Switch ratings conversion from AC to DC

In summary, the conversation is discussing the use of a push-button switch rated at 3 amps @ 125vAC in a 12v DC application, specifically on a motorcycle. The question is whether the switch's AC rating can be translated to 375 watts for 60v AC or 375 watts for 12v DC. It is noted that the calculation of 375 watts for 12v DC does not seem right and the reason for the switch failing above 3 amps, regardless of voltage, is questioned. The expert explains that the switch's resistance and power dissipation determine its maximum current capacity, and using it for higher current than designed can cause it to burn the contacts. The expert also mentions that the switch cannot be
  • #1
DrAlloway
30
0
I have a push-button switch rated at
3 amps @ 125vAC

which I want to use in a 12v DC application (my motorcycle).
((on ground line under continuous use {headlight}))

Does the AC rating translate as

3 amp for 125v AC hence 375 watts

375 watts for 60v AC hence 6.25 amps

or

375 watts for 12v DC hence 31.25 amps

This calculation doesn't seem right but I was thinking that the point at which the switch will fail is determined by the Number of Electrons flowing thru the contacts at any moment in time and isn't that better represented by watts than amps??

Why would the switch fail above 3 amps no matter what the volts ?? This doesn't seem right to me either.
 
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  • #2
The switch has some resistance R. The power which is dissipated on it is RI2. If you use it for higher current than it is designed for you may just burn the contacts.

Regarding voltage - you can't use the switch for higher voltage than it is designed for - as it may spark between contacts (don't use US switches for European AC!). But you may, of course, use it for lower voltage - like in your case.
 

What is the difference between AC and DC?

AC stands for alternating current, which means that the electrical current changes direction periodically. DC stands for direct current, meaning that the electrical current flows in one direction only.

Why is there a need to convert switch ratings from AC to DC?

Switch ratings need to be converted from AC to DC because the two types of current have different properties and require different levels of voltage and current to operate safely and efficiently. Switches designed for AC may not be able to handle the higher voltage and current demands of DC, and vice versa.

How is switch rating conversion from AC to DC calculated?

The conversion from AC to DC is calculated by multiplying the AC voltage and current ratings by a conversion factor, which is typically between 1.4 and 1.7. This accounts for the differences in the peak and average values of AC and DC current.

Are there any safety considerations when converting switch ratings from AC to DC?

Yes, safety considerations are important when converting switch ratings from AC to DC. The higher voltage and current demands of DC can potentially cause arcing and damage to the switch if it is not designed to handle it. It is important to ensure that the switch being used is rated for the specific voltage and current requirements of the DC circuit.

Can any switch be converted from AC to DC?

No, not all switches can be converted from AC to DC. Switches that are specifically designed for AC or DC may not be able to handle the different requirements of the other type of current. It is important to consult the manufacturer's specifications and recommendations before attempting to convert a switch from AC to DC.

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