The Other Brian

 

On Tue, Mar 1, 2022 at 5:33 PM Douglas E Powell  wrote:


All,

 

Over the years, I've seen various ways people include a caution or warning, in 
their user documents or product labels, for replacement fuses. Similar to: 
"replace only with same type and rating of fuse";  followed by a code: 
T1.6AH250V. And for those who may not understand the code, they may sometimes 
add in parentheses some variant of "(1.6 Amp time-lag, ~250V, high breaking 
capacity)". 


So now to my question, US manufacturers sometimes use the phrase "SLO-BLO" or 
"Slow Blow" instead of Time-Lag or Time-Delay.  Are these terms commonly used 
internationally and if so, are they clearly understood?

 

I took some time to look up SLO-BLO and found it's a registered trademark for 
Littelfuse going back to 1957, and it has been continuously renewed since that 
time.


Incidentally, a German Engineer once told me the way he would designate a fuse 
type for a variety of tripping characteristics was in this order from very slow 
to very fast: TT1.0A250V, T1.0A250V, 1.0A250V, F1.0A250V, FF1.0A250V.

 

Thanks, -Doug

 

 

Douglas E Powell

Laporte, Colorado USA

 

(UTC -07:00) Mountain Time (US-MST)

 





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Re: [PSES] RoHS3 Inquiry Allowable Content

[Chris Wordley]

Hi Chris

Firstly, ‘RoHS2’ and ‘RoHS3’ means different things to different people, so it 
is probably best to refer to the specific legislation e.g. EU Directive 
2011/65/EU. 

Under this Directive, the concentration limits for the 4 phthalates (that were 
added by Delegated Directive (EU) 2015/863) is 0.1% by weight in each 
homogeneous material, however small. 

Chris 


> On 3 Mar 2022, at 14:26, Chris Willette 
> <190af967ec2e-dmarc-requ...@listserv.ieee.org> wrote:
> 
> Hi 
>  
> Within RoHS3 is there allowable tolerance content for the 4 new substances, 
> eg. It is less than 2 grams it is not applicable?
>  
> Have a connector which is RoHS2 compliance it does not meet RoHs3, because of 
> a very small O-ring around
> the connector’s perimeter.  Within RoHS3 is there an allowable content for a 
> very small piece or is it zero tolerance?
>  
> I  believe RoHS3 has zero tolerance other than the % listed, but was curious 
> if others had a similar situation
> where a very small piece of a component didn’t meet RoHS3 but majority of 
> component met RoHS3?  
>  
> Thanks
>  
> -- 
> 
> This e-mail and any attachments may contain information that is confidential 
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> 
> If you are not the intended recipient, please notify me immediately by 
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