Saturday 11 February 2017

Relay datasheet question


In the datasheet, they wrote:



Rated frequency of operation with / without load 6 / 1200 min-1


What's the signification of this line ?


When they talk about Mechanical endurance cycle, is it open to close or open to close to open



Answer



They say



  • Max. switching rate at rated- / minimum load - 6 min-1 / 1200 min -1


First establish what "rated load" and "minimum load" mean


(1) What does "rated load" mean ?



There are 12A and 16A versions.
Considering 12A version.


Max rated switching current is 12 A Switchable voltage = 250 VAC or 440 VAC .
Max switched VA = 3000
SO at 250 VAC max switched i = 3000/250 = 12A as expected.
But at 440 VAC max amps = 3000/440 = 6.8A
ie it can be used at 12A at 250 VAc but must be derated to 6,8A if 440 VAC is used.


So raed load = 12A at 250 VAc or 6.8A ay=t 440 VAC.


(2) What does "minimum load" mean?


Some relays have a minimum rated switched current for eg contact wetting purposes. I could not see any minimum spec.

Assume that "minimum load" = no load.




Then -


(3) So


" - Max. switching rate at rated- / minimum load - 6 min-1 / 1200 min -1" means




  • When loaded at 250 VAC, 12A OR at 440 VAc, 6.8A it may be switched at a maximum rate of "6 min-1" = 6 times per minute = not more than once every 10 seconds.





  • When loaded at zero amps - say perhaps 250 VAC present or 440 VAC present but no load then max switching rate = "1200 min-1"= 1200 times per minute = 20 times per second !!!




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