ul508a: control panel short circuit solutions · short-circuit current rating of the industrial...

UL508A: Control Panel Short Circuit SolutionsSon DinhControl Panel Application SpecialistSchneider Electric

OEM Initi@tive 2008

Schneider Electric 2- Division - Name – Date

Agenda

1. Short Circuit Current Rating (SCCR) requirements

2.

UL508A, Supplement SB

3.

Impact On Panel Design

4.

Schneider Electric’s Solutions


Short Circuit Rating Requirements: Background

Purpose of National Electric Code (NEC) Article 409 – Industrial Control Panels

●Previously no specific requirements for the inspection of control panels

●Provides minimum requirements for panel construction

●Requirements enhances worker and application safety that previously did not exist

●Allows for a safer integrated installation by requiring panels to be marked with a Short Circuit Current Rating (SCCR)

●Requires all panels be marked with a SCCR rating


Short Circuit Rating Requirements: Marking

●

409.110 Marking. An industrial control panel shall be marked with the following information that is plainly visible after installation:1.

Manufacturers name, trademark or other descriptive marking by which the organization responsible for the product can be identified

2.

Supply voltage, phase, frequency, and full-load current3.

Short-circuit current rating of the industrial control panel based on one of the following:

a. short circuit current rating of a listed and labeled assemblyb. short circuit current rating established utilizing an approved method

FPN: UL508A-2001 Supplement SB is an example of an approved methodException to (3): Short-circuit current ratings are not required for industrial control panels containing only control circuit components.


Short Circuit Rating Requirements: Safety standards requirements

● Safety Standards Also Require Panels to Have a SCCR rating

UL508AStandard for Industrial

Control Panels

UL1995Standard for Air Conditioning and

Refrigeration Equipment

NFPA 79Electrical Standard for Industrial Machinery


Short Circuit Rating Requirements: What is appropriate SCCR for a panel?

Contributing Factors to Panel SCCR Rating:

● Installation Site ●

Short circuit fault current available to panel or equipment.

●

Power transformer and conductor impedances before supply terminals of control panel/equipment all impact and help lower available fault current.

●Panel Specifications ●

Facilities Engineer,

●

Consulting & Design Engineer,●

Panel/Machine Builder


Short Circuit Rating Requirements: Available fault current and appropriate SCCR rating


Short Circuit Rating Requirements: Available SCC at transformer output terminals

(Takes a very large transformer toallow for 65kA or higher fault current)


Short Circuit Rating Requirements: How is panel SCCR determined

●Test each panel construction and have described in follow-up procedure●

Costly and destructive testing required

●

Third party testing and certification required●Purchase previously tested combinations and

constructions●Use an approved method

●

like Supplement SB of UL508A (weakest-link).●

Compliance with UL508A = compliance with NEC 409.

Using interrupt rating of the main overcurrent protective device for the panel is not an accepted method


Agenda

1.

Short Circuit Current Rating (SCCR) requirements

2. UL508A, Supplement SB

3.


4.



UL508A, Supplement SB Calculation method based on power component rating

●SCCR Rating Based on Weakest-Link●

Lowest SCCR Rated Power Component in Panel

●

Only applicable to power circuit, control circuit not included in calculation

●Component SCCR rating determined by one of the following ●

Marked rating on component or on instructions provided with the component

●

Assumed short circuit rating from Table SB4.1●

Rating of a UL tested combination or UL508A Combination Motor Controller


UL508A, Supplement SB SCCR component marking

Exceptions: Power transformers, reactors, current transformers, dry-type capacitors, resistors, varistors, and voltmeters are not required to have a short circuit current rating.

Product Label:

Product Carton:


UL508A, Supplement SB Default SCCR values

●Table SB4.1 –

Unmarked Components Default SCCR Values

●

Requires branch circuit protection (Fuse or Circuit Breaker) upstream and sized per NEC, if applicable. This is not the stand alone SCCR rating for device.


UL508A, Supplement SB Tested Combination Motor Controller

ContactorSCCR = 10kA

Circuit BreakerSCCR = 65kA

Overload relaySCCR = 5kA

Untested Combination Motor Circuit SCCR = 5kA (weakest-link)

Tested Combination Motor Controller Circuit, SCCR = 65kA

UL508A Tested Combination Motor Controller = 65kA

SCCR rating of tested combination is

higher than SCCR rating of individual components that

make up the motor combination


DisconnectSwitch

SCPD

Controller

Overload

Motor

Load BreakSwitch

or

Type E Example

Type D Example

UL508A, Supplement SB What is a UL Combination Motor Controller?

Classification:

●Type A Fuse

●Type C Thermal-magnetic breaker

●Type D Instantaneous trip breaker

●Type E Self Protected

●Type F Self Protected –Manual Motor Controller


Agenda

1.


2.


3. Impact On Panel Design

4.



Impact on Panel Design: How UL508A impacts OEMs

●Component Selection Is Critical In Order To Achieve Desired SCCR

Rating ●

Specific SCCR rated components and tested combinations are a must

●

Extremely difficult to obtain a high SCCR rating by intermixing components from different manufacturers

●Panel Design Considerations●

One size fits all design will require Higher SCCR rated components and will increase costs for everyone involved,

●

High SCCR rated panels may require more enclosure volume,●

Component selection may be limited depending on desired SCCR rating,

●

Determining panel SCCR rating will require more labor and supporting documentation,

●

100kA rated panel may not be safer or protect equipment as well where only a 5 or 10kA fault current is available,


Impact on Panel Design: How UL508A impacts OEMs

● Installation & Maintenance Considerations●

Is panel rated for available fault current of installation site,

●

May be asked by inspector or customer to prove and provide calculation and supporting documentation in the determination of SCCR rating,

●

Field modifications and upgrades,●

Replacement parts will need to be like for like,


Agenda

1.


2.


3.


4. Schneider Electric’s Solutions


Schneider Electric solutions UL508A Knowledge

UL508A Web sitewww.oem.schneider-electric.com> Standards and legislation

●

Interactive NEC Code Adoption Map●

Extensive FAQs & literature

●

How to establish SCCR rating Flowcharts

●

Industry’s broadest offering of UL validated and tested combination motor controller data


Schneider Electric solutions UL Tested Solutions

Up to 100kA Combinations 42kA to 130kADrives** SCCR:Up to 100kA -

SqD breakers

Up to 65kA-

GV (Type E) motor circuit protectors,

Up to 100kA-

fuses

Up to 100kA Combinations

Circuit breakers 10 to 100kA

UL508A 65kA Soft-Start

Combination

Contactors**:

D.P. = 100kA w/fuses & 65kA w/ Square D Breakers

IEC –

100kA w/fuses

** Pending product label/documentation update


Schneider Electric solutions Tested combination motor controller data benefits

●Lower cost through fewer components

●Tested and UL validated and certified

●Meet all your application needs

●Less documentation required to prove SCCR rating

●Reduce labor costs & simplify panel construction and calculation of panel SCCR rating


Schneider Electric solutions UL validated data available online


Schneider Electric solutions UL508A Combination Motor Controller Data

1.

UL ID number is the documentation for the combination. Data is on Schneider Electric and UL’s UL508A website.

2.

Required components for each combination are specified.

3.

Combination SCCR rating (higher that any individual component forming the combination).

4.

Minimum required enclosure volume for combination specified.

5.

Schneider Electric UL File where construction is described and previously tested.


Conclusion

●Factors that determine panel SCCR rating?●

the available fault current to panel,

●

panel specifications (end-user, consulting or design engineer),

●Panel SCCR rating will impact●

component selection

●

panel design and cost

●Compliance Made Simple●

Schneider Electric offers a full range of power protection, automation, and control products with SCCR ratings ranging from 10kA to 100kA

●

Schneider’s extensive UL508A knowledge online

ul508a: control panel short circuit solutions · short-circuit current rating of the industrial...

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