Types of MCCB

What is Google?

just not getting to the point answer on google...!!

Regs,

OFFS: http://en.wikipedia.org/wiki/Circuit_breaker

1. By adjustable trips of MCCB, are you referring to different trip class: like 10A, 10, 20, and 30?

2. What do you mean by: trips are always fixed in MCB? I am aware that B, C, D, K, Z and S curve exists in MCB.

Regs,

Thanks JRaef:

>>thermal trip on a 50A MCCB can be adjusted from 25 to 50A, and the magnetic trips from 100 to 500A.

- is this 25 to 50 A and 100 to 500 A range for 50 A MCCB applied to say 100 A MCCB(and all other MCCBs) by simple ratio ie. thermal trip 50 to 100A; and magnetic trip from 200 to 1000A ??

I have 17 kW motor, giving current of 24.5 A FLC.

1. Starting current for DoL starting would be: nearly 245 A. (10 times)

2. Starting current for Star Delta starting would be: 123 A. (5 times)

3. Inrush currents would be for star delta starting (as I have studied): 490 A. (20 times).

4. 24.5 A FLC would give a MCCB of 61.25 Amps (so 63A MCCB can be selected as per standard ratings), and conductors should be of 30.6 A.

is this okay?

Regs,

Hi,

1. What is the meaning of "frames" of MCCB. I came across it when studying MCCBs catalogue.

2. What is four pole with switched neutral MCCB ie. 4PwSN ?

Regs,

Why do 20 Questions (rhetorical question)?

Please put all the questions in the original post next time, as it enables a quicker response to arrive.

Switched neutral means that you've a 4th pole which is switched but not protected, it's explained in some other topic. Switched neutral is often optional but in some cases it's mandatory (depends on local regulations). Of course it's forbidden to switch a PEN.

Protected neutral means that the neutral is protected like a phase, though in some cases it can be rated below or above 100%. Protected neutral is interesting if there's a high amount of non-linear loads (harmonics can lead to neutral currents exceeding phase currents).

BTW There are also MCCB (Moulded Case Circuit Breakers) featuring a specialized motor protection release, they can be used without thermal relay and the good ones are also sensitive to phase unbalance (but one tripped you must switch on again manually unless you've an expensive magnetic or, for the larger sizes, motor drive; while thermal relays often have a manual/automatic reset selector).