Current carrying capacity of Cu busbar

Size in mm	Area sqmm	Weight/ km	current carrying capacity in amp ( copper ) at 35 deg.C
			AC ( no. of bus)				DC ( no. of bus)
			I	II	III	II II	I	II	III	II II
12X2	24	0.209	110	200			115	205
15X2	30	0.262	140	200			145	245
15X3	75	0.396	170	300			175	305
20X2	40	0.351	185	315			190	325
20X3	60	0.529	220	380			225	390
20X5	100	0.882	295	500			300	510
25X3	75	0.663	270	460			275	470
25X5	125	1.11	350	600			355	610
30X3	90	0.796	315	540			320	560
30X5	150	1.33	400	700			410	720
40X3	120	1.06	420	710			430	740
40X5	200	1.77	520	900			530	930
40X10	400	3.55	760	1350	1850	2500	770	1400	2000
50X5	250	2.22	630	1100	1650	2100	650	1150	1750
50X10	500	4.44	920	1600	2250	3000	960	1700	2500
60X5	300	2.66	760	1250	1760	2400	780	1300	1900	2500
60X10	600	5.33	1060	1900	2600	3500	1100	2000	2800	3600
80X5	400	3.55	970	1700	2300	3000	1000	1800	2500	3200
80X10	800	7.11	1380	2300	3100	4200	1450	2600	3700	4800
100X5	500	4.44	1200	2050	2850	3500	1250	2250	3150	4050
100X10	1000	8.89	1700	2800	3650	5000	1800	3200	4500	5800
120X10	1200	10.7	2000	3100	4100	5700	2150	3700	5200	6700
160X10	1600	14.2	2500	3900	5300	7300	2800	4800	6900	9000
200X10	2000	17.8	3000	4750	6350	8800	3400	6000	8500	10000

 

Siemens Power Engineering Guide (Protection, Substation Automation, Power Quality and Measurement)

DOWNLOAD :

 

http://www.energy.siemens.com/hq/pool/hq/energy-topics/power%20engineering%20guide/PEG_70_KAP_06.pdf

 

 

Current carrying capacities in amperes

Project Planing Manual : Enclosure Heat Dissipation

Download :

 

http://www.cmafh.com/images/Master%20PDFs/Rittal/Rittal%20Enclosure%20Heat%20Dissipation%20Manual.pdf

 

Selection of an instantaneous, or short-time-delay, tripping threshold

Tripping unit Applications

Low setting 
type B

§  Sources producing low short-circuit- current levels (standby generators)

§  Long lengths of line or cable

Standard setting 
type C

§  Protection of circuits: general case

High setting 
type D or K

§  Protection of circuits having high initial transient current levels (e.g. motors, transformers, resistive loads)

12 In 
type MA

§  Protection of motors in association with discontactors (contactors with overload protection)

 

Copyrights :

http://www.electrical-installation.org/enwiki/Selection_of_a_circuit-breaker

 

Choice of a circuit-breaker

Choice of a circuit-breaker

 

The choice of a CB is made in terms of:

 

·         Electrical characteristics of the installation for which the CB is intended

·         Its eventual environment: ambient temperature, in a kiosk or switchboard enclosure, climatic conditions, etc.

·         Short-circuit current breaking and making requirements

·         Operational specifications: discriminative tripping, requirements (or not) for remote control and indication and related auxiliary contacts, auxiliary tripping coils, connection

·         Installation regulations; in particular: protection of persons

 

 

 

Low Voltage Circuit Breakers

Based on IEC 60947-2 (LV switchgear and controlgear - Part 2: Circuit breakers):

 

In (Rated current)

 

The rated continuous / uninterrupted current that the circuit breaker can carry.

 

Icm (Rated short-circuit making current)

 

The short-circuit current that the circuit breaker can withstand as it is closing where the act of closing initiates the fault.

 

Icu (Rated ultimate short-circuit current)

 

The maximum symmetrical short-circuit current the circuit breaker can interrupt.

 

Ics (Rated service short-circuit current)

 

The breaking capacity such that the circuit breaker is tested to carry its current continuously. The test sequence verifies that the breaker can be returned to service. Ics is the maximum current the breaker can interrupt multiple times and be returned to service without being damaged and is expressed as a % of Icu.

 

Icw (Rated short time withstand current)

 

This is the steady state symmetrical fault current the breaker has to be able to carry for a duration of 0.05s to 3s without exceeding its thermal integrity.