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?
12.06.2025 05:42

He then describes the function of a fuse.
This is where this question deviates from being a 'generic' question, and becomes more specific.
He then asserts :
It seems Mohan does not understand the difference between a comment and an Answer.
Upvotes:
A fuse is a non-resetable over current circuit protector.
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so, what happens?
what exactly is a ‘surge’ protector?
Now when you have a certain ac resistance, then a current flows in a loop.
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First Sentence:
He then describes Rainy Season and Lightning.
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Here is a simplified AC power diagram.
And this is the problem alone. Is the power supply in the equipmemt designed with a lightning strike in mind? Some yes, others, no.
So combined with a device called a MOV or Metal-oxide-resistor, then forms the 3rd part of a “surge suppressor “.
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The bolt then partially travels down the line to your home.
[old diagram got deleted by accident]
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.
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a photo is worth a thousand words.
When the current is 200% of the rated value , it will “go open” (the link metal melts) and protect the device.
A circuit breaker is similar, but is resettable.
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What does a fuse do?
so, the loop of wire then, when put together with another loop reduces the ‘noise’ on a power line.
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(Dc diagram shown, AC is similar).
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.
Is the question then , "why buy a surge supressor, if the fuse alone protects the electronic circuits from a lightning bolt?".
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This is where the MOV conducts again, and dissipated the energy.
Because the load is inductive, the current lags the voltage.(by a bit).
If the nominal power is 4,000 watts then the current at 230volts is 16 amps.
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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?
But it can get overloaded, and no longer works.
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.
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2024–10–10[John johnson John Johnson ]
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.
But… the neutral is now “floating” because of the 1 ohm resistance.
The other is “what does a “fuse” do?”
2024–10–16 [ OO OLAOYE OYEBODE ]
What is lightning?
Barnstars:
At least they know the answer if they wanted it.
An AC voltage/ current source, and an ac inductive load.
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This device then solves the entire problem.
“ 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”
The MOV will conduct when the voltage exceeds 50% of line voltage.
“ A fuse is a device which protects the (circuit) against overload and short circuit.”
This one hit behind the barn.
These devices are installed between the “hot” and “neutral” and protective ground.
One is “what exactly is in a ‘surge protector’ ? ”
OK, this is Mohan Rajaratnam’s definition of a Surge suppressor.
Fuses, on their own, then operate much slower than the MOV variable resistance, during the lightning strike.
This is the picture of an electronic coil of wire wound around a core of magnetic material.
2024–10–14 [Omar Gharbi Omar Gharbi ]
“ … to protect building, lightning arrestor, is provided above building and directly connected to earth.”
There are three different concepts here that are getting confused.
(There is no concept of polarity, in the loop because the current changes direction 100 to 120 times a second (power frequency).
Edit 2024–10.
The third is lightning and “how it gets conducted into a home.”
P = e* I, so since I is 16 amps, then the voltage dropped is 1/16 volt or 0.0650 volts.
but this device (an Inductor) … impedes the rapid changes in the current.
It also is a device that limits the change in current flow.
For this case there are devices called Metal oxide varistors (MOV).
At one ohm, the resistor has a maximum of 1 watt power.
Can the fuse protect the electronic devices from lightning instead of a surge protector.
2024–10–11 [Victor Olarewsju Victor Olarewaju ]
the problem then depends on "how fast does the fuse operate?".
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.
but I think this circuit , shows a few more pieces.
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 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 'the assistant's answer'
So, the voltage could go up to 500 volts, and the fuse will not open up.
2024–10–00 [ Ammar Mahdi ] Ammar Mahdi
[image of Common-mode choke]
But during the surge, the fuse will not blow if it is a longer duration and lower value )10 to 50%).
I post the exact comment here.
There are two important concepts here.
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.
So, it’s possible that these devices from Trip Lite have addition suppression devices, these ones seem to be sturdy.
2024–10–11 [Bobby Sanchez Bobby Sanchez ].
Would individual surge supressors have save this equipment? most likely, since the surge supressor would take the jolt instead of the electronic components.
These are simplified answers to the original question, and does not change anything I wrote above.
Mohan forgets that a fuse is a one-time device, and needs to be replaced if it is tripped.
In schematic diagrams this is the symbol for a fuse:
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