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Suresh R
03/07/06 02:05
Read: 1114 times
Chennai
India


 
#111484 - replies
Responding to: Kai Klaas's previous message
Kai Klaas said:

It's no standard developing practise to test whether a relay can withstand a certain switching stress or not, because all relevant data is already in the datasheet!

Standard design practise is, to choose a relay, where the switching current lies well within the maximum specification. Then, you will not need any additional testing.


Erik said:

Your totally irrelevant circuit does not test if the reed switch get damaged, only if it get destroyed.


iam familiar with the ratings which i have given below. but iam not testing it to use in my circuit but need to do the test and observe the switch life expectancy on such an application (no of cyles passed is to be checked)
succedingly contact resistance, damage in contacts, Ampere turns could also be checked after the test.

So, by doing the above succeding tests i could also take a note on the damage caused to the reed switch after the test.
only samples are tested.

Kai Klass said:

To test your relay by your circuit is a waste of time, because it only tells you whether the relay becomes suddenly destroyed or not, which is rather unlikely to happen in your case.


yes. i can understand it. but i was asked to do so :(
but i hope the test would be resonable in getting familiar with the points you have mentioned below.

Kai Klass said:

Or by other words, stressing the contact beyond maximum specifications does not neccessarily result in a destroyed contact, but in a bad contact, becoming worse and worse with each additional overstressing switching event!


Kai Klass said:

You will find the maximum switching current for model "72" as to be 1.0A. So, if your maximum switching current is 2.6A, then it's just exeeding the maximum specification and your relay will show an early failure in the near future.


For my case, the ON / OFF cycle of the switch is:
10 sec OFF continued by 2 sec ON.
and the switch is going to experience this 2.6A only during the inrush current condition of that 2sec ON period.

specifications:
The reed switch iam testing is tested for 10W/VA capability.
carry current is 1.5A
switching current is .5A

At normal condition (after the inrush current flows) the switch would experience V*I = 12* .291 = 3.5W
At normal condition it satisfies.
But at current inrush (which will be for very less time) the power experienced by the switch seem to go high => 12* .291* 8.8 = 30.7296W.
Since its going to be for very short period will that affect the performance very badly?

suggestions please.

Terry said:

The 40 ohm resistor will limit the inrush and final current as well THe final voltage on the bulb will be in the 8 volt area with the resistor in place
For a true inrush test use the load circuit you intend to use in your final design


i used the 40R to set the current to the lamp load rated 12V / 3.5W.

Terry said:

What wattage resistor have you selected?


since the lamp needs 12V fully iam not sure of selecting a suitable power rating(since there would bedrop for the power rating chosen) for the 40R resistor.
Advice on that could be help ful.

Terry said:

is this how the lamps will be used in the intended circuit?


The circuit i have posted is just to check the life expectancy on such application. not the intended circuit.

after all what i need to work out is,
Test the reed switch sustainability and
secondly,
look for suitable measures to control the inrush current phenomena to prevent the damage to the switch.


Thanking all,
suresh.




List of 57 messages in thread
TopicAuthorDate
inrush current + suitable voltage sour      Suresh R      03/04/06 10:14      
   Inrush current of lamp      Kai Klaas      03/04/06 20:47      
      Current inrush      Hal Albach      03/05/06 06:28      
         NTC?      Jan Waclawek      03/05/06 06:45      
            Soft-start      Kai Klaas      03/05/06 08:00      
               8 reed SW parallely + 21.12A / at 12VDC      Suresh R      03/06/06 05:29      
                  Car battery???      Anders Sandström      03/06/06 05:58      
                  inrush current      Terry Lingle      03/06/06 08:20      
                  totally irrelevant      Erik Malund      03/06/06 08:58      
                  No testing needed, standardly      Kai Klaas      03/06/06 19:46      
                     replies      Suresh R      03/07/06 02:05      
                        Reply to "replies"      Kai Klaas      03/07/06 07:29      
                           the difference between "cheap" and "inex      Erik Malund      03/07/06 07:44      
                           current limit resistor      Suresh R      03/07/06 09:17      
                              are you just grasping for straws?      Erik Malund      03/07/06 09:29      
            NTC, yes      Erik Malund      03/06/06 08:54      
               Filaments      Kai Klaas      03/06/06 18:38      
                  In the days of radios for AC and DC      Erik Malund      03/07/06 06:57      
                     Thanks      Kai Klaas      03/07/06 07:03      
            resistor parallel to Switch!      Suresh R      03/11/06 04:29      
               MOSFET, constant current source?      Kai Klaas      03/11/06 07:04      
                  not for my use      Suresh R      03/11/06 09:24      
                     Ok, but...      Kai Klaas      03/11/06 10:00      
                        but i think      Suresh R      03/11/06 10:25      
                           Relays      Kai Klaas      03/11/06 10:51      
                              yes ofcourse      Suresh R      03/11/06 11:46      
                                 here we go again        Erik Malund      03/13/06 06:57      
                                    Even more!!      Kai Klaas      03/13/06 07:14      
                                       werlcome to the club      Erik Malund      03/13/06 07:18      
                                       reply      Suresh R      03/13/06 10:49      
                                          why did you not say so?      Erik Malund      03/13/06 11:15      
                                          You made a fool of us!        Kai Klaas      03/13/06 18:24      
                                             reply      Suresh R      03/14/06 03:39      
                                                That's no fun!      Kai Klaas      03/14/06 07:06      
                                                   Suresh, I hope you had fun      Erik Malund      03/14/06 07:28      
                                                   reply      Suresh R      03/14/06 10:29      
                                                      yeah 6 days later.      Erik Malund      03/14/06 10:52      
                  Hello Kai,      Suresh R      03/16/06 22:03      
                     Look at here      Kai Klaas      03/17/06 10:56      
                        Thank you very much Kai.      Suresh R      03/18/06 07:40      
                           It just strikes me      Erik Malund      03/18/06 10:20      
                              yes you are right      Suresh R      03/18/06 12:32      
                                 Reed switch problems      Hal Albach      03/18/06 19:31      
                                    Current rating?      Kai Klaas      03/20/06 19:39      
                                       I recall long ago something about a "sti      Erik Malund      03/21/06 06:47      
                                       Reed problem      Hal Albach      03/21/06 07:11      
                                          Glueing together      Kai Klaas      03/21/06 07:35      
                                             Reed problems      Hal Albach      03/21/06 09:14      
                                                reed relayrs      Terry Lingle      03/21/06 14:01      
                           power dissipation calculations?      Suresh R      03/19/06 08:12      
                              bulb voltage drop      Terry Lingle      03/19/06 10:01      
                                 Thanks      Suresh R      03/20/06 02:12      
                                 (.2*bulb resistance      Suresh R      03/24/06 05:36      
                                    The bulb      Terry Lingle      03/24/06 07:06      
                              Constant current during inrush moment      Kai Klaas      03/24/06 07:22      
                                 Thanks a lot Kai      Suresh R      03/24/06 10:12      
         Choke would be huge      Kai Klaas      03/05/06 07:28      

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