Questions tagged [circuit-breaker]

An automatically operated electrical switch designed to protect an electrical circuit.

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Safety of a polarized DC breaker between the battery and the inverter

DC breakers use a magnet to blow the arc into the quenching channel. If the current is flowing in the wrong directly, the arc is pulled into the guts of the breaker and can cause the arc to be ...
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Polarized DC breaker between the battery and the inverter [closed]

I'm setting up a 5kW off grid solar system and planning to install a 125A polarized Dc breaker in between the 5kWh lifepo4 battery and the MPPT inverter. I heard that a polarized breaker isn't ...
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Main breaker not tripping [migrated]

We just connected the power company's meter to our new construction and got an immediate humming sound which the meter technician said should not happen. We later found that one of our electrical ...
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Are 3P+N circuit breakers designed to make neutral first and break neutral last?

Consider a CEE 60309 connector, 3P + N + PE. The pins have equal length, but the conductive sleeve matching up with the pins dont have the same length; and of particular interest is that the neutral ...
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Safety check - Is this Amazon PV combiner box labeled wrong? 15A Vs 32A - 500V vs 1000V

I'm currently working on a solar circuit. I wanted to protect my internal systems from my panels in the event of a surge. I purchased a PV combiner box from Amazon - link to product. It claims to be a ...
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Single vs two pole breakers - Single phase loads on IT power with distributed neutral

Are two-pole breakers required on single-phase 230 V loads when connected to a 3-phase supply with IT earthing system (with distributed neutral) in Germany? Where in the standards is this requirement ...
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How exactly does a breaker finder work?

I've used a breaker finder for a while now, and I'm curious as to how it actually works. The only explanations I can find online are layman explanations (e.g. it sends a signal up from the outlet to ...
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4 answers
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Why do Americans use fuses and not differentials and breakers like Europeans do?

I recently moved to North America, and I was wondering why the houses here seem to be protected by fuses rather than breakers and differential switches like we have in France for example. It would ...
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Can a lower gauge jumper be connected to a high amperage circuit as long as it is going to an appropriate sized breaker?

The 14 AWG wire is connected to an appropriate sized circuit breaker to prevent that run of wire from drawing too many amps; however, my concerns would be that the 2/0 cable being in such close ...
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Breaker with alarm

I am thinking about a theft alarm for an HVAC condenser. The condenser is installed outside and subject to burglary. I think a viable approach is detecting when it is detached from power. The HVAC ...
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Charging capacitor trips breaker

I am designing a circuit to drive a DC motor from rectified mains voltage. For that, I have added a 1200uF capacitor. My problem is that this circuit is supposed to work on a user's home power plug, ...
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Three-phase circuit breaker trip current

If a three-phase circuit breaker is specified as, for example, a 32 A breaker, does this mean the breaker will trip when the current in a single phase exceeds 32 A, or when the total current of all ...
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What will happen if I use RCBO where there is no neutral in the system?

I need some help. Could you please go through the scenario and try to answer my query below? This system is installed in a ship where there is no neutral connection available. A 440V/220V step-down ...
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3 Phase breaker - Current Limit

I have a simple question... If I have this 3 Phase breaker: That means its current limit is 20A right? My question is, is it limit for the whole breaker or limit for every phase separately?... What ...
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16 A mains breaker and heat

So I got curious and could not find any good information on high breaker load over an extended period. In my home (in EU, 240V) there is a breaker which is rated for 16 A. If 16 A is drawn for hours ...
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Is it necessary to add rotary handles with each incoming and outgoing MCCBs in a Form 3B type LT switchgear panels?

As far as I understand, mainly the function of a rotary handle is a locking function. So in a form 3B type panel, where each breaker is kept in a separate compartments, will there be a problem if ...
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2 answers
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The home single phase differential switch cuts whatever I did [closed]

I have a 30 mA sensitivity differential switch which cuts each time I lift the power switch even if the circuit breakers for the sockets and the lighting are off (even if all the circuit breakers on ...
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CBE Schematic and Wiring

I'm in the process of installing a circuit breaker between a power supply and an HMI device, but have some uncertainty when it comes to illuminating the rocker switch. The part number is TA35-...
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1 answer
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How to fix this ABB MS325 circuit breaker?

I have couple broken training bench circuit breakers. The broken part is the manual switch. I uninstalled one and tried to open it. I was able to open the back side which contains metal connectors ...
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Let-through current of MCB

I'm wondering what's the reason of creating the let-through current diagrams for fuses and not for MCB's. Even more curious I'm, because one of largest manufacturers is providing the let-trough ...
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Why can't the circuit breaker interrupt this circuit?

I have a 3-phase input in my home. There is 127 V between any of the phases and neutral, and 220 V between any pair of phases. The electrical appliances have 127 V, and the wirings are such that the ...
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Will there be any negative effects if I install the Circuit Breaker to the system voltage lower than its "Rated Operational Voltage"?

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 ...
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2P circuit breaker, Ground wiring

i need to test some outlets and im using a 25A 2P circuit breaker, from what i researched i need to connect neutral and hot to the circuit breaker and from there to the outlet. My question is, do I ...
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RCCB - Residual Current Circuit Breakers (FID) are randomly blowing

We have a problem with FIDS (RCCB) randomly blowing, different cabinets, not connected at all. Trying to solve it for few months now with army of electricians... So far, we have measured 4000A ...
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What Siemens part can I replace this Lovato part with? [closed]

Original part: Lovato Circuit Breaker -- 10A, 2-Pole, C-curve -- https://www.solutionsdirectonline.com/lovato-miniature-circuit-breaker-10a-2-poles-p1mb2pc10 Official page: https://www.lovatoelectric....
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Sizing Circuit breaker, and I believe my calculation is wrong. Can anyone help me out

I am looking at a 3Amp rated circuit breaker, and the datasheet given below of the derating factor, and trip time in second. The average office temperature is 71F. Cable Current rating = Rated ...
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2 answers
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DC Parallel Breakers

I need a single-pole circuit breaker for a 200A, 48V DC battery bank powering a solar inverter. The batteries are LiFePO4 and capable of large short-circuit currents on the order of 10 to 15 kA. ...
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How do I cut power inside a main panel when there's no service disconnect present? [closed]

I am trying to install a 50A circuit breaker for a 14-50 outlet. I'd like to put that breaker in the main panel of the house. Looking at my panel I cannot figure out how to cut power to the whole ...
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9 votes
6 answers
3k views

Could an uninterruptible power supply for energy intensive appliances balance the power draw and help my breaker stop tripping? [closed]

Non-engineer here. Well, not the electrical kind. About once a week the breaker to my office (read: gamer cave) trips. I just noticed that our 70 inch TV, 2 x Echo Studios, etc. in the living room on ...
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Grounding and protecting 12V Inverter

I am always surprised when researching online for a topic for a few hours does not bring solid responses. This is one of such situations. I am in the process to provide AC power to a remote small ...
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Can an Adjustable Circuit Breaker be adjusted while Energized?

For a Low Voltage Circuit Breaker, such as the Legrand DPX3 630, 3x400A, 36kA, 400V, we have adjustment dials to change the properties of the magnetic (Magnetic adjustable from 5 to 10 In) and or ...
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battery low voltage cut off breaker (manually reset)

First off, I am aware that premade devices like this exist however I have been unable to find any that fit my exact needs which are as follows. 0 power draw when in the off state Minimal voltage drop ...
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17 votes
8 answers
4k views

Do circuit breakers trip on Apparent or True Power?

The thermal and magnetic protection for AC circuit breakers take into account both the timing and the magnitude of the AC current passing through. Does a standard circuit breaker trip on the current ...
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When is a fuse used in tandem with a breaker/MCB?

I have observed that at the input (supply side) of some electrical units, only MCB is used for overcurrent protection; whereas in other units, a fuse is used as well as MCB at the input side. Why and ...
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8 votes
2 answers
2k views

Why does a circuit breaker voltage rating differ between AC and DC?

I'm looking at circuit breakers from Allen Bradley's 1492 series: (https://configurator.rockwellautomation.com/api/Doc/1492-SPM%20Specifications.pdf) For each circuit breaker, it lists a AC and DC ...
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20 amp to a 40 amp circuit [closed]

On the back of my house is the breaker box. It has an open 40AMP fuse (not connected to anything any more). There is also a 20AMP fuse connected to my shed. When the shed was originally built, it was ...
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Why does adding one more extension cable turn the MCB on again?

I found a strange phenomena when I tried to use a metal cutter that consumes about 2000 watt. See the following illustration. If I just use one extension cable, the MCB will trip when I turn on the ...
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3 answers
279 views

Why can't circuit breakers close across a large phase angle difference?

In power systems I understand that breakers have mechanisms preventing their closing if they detect the phase angle (and voltage) across them to be too large. This is usually called a 'sync check'. ...
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1 answer
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Connecting a 120V/30A variac to a 240V circuit

I have a variac rated for a maximum output of 30A. The problem is it takes 120V on the input and all of my 120V circuits are 15A, as expected. I unfortunately cannot just add an additional 30A circuit ...
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4 answers
151 views

Is there a device to prevent a main circuit breaker from tripping and give an added layer of protection?

I would like to install some additional appliances in a room that already has a couple of heavy equipment machines running in it. These are sensitive machines, so instead of having the main circuit ...
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1 answer
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How to create a break away to cut the board

I am not a expert with Eagle 9.6 but I created a nice PCB. A friend of my is going to assembly the part with a pick and place machine. He asked me to enlarge my PCB to be able to fix the board and ...
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3 votes
2 answers
144 views

Fault current indicator - what should I do?

Part of the power plugs in my flat stopped working this morning. I checked the breakers box and one of the breakers was in OFF position, with a yellow indicator. After checking the producer's website, ...
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33 votes
10 answers
17k views

What causes a fuse to blow, the current or the power?

Fuses and circuit breakers are often specified at a certain current they will 'blow'. Increasing the current will also increase the power. So if a fuse is rated for 12V DC and 20 A, this would be ...
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Are breakers polarized?

I would like to know if a circuit breaker is polarized if it looks like this: I would also like to know how I can manually turn off these breakers and how to reset them.
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Can I avoid tripping my breakers with an superinductor?

I was thinking about creating a circuit with a large inductor to avoid tripping my breakers when I turn on an iron. When I use the iron, if I slowly start it with minimum heat and gradually increase ...
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2 answers
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How do TVSS and Circuit Breakers (thermal-magnetic) interact with each-other?

In EU you can find thermal-magnetic circuit breakers all other the places in buildings and it's not uncommon to have daisy chains of them (meaning a main panel will have one, which is connected to ...
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2 votes
1 answer
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Why location of CT is different for the two Circuit breakers in same substation layout?

This is a schematic diagram of a traction substation. In this traction substation protection system schematic diagram, at point marked 'A', CT is located after the 25kV CB. However, at point marked 'B'...
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What does this switch do?

Also, what is that circuit element symbol (an arrow leaving a rectangle) called, in the diagram next to the switch?
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1 answer
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Can I replace a 32 A switch with a 32 A MCB?

A switch for a water heater in my apartment is broken (image attached). It is an "Anchor Roma 32 Amp 1-Way Switch with indicator". Can I replace it with this or this switch? Would the installation ...
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2 answers
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3-Pole Circuit Breaker with GPIO

I'm starting a small project involving 3-pole circuit breakers and 3-ph motors. There's this custom built machine with multiple 3-ph motors, each connected to circuit breakers. The purpose of the ...
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