Inductance effect of bus bar cooper or terminal lugs in SPDs

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tersh

Senior Member
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new york
The longer the leads of SPDs (Surge Protector Device) to load, the larger the inductance and larger the let through voltage at the load.

I'm trying to understand (or compute) what would happen when the leads are not just wires but they pass through the bus bar or terminal lugs. Remember in whole house SPD, you install it at one of the breaker load side especially at the top breaker near the main breaker (reason is to make the shunt shorter for lower inductance and lower let thru voltage). What if (for sake of discussion), it was installed far from the top breaker or in the bottom breaker. The path or equivalent lead length would be like longer and would pass through the bus bar cooper. Would this increase the inductance?

Or imagine the whole house SPD unit leads are not made of wires but composed of bus bar cooper (or imagine you just replace the wires with bus bar cooper). How would it behave?

Playing with this online inductance calculator. I tried bigger diameter wire. The inductance actually decrease. Why does it decrease for bigger diameter wire? Does it mean for bus bar, the inductance induced is actually lesser than passing through wire of similar length or even when it pass through terminal lugs?

http://chemandy.com/calculators/round-wire-inductance-calculator.htm
 

tersh

Senior Member
Location
new york
The longer the leads of SPDs (Surge Protector Device) to load, the larger the inductance and larger the let through voltage at the load.

I'm trying to understand (or compute) what would happen when the leads are not just wires but they pass through the bus bar or terminal lugs. Remember in whole house SPD, you install it at one of the breaker load side especially at the top breaker near the main breaker (reason is to make the shunt shorter for lower inductance and lower let thru voltage). What if (for sake of discussion), it was installed far from the top breaker or in the bottom breaker. The path or equivalent lead length would be like longer and would pass through the bus bar cooper. Would this increase the inductance?

Or imagine the whole house SPD unit leads are not made of wires but composed of bus bar cooper (or imagine you just replace the wires with bus bar cooper). How would it behave?

Playing with this online inductance calculator. I tried bigger diameter wire. The inductance actually decrease. Why does it decrease for bigger diameter wire? Does it mean for bus bar, the inductance induced is actually lesser than passing through wire of similar length or even when it pass through terminal lugs?

http://chemandy.com/calculators/round-wire-inductance-calculator.htm

Or since an illustration is worth a thousand words:

HUw4Y4.jpg


https://www.schneider-electric.com/...277471/en_US/Surge protection devices SPD.pdf


My question was simply. If a meter of wire has impedance of 1 uH. What is the impedance of a meter of bus bar?
 
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