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I am referring the Schneider's EasyPact Circuit Breakers (but I do believe that my question also applies to Circuit Breakers in general)

Let be EZC250F3200 model our subject for today. By looking at its datasheet, we can see that:

enter image description here


The definition of \$U_e\$ from IEC 60947-2 standard is:

\$U_e\$ is generally stated as the voltage between two phases

which leads me to believe that the term "Rated Operational Voltage" simply means that it is the Circuit Breaker's voltage at which it is designed to perform.

Going back to my question, will there be any negative effects/impacts on Circuit Breaker's

  • internal parts/functions
  • terminals
  • or even safety of operation

if I install the Circuit Breaker to the system voltage (230 V, 60 Hz, 3-phase, No Line-to-Neutral loads) that is much lower compared to its "Rated Operational Voltage" \$U_e\$ (550 V AC)?

I hope that your answers will be based on a reference book, technical paper, or standard, or perhaps you are working on Circuit Breaker production. Anyone can simply say that there will be no negative effects as long as the system voltage doesn't exceed the rated operational voltage but I want a piece of evidence that can give me assurance. I really appreciate your effort to answer and I am looking forward to learning from you.

PS: I don't know if it matters or not, but the circuit on which the EZC250F3200 will be installed is mainly composed of various small motor loads and heating elements.

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    \$\begingroup\$ These are the type of questions you should ask the manufacturer. They designed it and they give a warranty. \$\endgroup\$
    – Kartman
    Aug 2, 2021 at 0:17
  • \$\begingroup\$ "I hope that your answers will be based on a reference book, technical paper, or standard, ..." Unlikely, I'd think. Most of us would consider it fairly obvious and I've never seen a lower voltage limit. Why would there be? \$\endgroup\$
    – Transistor
    Aug 2, 2021 at 12:26
  • \$\begingroup\$ nicy12 - I've updated my answer to cite the manufacturer's datasheet which hopefully provides the traceable reference that you are wanting. The datasheet specifies a number of voltages less than rated max and gives rated current and breakable-current and conditions. It's an impressive breaker. \$\endgroup\$
    – Russell McMahon
    Aug 2, 2021 at 12:43
  • \$\begingroup\$ @Transistor re "why would they be" --> lower voltage limit for any breaker will usually not exist, as you indicate. It's conceivable that a breaker could use supply voltage or eartth or neutral reference to perform some function. This is not the norm but I'd suggest caution in thinking that it is never done. In this case a look at the data sheet shows it is a 3 pole breaker with 3 seperate inputs and 3 outputs and can specifically be operated in single pole mode so it does not depend on any external reference - as you'd expect in most cases (as you said). \$\endgroup\$
    – Russell McMahon
    Aug 2, 2021 at 12:47

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Rated voltage is properly read as "Maximum" operating voltage".

It is constrained by the ability to break an arc while otherwise operating at rated (= maximum permissible) current. Fault current may be say 100 times rated operating current.

Tripping is invoked by excess current and is very largely voltage independent.


The datasheet for the EZC250F3200 breaker is here

As you noted, Ue, the rated opertational voltage is 550 VAC at 50/60 Hz.

However, the rated fault current breaking capacity (between 5,000 and 25,000 amps) under a range of consitions is specified. All of these are of necessity no higher than the rated voltage and current capacities and most are lower.

For AC voltages of 110 220 277 380 440 ... are mentioned.
For DC voltages of 125 and 250 VDC are mentioned.

The strong implication is that any intermediate voltages are also acceptable - but the standard voltages given allow specific current and breakable-current to be provided.
From the cited datasheet.

enter image description here

Installation guide here

I note the droll warning "Failure to follow these instructions will result in death or serious injury."

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