Relay Wattage Calculation

Thread Starter

Ally Cat

Joined Mar 28, 2016
78
If we have a HE12-1A69-02 from Standex Electronics. The point is that rating is 50 W and can do up to 10,000 Volts. If used a voltage of 5 kV for a load greater than 10 mA the power would be exceeded. Or since the power of the relay not really apply cause the voltage being dispensed across the relay is essentially zero when closed. If this is true does the maximum current draw across the load is limited not by the 10 mA limited by the power calculation but by the max current draw since the relay is acting as a wire. Thus we can use the maximum current of the relay.
 

-live wire-

Joined Dec 22, 2017
922
If we have a HE12-1A69-02 from Standex Electronics. The point is that rating is 50 W and can do up to 10,000 Volts. If used a voltage of 5 kV for a load greater than 10 mA the power would be exceeded. Or since the power of the relay not really apply cause the voltage being dispensed across the relay is essentially zero when closed. If this is true does the maximum current draw across the load is limited not by the 10 mA limited by the power calculation but by the max current draw since the relay is acting as a wire. Thus we can use the maximum current of the relay.
It seems strange to rate a relay like that. Are you sure 50W isn't the maximum power dissapation? I can't really imagine an electromechanical relay that can handle 10kV but not more than 10mA. If it's 50W dissipated, then the maximum current would be 50W/R, where R is the resistance of the contacts. This rating doesn't make sense. 6mA at 10kV is too much, but 50A at 1V is okay?
 

ebp

Joined Feb 8, 2018
2,332
It is somewhat unusual for a contact to be rated that way, but by doing so the manufacturer assures that the power the contacts are subjected to at closing and opening, when there is both current through them and voltage across them because they pass through a high resistance state, is tolerable in terms of contact "wear" and longevity. Gold plated contacts intended for low-level use are often rated for maximum volt-ampere (VA) product. As I recall, 0.4 VA is common for manual switches with such contacts.

With contacts fully mated with full pressure, high current in a high voltage circuit would be OK, but expect your reed relay to be destroyed completely and possibly violently if it should ever open under such circumstances.
 
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