OMRON Micro-switch characteristics

M

Thread Starter

Mario de Sousa

Hello all,

I have been lurking on this list for quite some time now, and given the general level of knowledge here, It ought you might be able to
help me on this seemingly simple problem:

Summary:
The data sheets and the labeling on the component do not match. The suppliers don't seem to understand anything of what they are saying.

Equip. Ref:
OMRON microswitch V-165-1C5

Problem description:
The data sheets of this switch, as given to us by OMRON in Portugal, give the following maximum load currents:
16 A resistive load
10 A inductive load (0.4 power factor)
2 A incandescent lamp (taking into account that initial surge current may be up to 10xnominal current)
3 A electrical motor (taking into account that initial surge current may be up to 6xnominal current)
The problem is that on the microswitch we find the following label:
16 (4) A
Both OMRON in Portugal, and their suppliers (Netherlands ??) don't seem to understand anything about the subject, or if they do,
seem to be trying to pull wool over our eyes. Their answer is that the current in parentisis is the maximum current of an electrical motor load, and that the microswitch has been slightly changed, and that it therefore can now handle 4 A instead of the 3 A stated on the data-sheet, but it is better to stick to the 3 A limit, just in
case...!!!

Questions:
1) To the best of my knowledge, the number in parentisis is the maximum current for inductive loads. Why is this different from the data sheet?
What is the correct value for this microswitch?
2) In what standard is the labeling of maximum currents defined?
3) Any sugestions as to alternative suppliers? We are buying these by the thousands. Current handling capacity must be at least 10 (6) A, with
similar mechanical housing and characteristics.

Background for the curious:
This microswitch is being used in the manufacturing of an integrated liquid level sensor, and needs to be able to withstand 10 (6) A.

P.S. My usual mail handler has gone down, and I seem to have stopped receiving the alist mails. Could you please send me ([email protected]) a copy of your anwsers directly?
 
J

Johan Bengtsson

What usually kills a switch, especially when connected to an inductive load, is when the switch is opened, not when it is closed. This means that if you connect a motor (inductive load with a high inrush current) and NOT open the switch until the motor have reached it's
operating speed (ie the current is at a normal level) the motor will have a "killing" potential as any other inductive load. If you however open DURING the motor speed up (ie at high motor inrush
current) the "killing" potential is a LOT higher.
The power factor is higher for most normal induction motors during normal operation and that means they will not kill the switch as bad as the
inductive line below (power factor 0.4). An unloaded motor does have a lower power factor than a loaded, but also needs less current.

My favorite supplier is a Swedish company called elfa, http://www.elfa.se/en if that may help you


/Johan Bengtsson

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P&L, the Academy of Automation
Box 252, S-281 23 H{ssleholm SWEDEN
Tel: +46 451 49 460, Fax: +46 451 89 833
E-mail: [email protected].se
Internet: http://www.pol.se/
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