MCCB

You could start by giving a lot more information. What type circuit? Cost difference?

thank you for your interest but i should say that during the meeting i have been aware this is part of mandatory term of contract and there were no choice.

regard

In my opinion, you cannot "inspire" someone to use something that is inappropriate for the application. There is a LOT that goes in to deciding on a Power breaker (i.e. ACB) vs a Distribution Breaker (MCCB). It's rarely a matter of opinion.

dear sir

thank you in advance for your respond yesterday i held meeting with my client i discuss him the advantage of ACB in complying IEC 60947 regarding to better capability of Ics and having better time discrimination in total final time coordination between incoming ACB abd outgoing MCCB but in our case we have 400A ACB 40KA@1Sec in out going feeder for protecting capacitor.

unfortunately he told me this is our mandatory rule of oil company and you shoul following it up.

Dear Mr. Alirahnama,

You Have mentioned that this breaker is used for protection of Capacitor feeder. Please give the correct load details. what is the kVAR of Capacitor?

I would wish to tell you that for Power factor correction capacitors, the switching design is a bit different due to the high inrush currents and the overvoltages it produces in the system due to switching and inherent characteristics of the capacitor. when i design the rating of switchgear, take a example: if 100 kVAR capacitor is required, i would multiply it by 2.6 times kVAR value(or sometimes 3 times) to get the current rating of switchgear. Depending on the frequency of switching of capacitors , the decision of ACB or MCCB should be done. As i have earlier said, the ACB is designed for better electrical and mechanical operations and higher Short-circuit current withstand value. and depending on the location and application, type of switchgear is decided. So you customer may be right in considering ACB. of course if you r looking from the cost point of view, you have to take the additional price from the customer.

Dear all,

If the client requires coordination between the 400A feeder and down stream MCCBs, he may requires ACB which can wait the down stream to trip first. MCCB-MCCB coordination is difficult or not possible.

Regards

This previous thread may also help: http://cr4.globalspec.com/thread/45169

I would suggest you first get the reasons why your client prefers ACB to MCCB. There may be technical or regulatory or commercial or cultural reasons. Then you can suggest (not inspire) with your reasons for using MCCB. One of the reasons your client prefer ACB for future maintenance facilities.

However, as an engineer, you should be faithful to the client and apply your diligent judgment to propose them whatever you feel well for the client – never propose something that has the interest only for your own side.

- MS

i think a mccb would be a good choice if u consider cost factor as it s cheaper than acb and as far as protection s considered it wont dissappoint ur client.....an Acb range starts from 800A in schneider ...so if u want to use it for a 400A then u ll have to use a additional micrologic and set it to trip when current exceeds 400A....this s very costly but highly reliable regarding maintenence and temperature withstanding capacity..........so if ur client is not bothered abt the budget then use acb or else use mccb.....i hope this gives u some hint......