installation of fixed masterpact™ nw circuit breakers in ... · installation of fixed...

Data Bulletin 0613DB150104/2015

Installation of Fixed Masterpact™ NW Circuit Breakers in Electrical EquipmentClass 0613Retain for future use.

© 2015 Schneider Electric All Rights Reserved

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Introduction This document is focused on Masterpact™ NW circuit breaker mechanical installation guidelines. Other installation guidelines, such as electrical rules, are detailed in standards, catalogs, and regulatory requirements and must also be followed.

The following critical topics will be discussed:

• Masterpact NW circuit breakers• Equipment architecture• Circuit breaker installation in the equipment• Installation considerations on Masterpact NW circuit breaker operation• Circuit breaker installation in the equipment• Busbar mounting• Interlocking systems

Masterpact NW Circuit Breakers Masterpact NW circuit breakers are energy-based devices using a spring-loaded mechanism to provide the power for circuit breaker operation. Circuit breaker mechanical energy is calibrated on 100% of Masterpact NW circuit breakers in the manufacturing facilities.This necessary energy is used to maintain the proper functioning of the circuit breaker.

Proper installation is crucial to maintaining the positive energy balance necessary for optimum operation of the circuit breaker over its expected duty cycle. Circuit breaker mounting and power connectors must be configured so as to not exert excessive loading on the circuit breaker terminals. The circuit breaker terminal must not be considered part of the busbar support structure.

Potential negative contributors impacting fixed circuit breaker operation include:

• Busbar weight applied to the circuit breaker terminals• Circuit breaker mounting insufficiently supported (“hanging” on the

busbar)• Cable loads applied to the busbars

NOTE: All of the above influencing factors can be minimized by using the drawout version of the Masterpact NW circuit breaker.

Installation of Fixed Masterpact™ NW Circuit Breakers in Electrical Equipment 0613DB150104/2015

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NOTE: The drawout version should be considered when continuity of service is critical because:

• It provides mechanical isolation of the circuit breaker from external loads by having a flexible connection at the plug-on connector.

• It allows simpler access for maintenance when necessary.

Equipment Architecture Equipment architecture must be designed to have a reliable mechanical mounting of the different components, especially:

• devices such as circuit breakers• busbars• cables

A robust equipment structure is a key element as it is the common mechanical reference for all equipment components.

The main functional sub-assemblies of the equipment (circuit breakers, busbars, cables) must be securely and independently fastened to the equipment structure (see Figure 2).

Figure 1: Drawout Masterpact NW Circuit Breaker

Figure 2: Equipment Architecture

Note:

Circuit breaker, bus structure, and cables must be fully and independently supported by the equipment structure.

Equipment Structure

0613DB1501 Installation of Fixed Masterpact™ NW Circuit Breakers in Electrical Equipment04/2015

3© 2015 Schneider Electric All Rights Reserved

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Installation of Circuit Breakers in Equipment

Masterpact NW circuit breakers can be installed in two different ways:

• Installation mode 1: mounted horizontally on rails

• Installation mode 2: mounted vertically on mounting brackets

In critical applications, especially when the circuit breaker is transported inside the cubicle, installation mode 1 is recommended. This mode, when using sufficiently stiff supports, makes the circuit breaker more stable in the equipment (the circuit breaker center of gravity is in the middle of the supports). The supports must be of sufficient stiffness to minimize support deflection

It is important to distribute the weight of the device uniformly over a rigid mounting surface such as rails or a base plate.

The mounting plane should be reasonably flat (tolerance on support flatness: 2 mm). This eliminates risk of deformation which could interfere with proper operation of the circuit breaker.

Figure 3: Installation Modes

Rail Mounting - Mode 1 Vertical Mounting - Mode 2

Good Practice

It is recommended to check:

• Circuit breaker is vertical in the equipment.• No visible movement of the circuit breaker when

applying vertical loads to the equipment such as shipping or seismic testing.


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Busbar Design Busbar installation guidelines have been created in order to minimize mechanical loading on and maximize isolation of the circuit breaker, especially when using fixed version.

Busbar electrodynamic withstand is a separate topic which is not addressed in this document.

Busbar / cables supports Listed are the main constraints to be taken into consideration when designing Masterpact busbar system. These are especially relevant when using fixed circuit breakers.

Busbar supports must be designed in order to bear:

• the weight of the bus bars (permanent load + dynamic loads during transportation)

• the weight of cables that are attached to the busbars• the cable loads (cable deflection during installation and operation)• the loads applied to the busbars during bolt tightening

Figure 4: Example of Recommended Busbar Support Design



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Mounting with Busbars and Cables

Cable Connections If cables are used for the power connections, make sure that they do not apply excessive mechanical forces to the circuit breaker terminals. For this, make the connections as follows:

• Extend the circuit breaker terminals using short bars designed and installed according to the recommendations for bar-type power connections:

— For a single cable, use solution A, below.— For multiple cables, use solution B, below.

• In all cases, follow the general rules for connections for busbars:

— Position the cable lugs before inserting the bolts.— The cables should be firmly secured to the framework E, below.

Figure 5: Examples of Mounting with Cable Connections

Solution A Solution B

A B

E E


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Busbar Connections The busbars should be suitably adjusted to ensure that the connection points are positioned on the terminals before the bolts are inserted see B, below. Ideally, the busbars contact the circuit breaker terminals with a light slip fit creating neither interference nor gaps.

The connections are held by the support which is firmly fixed to the framework of the equipment, such that the circuit breaker terminals do have to support the weight C, below (this support should be placed close to the terminals). Caution must be used to ensure that securing the support does not create additional loading on the circuit breaker terminals. (See page 8 for assembly sequence.)

Busbar Support Design Busbar supports have a double function:

• they bear the weight of the busbars systems; and• they act as interphase insulating spacers (see Figure 7).

It is highly recommended to separate the spacer and support functions into:

• an insulating part (thermoset material) as an interphase and electrodynamic withstand spacer; and

• a stiff non-magnetic metallic beam underneath to support busbar weight.

Figure 6: Examples of Mounting with Busbar Connections

Figure 7: View of Busbar Support in Schneider Electric Equipment

Thermoset Spacers Metal Beam



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Minimum Distance Between Circuit Breaker and First Support

The first busbar support or space shall be situated within a maximum distance from the connection point of the circuit breaker (see the table below). This distance must be respected so that the connection can withstand the electrodynamic forces between phases in the event of a short circuit.

Interphase Insulating Spacers Spacers are required between the busbars. Their main function is to ensure insulation between phases and support short circuit electrodynamic forces.

In order to avoid having any side stresses applied by the spacers to the circuit breaker, it is mandatory to have the exact same spacer pitch as circuit breaker pole pitch (+/- 0.2 mm max).

Functional clearance must be applied between the busbar thickness and the spacer grooves. Given that the designs are often statically indeterminate, it is important to evaluate the circuit breaker to busbar connection and ensure that interphase spacers do not interfere with it. This can be done via the use of clearances in the interphase barriers, the use of a tightening sequence, or both.

Good Practice

When using the fixed version of the Masterpact NW circuit breaker, it is recommended to use the minimum distance of 150 mm for all short circuit currents.

Table 1: Maximum Distance A Between Busbar to Circuit Breaker Connection and First Busbar Support

Prospective Short Circuit Current 30 kA 50 kA 65 kA 80 kA 100 kA 150 kA

Maximum Distance Between Busbar to Circuit Breaker Connection and First Busbar Support

350 mm 300 mm 250 mm 150 mm 150 mm 150 mm

Figure 8: Insulating Spacer Between Phases

Figure 9: Avoid Side Loading on the Crossbars

Avoid side loading on the busbars.


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Busbar Mounting Clearances When bolting busbars together, it is mandatory to allow a proper positioning of the busbars by maintaining the right functional clearances.

For example, busbar holes must be drilled or punched with a diameter 2 mm larger than the screw diameter. Use slotted holes when necessary.

Mounting / Tightening Sequence As mentioned previously, busbars and circuit breakers must not apply any loads on each other. Confirming this is of special importance an all installations using the fixed version of Masterpact NW circuit breakers.

Busbars and circuit breakers must be securely and independently fastened to the equipment structure.

The following mounting sequence is recommended:

1. Place the circuit breaker in the equipment (without tightening the brackets).

1. Close the circuit breaker.2. Mount and fasten power busbars to the structure without bolting busbars

and circuit breaker together (locating pins can be used if necessary).Check alignment between circuit breaker terminals and connecting busbars.

3. Tighten the bolts on circuit breaker terminals.4. At the end, tighten circuit breaker brackets.

Following this sequence will avoid loading of the circuit breaker terminals during mounting and tightening operations.

Bolt Tightening When tightening bolts, especially circuit breaker terminal bolts:

• Always use a torque wrench• Always use two hands / wrenches in order to minimize loads on

busbar supports / circuit breaker terminals during tightening

Figure 10: Mounting Sequence

OEM Installation Sequence Note:

Alternative viable installation sequences are possible, please consult your Schneider Electric technical support contact for assistance if you have any questions.

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Interlocking System On source changeover applications when a mechanical interlocking system is required, two different possibilities are offered:

• interlock with cables• interlock with rods

In critical applications, it is recommended to use vertical mounting and a rod interlocking system.

When not possible, cables can be used but installation rules as detailed in the Source Changeover Interlocking Instruction Bulletin must be strictly respected.

Figure 11: Interlock Systems

Table 2: Advantages and Disadvantage of Cables and Rods

Cable Rods

Vertical Architecture

Preferred Preferred

Horizontal / Other Architecture

Preferred —

Setup Difficulty — PreferredEffect on Circuit Breaker Closing Energy — Preferred

Interlock with Cables Interlock with Rods

Installation of Fixed Masterpact™ NW Circuit Breakers in Electrical Equipment 0613DB1501Instruction Bulletin 04/2015

Electrical equipment should be installed, operated, serviced, and maintained only by qualified personnel. No responsibility is assumed by Schneider Electric for any consequences arising out of the use of this material.

Schneider Electric, Square D, and Masterpact are trademarks owned by Schneider Electric Industries SAS or its affiliated companies. All other trademarks are the property of their respective owners.

Schneider Electric USA, Inc.800 Federal StreetAndover, MA 01810 USA888-778-2733www.schneider-electric.us

10 © 2015 Schneider Electric All Rights Reserved

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Disclaimer

Information contained within this Data Bulletin is for general purpose guidance only and it is intended for use by competent electrical industry engineers. It contains only brief summaries of aspects of the subject matter and does not provide comprehensive statements of the relevant switchgear industry practice. All information relates to circumstances prevailing at the date of publication and thus does not reflect extensively upon designs manufactured prior to this publication.

This guide is intended to provide guidance on design and manufacturing best practice for Fixed Breaker integration in Switchgear. It does not mean that any other design would not be suitable but this document is intended to guide integrators to get the highest performance from Schneider Electric Breakers.

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