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How to select MPCB?

Created by: PISCEAN 2010 at: 6/26/2013 8:49 AM (22 Replies)

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6/27/2013 10:23 AM	Rate (0)
PISCEAN 2010 Diamond Member Joined: 4/23/2010 Last visit: 5/7/2023 Posts: 8034 Rating: (855)	Ok. No problem

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6/27/2013 4:22 PM	Rate (0)
PISCEAN 2010 Diamond Member Joined: 4/23/2010 Last visit: 5/7/2023 Posts: 8034 Rating: (855)	Hello Experts, Just athought. 3VU MPCB technical catalogue says, MPCB triping charachterstic is inverse time & MPCB trips at 600% of rated current. Inrush current of motor is not more than 10 sec & inrush current of motor is max 2.5 times the rated current. Even then in our case why MPCB trips. Can any one help? Thanks in advance. DEEP.

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6/28/2013 6:20 AM	Rate (1)
Valli Posts: 262 Rating: (45)	Hi, We have faced similar issues and resolved it with the introduction Class 20 MPCBs. But in your case we dont have MPCB of 5A in class 20. Can we have a possibility tointroduce contactor and relays in the circuit for providing overload protection to the motor and let the MPCB to provide protection from short circuit current only.
Valli Posts: 262 Rating: (45)	Last edited by: Valli at: 6/28/2013 6:21 AM
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7/1/2013 8:41 PM	Rate (0)
Vithani Platinum Member Joined: 7/8/2009 Last visit: 8/9/2022 Posts: 1974 Rating: (475)	Valli Can we have a possibility tointroduce contactor and relays in the circuit for providing overload protection to the motor and let the MPCB to provide protection from short circuit current only. Contactor and relay for overload protection?? How? Anyways, I want to share something here We were having one problem of GMU breakage in one of the Application. We were having 4 GMU with similar rating and application and in 3-4 months we had breakdown in couple of them So we decided MPCB settings to be adjust at low level. Motor rated was 20A but we adjusted MPCB at 16A but still we had 2 more breakdowns Then we installed Drive for it(MM440) and trip setting done as discussed in PARAMETER SETTINGS TO TRIP MM440 ON OVERCURRENT for 16A 0.7sec and till then for 2 years we don't have any GMU breakage What I am trying to say is, MPCB didn't protected ourGMU because it takes time even if current goes to 16A. It will trip as per its thermal curve and if I want limit neck to neck, I must use very low rating MPCB and by doing so, it will trip on Starting or stopping current pick This issue is something similar which discussed here, although application is different. PISCEAN 2010, please make sure for how much time overload is allowed, because MPCB will take some time to trip depending upon how much current is going. For instant trip, you have to look for other options too Regards, Devesh Vithani
	Last edited by: Vithani at: 7/1/2013 8:41 PM I dont Like people driving Fast, thats the reason I overtake them ;)
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7/2/2013 6:27 AM	Rate (0)
PISCEAN 2010 Diamond Member Joined: 4/23/2010 Last visit: 5/7/2023 Posts: 8034 Rating: (855)	Hello Devesh, Nice to read your information. I am very much impressed by your each post, which has clear & indepth technical explanation. I gained a lot thru your post. Thanks. Now to your question. Yes I want MPCB to trip if the motor draws current 5A for 1 minute time duration. Thus we want to ensure or safeguard hydraulic pump from overloading. I know, pump failuer is not electrical problem. But to isolate the causes, hydraulic expert has suggested this protection. BTW what is meant by GMU? Regards, DEEP.

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7/2/2013 6:40 AM	Rate (0)
Valli Posts: 262 Rating: (45)	Vithani Valli Can we have a possibility tointroduce contactor and relays in the circuit for providing overload protection to the motor and let the MPCB to provide protection from short circuit current only. Contactor and relay for overload protection?? How?
Valli Posts: 262 Rating: (45)	Last edited by: Valli at: 7/2/2013 6:42 AM Dear Devesh, r u really surprised or u dont know that basic DOL is consist of only contactor and overload relay which gives overload protection. This problem of MPCB selection can only be attended by the introduction of an overload relay and contactor in the circuit. In this case overload relay will be kept at 5A or so, and right rating of MPCB shall be used to provide short circuit protection. Type II co-ordination chart is available for attending such cases Last edited by: Valli at: 7/2/2013 6:41 AM Last edited by: Valli at: 7/2/2013 6:41 AM
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7/2/2013 6:42 AM	Rate (0)
Vithani Platinum Member Joined: 7/8/2009 Last visit: 8/9/2022 Posts: 1974 Rating: (475)	Hello Deep Thanks for your nice word It always gives nice feel when someone is got something useful from my posts GMU means Gear Motor Unit where Gearbox is coupled with Motor itself - in my case also, Problem was not electrical but sudden jerk was causing failure in Gear so instant tripping was required For your case too, 5A for 1 min, make sure you are selecting that MPCB which will trip as per your timeline Regards, Devesh
	I dont Like people driving Fast, thats the reason I overtake them ;)
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7/2/2013 6:47 AM	Rate (0)
Vithani Platinum Member Joined: 7/8/2009 Last visit: 8/9/2022 Posts: 1974 Rating: (475)	Valli Dear Devesh, r u really surprised or u dont know that basic DOL is consist of only contactor and overload relay which gives overload protection. This problem of MPCB selection can only be attended by the introduction of an overload relay and contactor in the circuit. In this case overload relay will be kept at 5A or so, and right rating of MPCB shall be used to provide short circuit protection. Type II co-ordination chart is available for attending such cases Hello Mr Valli, I know enough basics about DOL and all.. You considered OLR as a replacement of MPCB and that surprised me Please go through complete thread, and try to understand what user is trying to ask Regards, Devesh
	Last edited by: Vithani at: 7/2/2013 6:48 AM I dont Like people driving Fast, thats the reason I overtake them ;)
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7/2/2013 7:04 AM	Rate (0)
PISCEAN 2010 Diamond Member Joined: 4/23/2010 Last visit: 5/7/2023 Posts: 8034 Rating: (855)	Vithani Hello Deep Thanks for your nice word It always gives nice feel when someone is got something useful from my posts GMU means Gear Motor Unit where Gearbox is coupled with Motor itself - in my case also, Problem was not electrical but sudden jerk was causing failure in Gear so instant tripping was required For your case too, 5A for 1 min, make sure you are selecting that MPCB which will trip as per your timeline Regards, Devesh Hello Devesh, Yes. Its absolutely true, you got the point. Just I am looking for the similar protection. Regards, DEEP.

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7/2/2013 8:40 AM	Rate (0)
PISCEAN 2010 Diamond Member Joined: 4/23/2010 Last visit: 5/7/2023 Posts: 8034 Rating: (855)	Hello, Does any one have idea about 3VU & 3RV MPCB s/c breaking capacity?

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