they all have an override although some are better hidden than others.
depending on design and rating of the feed (expressed in calories per area), accessing may require proper PPE gear to protect user against both electrocution and arc-flash. i was never huge fan of the PPE but one has be safe or risk being fried or blown to pieces.
i was never too concerned with electrocution because i trust my own skill and tools. but the arc-flash is much more dangerous because it can happen even when it was triggered by someone away, like in another part of the building.

for educational video with lots of destroyed dummies see this

 

But generally, service personnel with knowledge of the machine will usually know the location of the (enclosure door et-al) micro-switch and override it for maintenance purposes.
When used, it is usually to protect the uninitiated of being electrocuted, particularly when such as 440v (Canada 600v) is present.
I have never seen it as an issue when servicing a machine.

You are fortunate indeed! Power off has frequently been a royal pain. T\Needing to watch PLC module lights to see if a limit switch signal is arriving, and looking at outputs to see if a solenoid valve signal is being switched on. Tasks that are simple and far away from the 480 volts. And people who are in a panic because the door is open with the power on. Even the line workers are smart enough to not reach in and touch things. In fact, even the jitney drivers have figured that out. Only the forman seldom has a clue.

 

You are fortunate indeed! Power off has frequently been a royal pain.. And people who are in a panic because the door is open with the power on. Even the line workers are smart enough to not reach in and touch things. In fact, even the jitney drivers have figured that out.

It comes down to who designed and built the panel or the MTB, fortunately I have not come across it all that much, but either way, no big deal.

 

It comes down to who designed and built the panel or the MTB, fortunately I have not come across it all that much, but either way, no big deal.

What is an "MTB" ???? Undefined acronyms are ALWAYS A PAIN, "MCB" was really confusing because it is normally taken to translate to "Main Circuit Breaker. And the typical branch-feed breakers are by no means miniature. They are accurately called "branch feed" breakers.
Certainly I will be called for being picky about meanings and undefined acronyms, but engineering is built at least partly on accurate communication. So those who assign different meanings to common words should not expect to get correct answers to their questions.. Meanings of words usually do matter quite a lot .
Would one really describe the function of an electrical distribution panel as "big circuit breaker and little circuit breakers, defining each by size with no reference to the application or function?? Main circuit breaker and branch circuit breakers is far more descriptive..

 

OFF-TOPIC WARNING: DO NOT READ IF YOU ARE ONLY INTERESTED IN STRICTLY THREAD CONTENT​

Hello, @meowsoft! Good to see you, it’s been a long time—I hope all is well with you.

 

What is an "MTB" ???? Undefined acronyms are ALWAYS A PAIN, "MCB" was really confusing because it is normally taken to translate to "Main Circuit Breaker.

MTB = Machine Tool Builder. AKA OEM = Original Equipment Manufacturer
MCB = Miniature Circuit Breaker In domestic situations, Although also used as "Main Circuit Breaker" in industrial equipment.

 

Most residential panels have a single MAIN breaker and several branch breakers. And I always refer to the main as the main, and never refer to breakers by their physical size.
And thanks for the MTB definition. OEM I was aware of, being one for several years.

 

OFF-TOPIC WARNING: DO NOT READ IF YOU ARE ONLY INTERESTED IN STRICTLY THREAD CONTENT​

Hello, @meowsoft! Good to see you, it’s been a long time—I hope all is well with you.

Hello... nice to see you too...

 

Returning to the original question as to any benefit from using series fuse and circuit breaker, the answer is that it depends very much on both the specific equipment and the application.
In some parts of the world published specifications are fictional and actual device performance unknown.
Actual device performance requirement specifications, such as response time versus current vary widely with the application, and so the designer must understand the application requirements to select the correct device. Without any additional information about the load requirements there can be no specific answer.
Normally the branch circuit protection is selected to protect the branch circuit wiring from overload damage.

 

The purpose of a fuse or an MCB (miniature circuit breaker) is to keep the wiring from burning due to an overload or short-circuit condition.

The term 'overload' refers to the condition in which the current carrying capacity of the cable is exceeded.

The term 'short-circuit' refers to the condition in which the wire closes the circuit without any load. In other words, the wire forms a closed circuit across the source terminals, leading to an abnormally high current, known as the short-circuit current.

In both the fault conditions, a fuse will melt to break the circuit whereas an MCB will 'trip' to open it.

It's easy to switch on the MCB after clearing the fault, in contrast to the expenditure / effort involved in replacing a fuse.

Using an MCB and a fuse in series would be an exercise in futility.

Nandu.