7 guidelines to select correctly rated circuit breaker _ eep

7212019 7 Guidelines to Select Correctly Rated Circuit Breaker _ EEP

httpslidepdfcomreaderfull7-guidelines-to-select-correctly-rated-circuit-breaker-eep 18

1272015 7 Guidelines To Select Correctly Rated Circuit Breaker | EEP

httpelectrical-engineering-portalcom7-guidelines-to-select-correctly-rated-circuit-breaker 18

7 Guidelines To Select Correctly Rated Circuit Breaker

7 Tips To Select Correctly Rated Circuit Breaker (on photo Low voltage molded case circuit breaker type COMPA CT

NSX 100H credit Edvard Csanyi)

Selection of rated circuit breaker

SHARE





The general procedure for the selection of correctly rated circuit breaker follows the following scheme of seven

major questions you should answer

1

2

3

45

6

7

1 What is the task of the branch circuit or feeder

Will it be used for the protection of connecting leads protection of installation group-protection or motor protection

Select the appropriate circuit breaker type with or without the thermal overload protection Decide which type of

protective characteristic (cable or motor protection)

2 Which rated current setting rangeDo the setting ranges of the thermal and the magnetic release cover the requirements of the particular application

(protection of transformer or generator)

What is the task of the branch circuit or feeder

Which rated current setting range

Breakingmaking capacities rated operational voltage

Any special requirementsWhich type of co-ordination

What is the mode of mounting

Cross-section of the connecting wirecable

Go back to CB Selection Tips uarr





The setting ranges of the various sizes of circuit breakers are

overlapping The same current settings may be partly covered by

more than one size of circuit breakers (as for example 80 A

setting can be covered by two or more CB sizes 100A or 125A)

The following features depend on the size of the circuit breakers

Accessories (as for example types and numbers of auxiliary contacts)

Mode of operation (toggle or rotating handle)

Mode of mounting (snap-on or screw mounting) or

The electrical characteristics (breaking capacity selectivity etc)

3 Breaking making capacities rated operational voltage

Where is the of the circuit breaker

What is the expected magnitude of the prospective short-circuit current at that location

Is a lower makingbreaking capacity acceptable (appreciable reduction of the short-circuit current due to long

connecting leads or due to other short circuit protective devices connected upstream)

Is the breaking capacity reduced due to higher rated operational voltage (as for example gt400 V)

Does it indicate a selection on the basis of Icu (rated ultimate short-circuit breaking capacity reduced functional

capability after the interruption of a short-circuit) or on the basis of Ics (rated service short-circuit breaking

capacity full functional capability after the interruption of the short-circuit)With the help of an efficient group-protection can smaller and less expensive circuit breakers be utilised


point of installation





Not sure what are the breaking and making capacity Learn here

4 Any special requirements

Must reduction factors for the rated current be taken into account due to ambient air temperature (gt40hellip60 deg)

altitude of the site of installation (gt2000 m above msl) higher supply frequency (gt400 Hz)

5 Which type of co-ordination

Selection of the downstream contactor in accordance with the type of co-ordination type ldquo1rdquo or type ldquo2rdquo

6 What is the mode of mounting

Deciding factor for the supportingadapter plates of the (suitability for the selected type of

circuit breaker)

Compact NSX circuit breakers installed on mounting plate (photo credit Edvard Csanyi)




modular mounting system






7 Cross-section of theconnectingwirecable

The cross-section of the

connecting

leads to the

motors are to

be selected on

the basis of

the current

setting of the

of the circuit breaker Eventually the maximum permissible length of the connection is to be

considered (shock hazard due to touch potential in the case of a short-circuit)

Circuit breaker rating plate

Standardized characteristics indicated on the rating plate of Compact NSX circuit breaker

thermal overload release






Compact NSX rating plate

1 Type of device ndash frame size and breaking capacity class

2 Ui ndash rated insulation voltage

3 Uimp ndash rated impulse withstand voltage

4 Ics ndash service breaking capacity

5 Icu ndash ultimate breaking capacity for various values of the rated operational voltage Ue

6 Ue ndash operational voltage

7 Colour label ndash indicating the breaking capacity class

8 Circuit breaker-disconnector symbol

9 Reference standard





Share with engineers

10 Main standards with which the device complies

Note

When the circuit breaker is equipped with an extended rotary handle the door must be opened to access the

rating plate

Reference Basics of Circuit Breakers For Electrical Engineers (additional info for practical usage)- Rockwell

Recommended EE stuff

About Author

Edvard Csanyi

Edvard - Electrical engineer programmer and founder of EEP Highly specialized for design

of LV high power busbar trunking (lt6300A) in power substations buildings and industry

fascilities Designing of LVMV switchgearsProfessional in AutoCAD programming and web-

designPresent on Google+






copy 2015 EEP - Electrical Engineering Portal All Rights Reserved | Privacy Policy | Terms of Service | 31 queries in 0103 seconds Powered by CsanyiGroup





The general procedure for the selection of correctly rated circuit breaker follows the following scheme of seven

major questions you should answer

1

2

3

45

6

7

1 What is the task of the branch circuit or feeder

Will it be used for the protection of connecting leads protection of installation group-protection or motor protection

Select the appropriate circuit breaker type with or without the thermal overload protection Decide which type of

protective characteristic (cable or motor protection)

2 Which rated current setting rangeDo the setting ranges of the thermal and the magnetic release cover the requirements of the particular application

(protection of transformer or generator)

What is the task of the branch circuit or feeder

Which rated current setting range

Breakingmaking capacities rated operational voltage

Any special requirementsWhich type of co-ordination

What is the mode of mounting

Cross-section of the connecting wirecable






































circuit breaker)













connecting

leads to the

motors are to

be selected on

the basis of

the current

setting of the



























Note


rating plate



About Author

Edvard Csanyi















































circuit breaker)













connecting

leads to the

motors are to

be selected on

the basis of

the current

setting of the



























Note


rating plate



About Author

Edvard Csanyi

















connecting

leads to the

motors are to

be selected on

the basis of

the current

setting of the



























Note


rating plate



About Author

Edvard Csanyi































Note


rating plate



About Author

Edvard Csanyi











7 guidelines to select correctly rated circuit breaker _ eep

Documents