What exactly is the difference between a surge protector and a fuse? Can a fuse protect the electronic devices from lightning instead of surge protector?
Last Updated: 22.06.2025 01:13

“ A fuse is a device which protects the (circuit) against overload and short circuit.”
So combined with a device called a MOV or Metal-oxide-resistor, then forms the 3rd part of a “surge suppressor “.
It seems Mohan does not understand the difference between a comment and an Answer.
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If the nominal power is 4,000 watts then the current at 230volts is 16 amps.
but this device (an Inductor) … impedes the rapid changes in the current.
In schematic diagrams this is the symbol for a fuse:
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The other is “what does a “fuse” do?”
Lightning arrestor is a spark-gap device, and can be installed anywhere. What is important, is that the wire is thick enough to withstand the lightning bolt and conduct the energy away from the building.
“ … to protect building, lightning arrestor, is provided above building and directly connected to earth.”
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These devices are installed between the “hot” and “neutral” and protective ground.
(Dc diagram shown, AC is similar).
But it can get overloaded, and no longer works.
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This is where this question deviates from being a 'generic' question, and becomes more specific.
This is where the MOV conducts again, and dissipated the energy.
This is the picture of an electronic coil of wire wound around a core of magnetic material.
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Mohan forgets that a fuse is a one-time device, and needs to be replaced if it is tripped.
At least they know the answer if they wanted it.
The MOV will conduct when the voltage exceeds 50% of line voltage.
I post the exact comment here.
2024–10–11 [Victor Olarewsju Victor Olarewaju ]
This is a photo where a lightning bolt took out a home's complete mains distribution box, and a lot of electronic gear as well.
This is a high voltage low current spike that comes down the line because of the power poles being struck, and the voltage suppressors activating on the primary side of the transformer.
2024–10–11 [Bobby Sanchez Bobby Sanchez ].
He then describes the function of a fuse.
There is no harm in having the surge suppressor along with the fuse in the circuit. The fuse will not open up until the current melts the link. This will take time, and in the interim, that jolt will get transmitted into the power supplies.
Now when you have a certain ac resistance, then a current flows in a loop.
the problem then depends on "how fast does the fuse operate?".
(There is no concept of polarity, in the loop because the current changes direction 100 to 120 times a second (power frequency).
The third is lightning and “how it gets conducted into a home.”
“ A surge suppressor is the one which is connected at the input supply so that when there is a sudden change voltage it bypasses thereby protecting the (circuit) and electronic components”
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When the current is 200% of the rated value , it will “go open” (the link metal melts) and protect the device.
Barnstars:
so, what happens?
One is “what exactly is in a ‘surge protector’ ? ”
These are simplified answers to the original question, and does not change anything I wrote above.
What does a fuse do?
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A circuit breaker is similar, but is resettable.
What is lightning?
2024–09–27 [ Mohan Rajaratnam Mohan Rajaratnam ] . Thinks you can get free electricity from nothing : Mohan Rajaratnam's answer to Is it possible to generate free electricity at home using a magnet or other low-cost methods? If so, how does it work?
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2024–10–16 [ OO OLAOYE OYEBODE ]
OK, this is Mohan Rajaratnam’s definition of a Surge suppressor.
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Edit 2024–10.
For this case there are devices called Metal oxide varistors (MOV).
It also is a device that limits the change in current flow.
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Is the question then , "why buy a surge supressor, if the fuse alone protects the electronic circuits from a lightning bolt?".
A fuse is a non-resetable over current circuit protector.
So, the voltage could go up to 500 volts, and the fuse will not open up.
Would individual surge supressors have save this equipment? most likely, since the surge supressor would take the jolt instead of the electronic components.
An AC voltage/ current source, and an ac inductive load.
But… the neutral is now “floating” because of the 1 ohm resistance.
but I think this circuit , shows a few more pieces.
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But during the surge, the fuse will not blow if it is a longer duration and lower value )10 to 50%).
The bolt then partially travels down the line to your home.
At the secondary, it is 1000 times less.)turns ratio). If it gets hit with a 100,000 volt bolt of lightning then the voltage arrestors conduct and clamp the voltage down to line voltage, ( but a small amount leaks down the line). This is the problem.
He then describes Rainy Season and Lightning.
2024–10–00 [ Ammar Mahdi ] Ammar Mahdi
so, the loop of wire then, when put together with another loop reduces the ‘noise’ on a power line.
[old diagram got deleted by accident]
Can the fuse protect the electronic devices from lightning instead of a surge protector.
[image of Common-mode choke]
Here is a simplified AC power diagram.
Once the voltage goes over 0.0650 volts, then this fact can be used to amplify the difference, and turn the circuit breaker off , furthur down the line. Essentially that is what a RCD/GFCI does, it compares the incoming current, to the outgoing current, and if the difference between the two currents is over 5mA, then it trips the circuit breaker.
He then asserts :
2024–10–14 [Omar Gharbi Omar Gharbi ]
Because the load is inductive, the current lags the voltage.(by a bit).
Upvotes:
what exactly is a ‘surge’ protector?
One
This one hit behind the barn.
This is 'the assistant's answer'
There are two important concepts here.
First Sentence:
And this is the problem alone. Is the power supply in the equipmemt designed with a lightning strike in mind? Some yes, others, no.
a photo is worth a thousand words.
2024–10–10[John johnson John Johnson ]
So, it’s possible that these devices from Trip Lite have addition suppression devices, these ones seem to be sturdy.
This is an electronic circuit designed to clamp voltages so that the Voltage Potential that appears at the outlet is never going to exceed the nominal value.
There are three different concepts here that are getting confused.
Fuses, on their own, then operate much slower than the MOV variable resistance, during the lightning strike.
P = e* I, so since I is 16 amps, then the voltage dropped is 1/16 volt or 0.0650 volts.
It’s been three xxx five werks, and there has been no response to my follow on query on his Commment to my answer.
This device then solves the entire problem.
At one ohm, the resistor has a maximum of 1 watt power.