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Old November 18th, 2013, 07:48 AM   #1
budiman
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Beginner in Panel Builder for PLC

Hi,

I'm trying to build a new panel for my first automation system.
i'm trying to use PLC Omron CJ Series with DI/O, AI/O, and also Thermocouple Input.
I'm still beginner for panel builder, and i'm quite confused on deciding some material for my panel.
I do have some simple questions that i need to know,
For example i have 3 motor in 3phase 380V 3,7kw 5HP, 5,5kw 7HP and 7,5kw 10HP, and the questions are
  1. What type of Breaker do i need to use? 3 pole MCB or NFB? And what is the different?
  2. How to determine the size of the Breaker?
Actually i still got many questions to ask if all of you would mind to help me.
Thx.


Best Regards,
Budiman Chandra
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Old November 27th, 2013, 05:25 PM   #2
Lancie1
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Quote:
What type of Breaker do i need to use? 3 pole MCB or NFB? And what is the different?
How to determine the size of the Breaker?
Do you mean a main breaker for the entire panel, or a breaker for each motor? For the main breaker you need one for the total amp load + 25% of largest motor. MCB (Main Circuit Breaker?) and NFB don't mean anything to me, outside of a specific brand or class. Maybe if you gave the brand, model, and catalog number, I could figure out what you are talking about.
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Old November 27th, 2013, 08:31 PM   #3
budiman
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Breaker for each motor,
No Fuse Breaker (NFB) or MCB you can see Mitsubishi brand,
And what is the different between MCB (Mitsubishi) with Motor Circuit Breaker from Schneider?
Thx.
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Old November 28th, 2013, 09:56 AM   #4
Lancie1
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For a motor, you need two types of protection: short-term, and longer-term. For the short time, you need a device that will allow a very large current to get the motor started, then in the longer term, you need a device that will trip at a much lower current. Breakers have been designed for motor starting and probably that is how the Motor Circuit Breaker from Schneider works. On the other hand, you can use a large general-purpose breaker that passes the short-term large current, but add a motor overload device for the long-term protection.

Every circuit breaker has its own characteristic Time-versus-Current trip curve, and every brand and model may have a slightly different trip curve.
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Old November 28th, 2013, 09:16 PM   #5
budiman
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So, compare between Schneider Motor Circuit Breaker GV2ME type Vs NF32 type from Mitsubishi, which one is better for protecting motor?

For mitsubishi brand, which one should i better use for protecting motor, NF32SW or MCB Domae 32A?

Thx
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Old November 29th, 2013, 09:45 AM   #6
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non fused breaker will usually have a lower SCCR rating in Ka than one with fuses, it is something you may also look into. IT depend from the power feeder to your panel to keep a low arc flash design but in manny places it is not a concern until someone get hurt.

But one brand vs another will get answer biased to everyone prefference. If you look for a breaker alone that would protect your equipement from short and also from overload, you will need to select it very closely looking at the amps curve vs time and this kind of device will be closer to a manual starter device that include short and motor overload protection than just a breaker.

I would use a main breaker and individual set of 3 time delay fuses for each motor before proper contactor and overload for each too and it will be standard and done!
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Last edited by Jeff23spl; November 29th, 2013 at 09:53 AM.
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Old November 29th, 2013, 01:44 PM   #7
Lancie1
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Quote:
For mitsubishi brand, which one should i better use for protecting motor, NF32SW or MCB Domae 32A?
The NF32SW appears to be a Motor Circuit Protector. It will provide the short-time trip for a motor. You will still need a motor overload relay rated for the size and voltage of your motor.

The MCB Domae 32A is a Miniature Circuit Breaker for general purposes, and it is not specific for motor starting and running. If you pick the right size, you could use it for a motor if you add an motor overload trip relay.
Quote:
So, comparing between Schneider Motor Circuit Breaker GV2ME type versus NF32 type from Mitsubishi, which one is better for protecting motor?
The Schneider GV2ME is an elaborate thermal-magnetic combination circuit breaker and motor controller, with a fixed magnetic trip at 13 times the rated breaker trip. The thermal unit is adjustable with a knob. This unit also has a Start button, Stop button, undervoltage trip, and optional shunt trip for remote motor control. It attempts to provide complete motor control in one unit, but is not directly comparable to the Mitsubishi breaker-only units.

Last edited by Lancie1; November 29th, 2013 at 02:00 PM.
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Old November 29th, 2013, 02:53 PM   #8
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if you don't want to use separate overload, you can use something like that for each motor as long as you have a main disconnect or main breaker

https://eb.automation.siemens.com/Da...tor_control%3E
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Old November 29th, 2013, 05:04 PM   #9
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The Mitsubishi circuit breakers (MCCB) provide adjustable trip current, branch circuit short circuit and
overcurrent protection, and CANNOT be used to provide motor overLOAD protection.

A MCCB (Mitsubishi/MOLDED CASE CIRCUIT BREAKER) is not the same as a MCP (GV/Motor Circuit Protector)
or MPCB (Motor Protection Circuit Breaker).

Molded case circuit breakers (MCCBs) provide branch and feeder short circuit, ground fault, and
circuit overcurrent protection, they do not provide motor overLOAD protection.

Motor Protection Circuit Breakers (MPCBs/MCPs) are application-specific variations of the MCCB, these breakers
combine the short circuit and isolation functionality of the MCCB with the motor overcurrent protection
of a traditional overload relay. These devices are traditionally used in two component starter applications,
with a contactor to control a motor load. Alternatively they can even be used individually as a manual starter,
although this application is not normally suggested for Molded Case versions of the MPCB due to their limited
mechanical life. MPCBs are UL 489 Listed as circuit breakers and are also UL 508 Listed as motor overload relays.

However, in North America, the Schneider GV motor circuit protectors CANNOT be used as circuit breakers, and would
require 1 circuit breaker (MCCB) upstream from the 3 GV motor protectors (to provide the 3 motor group branch short
circuit and overcurrent protection). The GV motor protectors DO provide adjustable motor overLOAD protection.
The controller and overload devices must be UL listed for group installation.

You would need one circuit breaker (Mitsubishi or other/or time delay fuses) feeding the 3 Schneider GV (or other type)
motor circuit protectors. The feeder CB rated at - (1.25 X FLA (LARGEST MOTOR) + FLA (M2) + FLA (M3)).

Feeder breaker (size) rating selection example;

This assumes that the circuit breaker selected has a voltage
rating equal or greater than the application and that the
interrupting rating is equal or greater to the available short
circuit current. The EXAMPLE panel contains a main feeder breaker
supply with three motor branch circuits.

In this example, the feeder is supplying a 3 phase 3-motor system
at a voltage of 480V.

Motor 1 is 10 Hp. Current value from Table 430.250
of the NEC is 14 A.
Motor 2 is 5 Hp. Current value from Table 430.250
of the NEC is 7.6 A.
Motor 3 is 5 Hp. Current value from Table 430.250
of the NEC is 7.6 A.

Current calculation is:
Motor 1 (14 A* 1.25) 17.5 A
Motor 2 7.6 A
Motor 3 7.6 A

Total 32.7 A

Since the total load comes to 32.7 A and there is not a
commercially available breaker available for 32.7 A, the NEC
allows the next largest standard-sized breaker to be used.
Therefore, a 35A MCCB (molded case circuit breaker) could
be selected to protect this control panel. This circuit breaker
provides branch circuit (feeder) short circuit and overcurrent
protection, but does not provide individual motor overload
protection. Note: each motor branch would also need protection,
and could be provided by a properly rated Schneider GV motor
circuit protector (MCP).
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