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Surge Protection Device to Low Voltage and High Current

07/27/2017 8:36 PM

I have a 100kA SPD, does this device also protect my load when low voltage other than nominal happens? I know SPD's are good in clamping TVS but will it protect my load in low voltage-high current situition?

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#1

Re: Surge Protection Device to Low Voltage & High Current

07/27/2017 11:25 PM

No. Read the datasheet and application notes regarding surge protection devices, they are not a one-device-fits-all-applications protective device. They certainly won't protect against slight over voltage or over current events.

Try reading the Dehn and Sohne lightning protection guide I have posted links to on CR4 a few times for further assistance.

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#2

Re: Surge Protection Device to Low Voltage & High Current

07/28/2017 3:33 AM

Loads don't need surge protection from low voltage!

The device that sustains the load when a low voltage is present is called an "uninterruptible power supply", usually abbreviated to the TLA: "UPS". It is fundamentally a mains-operated battery charger, a battery and an inverter with a bucket of management electronics poured all over it.

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#3

Re: Surge Protection Device to Low Voltage & High Current

07/28/2017 3:43 AM

If this is an MCCB, and 10kA is the magnetic protection, then there must be a thermal protection as well.

If the thermal protection is sized for current at maximum power, if the voltage decreases the current needs to increase in order to keep the power output, so it could give PARTIAL PROTECTION.

However, in this case there would be undervoltage coil MN more appropriated for this application.

Anyway, I must be going out of topic since this has nothing to do with lightning mentioned in answer #1.

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#4
In reply to #3

Re: Surge Protection Device to Low Voltage & High Current

07/28/2017 4:47 AM

<...if the voltage decreases the current needs to increase...> How does that happen? Could that be explained, please?

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#6
In reply to #4

Re: Surge Protection Device to Low Voltage & High Current

07/28/2017 1:37 PM

Sorry, that one got a lot more confusing than it had to be.

I meant that in (some) cases, when low impedance loads draw more than the nominal current, low coupled magnetics get higher voltage drop. Depending on the output characteristics of a power converter, if a minimum voltage is required and current is known, voltage can be calculated.

In other situations using magnetics at full specs can be achieved taking into account that magnetic components (such as transformers) have core losses (voltage dependent) and winding losses (current dependent). If your voltage is lower, you can operate at higher current while the component would not be overloaded.

Anyway, as you can see I do not know what is the exact situation so I am just guessing with random situations.

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#5

Re: Surge Protection Device to Low Voltage & High Current

07/28/2017 11:15 AM

NO! RTFM! It only is designed for one job, and one job only.

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