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Suggestion on How to Use - PowerPoint Presentation

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Suggestion on How to Use - PPT Presentation

Industry Trainers are encouraged to use this material in their sessions Download the presentation file Print the Notes pages and read them as you view the presentation in the Slide Show view In this way you see the slides in large format and have animation when available ID: 641906

fuses circuit class time circuit fuses time class current motor delay short trip rating ratings protection nec interrupting limiting

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Slide1

Suggestion on How to Use

Industry Trainers are encouraged to use this material in their sessions

Download the presentation file

Print the Notes pages and read them as you view the presentation in the “Slide Show” view. In this way you see the slides in large format and have animation (when available)Slide2

Types of Overcurrent Protective DevicesSlide3

Circuit Breakers

NEC

® Definition - Article 100

A device designed to open and close a circuit by

nonautomatic

means

and to open the circuit automatically on a predetermined overcurrent without

damage

to itself when properly applied within its rating.Slide4

Thermal-Mag CB Construction

Molded case

f

rame

provides insulated housing for components

Contacts

open and close circuit

Handle or Operating mechanism opens and closes contacts – cannot be “teased” - quick-make, quick break

Handle or

Operating

Mechanism

Contacts

Arc

Extinguishers

(Arc Chutes)

Molded

Case Frame

TerminalsSlide5

Trip Unit (not shown) detects overcurrent condition – triggers release of contacts

Contacts are pulled through

Arc Extinguishers (Arc Chutes)

which help to confine, divide and extinguish the arc when clearing an overcurrent

Terminals

typically rated 60/75 deg C

Thermal-Mag CB Construction

Handle or

Operating

Mechanism

Contacts

Arc

Extinguishers

(Arc Chutes)

Molded

Case Frame

TerminalsSlide6

Thermal-Magnetic CB Trip UnitSlide7

Trip Unit – Thermal

Overload - Bimetal element deflects and contacts trip bar which releases contacts.

Thermal-Mag CB Trip Unit - OperationSlide8

Trip Unit - Magnetic

Short Circuit - magnetic element’s electric field attracts trip bar armature and releases contacts.

Thermal-Mag CB Trip Unit - OperationSlide9

Molded Case Circuit Breaker (MCCB) Ratings

Voltage Rating:

NEC 240.83(E) & 240.85 cover circuit breaker voltage marking and basic requirements

AC assumed, Verify if rated for DC

Slash ratings (such as 120/240 or 480/277) can only be used on solidly grounded systems where the voltage to ground does not exceed the lower rating and the voltage between any

two conductors

does not exceed the higher

rating

Corner-grounded, resistance-grounded & ungrounded systems require “straight” rated

circuit breakers (240, 480 or 600)

2-pole CBs on corner-grounded systems require special ratings and must be marked “1 phase - 3 phase” Slide10

MCCB Ratings

Ampere Rating:

80% rated unless marked and applied in equipment for 100% rating - Typically rated up to 2500A

Interrupting Rating:

AC assumed unless marked, verify DC ratings with manufacturer

Interrupting rating varies, dependent upon voltage and manufacturer - Typical values - 10, 14, 18, 22, 25, 30, 35, 42, 50, 65, 100, 125, 200 kA.

MCCBs

applied on

corner-grounded, resistance (impedance) grounded, and ungrounded

systems may have lower

interrupting capabilities.Slide11

MCCB Types

Branch-Circuit

MCCBs:

Thermal-Magnetic and Electronic Trip

Current-Limiting and non-Current-Limiting

Listed and Recognized (mag-only MCPs for motor circuits) to UL 489Slide12

Thermal-Magnetic CB

Known as inverse time circuit breakers

Higher the current, faster it trips

Sustained overload may take may seconds to trip

Short-Circuit will cause the CB to open instantaneously and may take ½ to 1 cycles to clear the short-circuit

Instantaneous setting can be fixed or adjustableSlide13

Thermal-Magnetic CB – Instantaneous Trip

Fixed Instantaneous Setting

20A CB have fixed instantaneous setting of approximately 8 times the ampere rating.

Adjustable Instantaneous Setting

Typically 5-10 times the ampere rating.

Figure shows 100A CB

Setting of 5X = 500A = I.T.

Setting of 10X = 1000A = I.T.Slide14

Similar internal construction as thermal-magnetic circuit breaker.

Adjustable Trip Settings:

Long time pick-up (LTPU)

Long time delay (LTD)

Short-time pick-up (STPU)

Instantaneous

Override (may be fixed)

Short-time delay (STD)

Settings may include Ground Fault

Electronic Trip CBSlide15

Current Limiting CB

Similar to thermal-magnetic circuit breakers with

addition

of

current-limiting capabilities

Current limitation provided by blow-apart contacts, a fusible

limiter or

additional arc extinguishersIncreased interrupting ratings up to (200 kA) Current limiting circuit breakers limit the damage to downstream components for short circuits within their current limiting rangeSlide16

Motor Circuit Protector (MCP)

MCPs are mag-only circuit breakers.

MCPs

typically cannot be used to replace a thermal magnetic or electronic trip circuit breaker (unless in a motor circuit with a starter that is listed for use with the MCP) – NEC 430.52(C)(3).

A Mag-only (MCP)

trip

curve is

compared to a thermal-magnetic CB at the rightSlide17

Supplementary Protectors

Supplementary Protectors

Recognized to U.L. 1077 and limited per NEC 240.10.

Cannot

be used as a branch circuit protective device

(in

place of a UL 489 circuit

breaker). For supplemental protection of an appliance or other electrical equipment where branch circuit overcurrent protection is already provided, or is not required. Low interrupting ratings. Typically can be applied only on solidly grounded systems.

Most are short-circuit tested with fuses or a circuit breaker upstream and

must therefor be applied in series with an upstream fuse or circuit breaker.Slide18

Insulated Case (ICCB)

Larger physical size and amp ratings

Typically rated up to 5,000A with interrupting ratings

up to

100,000A or more

Electronic Trip

Units

Short-time delay optionsInstantaneous OverridesSlide19

Low Voltage Power Circuit Breaker (LVPCB)

Typically used in industrial facilities where selective coordination, circuit breaker maintenance, and drawout capability are required

.

Short-time delay option available without an instantaneous override, provides improved selective coordination capabilities.

Drawout capability means that these circuit breakers can be racked in and out of the

switchgear

for inspection and maintenance.

Utilize two-step stored energy operating mechanismOpening and closing springsOpening springs are charged when LVPCB is closed

Open-Close-Open operation without recharging

Close & Open is typically 5 cycles or lessAmp ratings up to 4,000A with interrupting ratings up to 200,000 amperesSlide20

LVPCBs

May be required upstream of MCCBs and ICCBs (which have instantaneous trips or overrides) for

selective coordination

capabilities

Can "hold-in" on faults for up to 30 cycles (.5 seconds) in order to achieve coordination with downstream devices

Typically equipped with adjustable electronic trip units with STD and without instantaneous override

Downstream components may need increased short-circuit current (withstand) ratingsSlide21

Fuse Basics

A “fusible” link or links encapsulated in a tube and connected to contact terminals.

Resistance of the link is so low that it simply acts as a conductor.

Can be single-element or dual-element construction

During an overcurrent the fusible link melts and opens the circuit to protect conductors and system

components from further damage. Slide22

Fuse Construction

Dual Element Time-Delay

Designed to be sized close to load and accommodate motor and transformer inrush which could not be accomplished by single-element non-time-delay or fast-acting fuses.

Overload (time delay) Element

Short Circuit (current limitation) ElementSlide23

Overload Operation

Dual Element Time-Delay

Under

a sustained

overload condition,

the spring

operated trigger assembly separates the “connector” from the short-circuit element, opening the circuit.Slide24

Short-Circuit Operation

Dual Element Time-Delay

Under a short-circuit condition, restricted portions of the short-circuit element melt and arc to burn back the resulting gaps until the arcs are suppressed by the arc quenching material and increased arc resistance.Slide25

Branch-Circuit Fuse Ratings

Branch-circuit fuse holders prevent installation of fuses that cannot provide a comparable level of protection.

When installed in rejection style clips, current-limiting branch circuit fuses cannot be replaced with fuses

that

are not current-limiting, have lower voltage ratings or higher current ratings than the

fuseholder

.

Branch-circuit characteristics include:10,000A Minimum Interrupting Rating up to 300,000A

125V AC Minimum Voltage Rating

NEC 240.60(C) covers required fuse voltage marking.NEC 240.60(A)(2) permits 300V cartridge fuses to be used on single-phase 277V lighting circuits.

NEC 240.61 allows fuses rated 600V or less to be used for voltages below their rating.Slide26

Branch-Circuit Fuse Classes

Fuse classes and UL/CSA/ANCE standard governing performance and characteristics include:

Class L – UL/CSA/ANCE 248-10

Class H – UL/CSA/ANCE 248-6,

& 7

Class K – UL/CSA/ANCE 248-9

Class RK1 & Class RK5 – UL/CSA/ANCE 248-12

Class J – UL/CSA/ANCE 248-8

Class T – UL/CSA/ANCE 248-15

Class G – UL/CSA/ANCE 248-5Class CC – UL/CSA/ANCE 248-4

Class CF - UL/CSA/ANCE 248-17Slide27

Class L

600V AC, 601A up to 6000A

Amperage case sizes include:

800, 1200, 1600, 2000, 2500, 3000, 4000, 5000, 6000

200kA Interrupting rating or higher

Time-delay or fast-acting

Time-delay typically 500% for 4 or 5 seconds

Current limitingRejection feature – class

and size rejecting

Applications:Main or large feeder circuitsMixed loads (time-delay)

Motor or transformer loads (time-delay)Slide28

Class H/K Fuses

250V AC or 600V AC, up to 600A

Amperage case sizes include:

30, 60, 100, 200, 400, 600

Interrupting rating is only 10 kA for Class H fuses, 50 kA to 200kA for Class K5 fuses.

Non-time delay or time-lag

These fuses are dimensionally the same as the Class R fuses, however, they do not have the rejection feature.

Renewable Fuses or One-Time Fuses

They are general purpose fuses for general applicationsSlide29

Class RK1, RK5

250V AC or 600V AC, up to 600A

Amperage case sizes include:

30, 60, 100, 200, 400, 600

200kA Interrupting rating or higher

Time-delay or fast-acting

Current limiting - RK1 more current-limiting than RK5

Rejection feature – prevents replacement of Class R fuses with Class H fuses - Notch in ferrule (for cartridge fuses) or blade

Applications:

Branch, feeder circuits Motors & transformers (time-delay)Slide30

Class J

600V AC, up to 600A

Amperage case sizes include:

30, 60, 100, 200, 400, 600

200kA Interrupting rating or higher

Time-delay or fast-acting

Current limiting

Rejection feature – class

and size rejecting

Space saving design compared to Class RApplications:Branch, feeder circuits

Motors & transformers (time-delay)Slide31

Class T

300V AC or 600V AC, up to 1200A

Amperage case sizes include:

30, 60, 100, 200, 400, 600, 800, 1200

200kA Interrupting rating

Fast-acting

Current limiting

Rejection feature – class

and size rejectingBest space saving design of any power fuseApplications:

Heating and lighting circuits277V single phase lighting circuits (300V fuses)Residential and multi-meteringSlide32

Class G Fuses

600V AC, up to 20A

480V AC, 25-60A

Amperage case sizes include:

15, 20, 30, 60

100kA Interrupting rating

Time-delay (6 to 60 amperes)

Current limitingRejecting feature

Length of fuse varies with the amperage

Applications: Small motors & transformers General applicationsSlide33

Class CC Fuses

600V AC, up to 30A

200kA Interrupting rating

Fast-acting or time-delay

Current-limiting

13/32” Diameter, 1-1/2” Length

Grooved ferrules provide rejection feature

Applications:

General purpose

Street lighting, lighting ballasts, heating, motor control circuits (fast-acting)Small motors or transformer circuits (time-delay)Slide34

Supplemental Fuses

Fuses can have many voltages and interrupting ratings within the same case size.

Interrupting ratings range from 35 to 100,000 A

Examples of supplemental fuses are ¼” X 1¼ ”, 5 X 20 mm, and 13/32” X 1½” fuses

Supplemental fuses can only be used where proper protection is already being provided by a branch circuit device or if protection is not required. Slide35

Cable Limiters

NEC 230.82(1) allows the application of cable limiters on the supply side of the service disconnect.

The application of cable limiters on the supply side of service-entrance conductors provides:

Short-circuit, current-limiting protection for downstream equipment

Decreased possibility of severe equipment damage or burn-down against high short-circuit currents.

Isolation of one or more faulted conductors.

Only the cable limiters in the faulted conductors open, other conductors remain in operation.

Helps keep

the service in operation and continuity of service is improved. Slide36

High Speed Fuses

Typically used for protection of drives, SCRs or sensitive electronic equipment

Very Current-limiting

NEC 430.52(C)(5) permits the use of high-speed fuses in power electronic devices in solid-state motor controller system if replacement fuses are marked adjacent to the fuses.

High-Speed Fuses

Required for protection

of VFD – Replacement

fuses must be marked

M

Replace with:

Bussmann

FWH-400A

VFDSlide37

GFCI Protective Devices

Ground-Fault Circuit Interrupter (GFCI)

Article 100 defines a ground-fault circuit interrupter as a device intended for the protection of personnel that functions to de-energize a circuit or portion thereof within an established period of time when a current to ground exceeds the values established for a Class A device.

Note: Class A ground-fault circuit interrupters trip when the current to ground has a value in the range of 4 to 6 mA or greater.Slide38

GF Protective Devices

Ground-Fault Protection of Equipment (GFP)

Article 100 defines ground-fault protection of equipment as a system intended to provide protection of equipment from damaging line-to-ground fault currents by operating to cause a disconnecting means to open all ungrounded conductors of the faulted circuit. This protection is provided at current levels less than those required to protect conductors from damage through the operation of a supply circuit overcurrent device.Slide39

Motor Circuit Devices

Manual Motor Protectors/Starters

Sometimes called MMPs

Provide motor overload protection per NEC 430.32(A)(1) & (B)(1)

Provide controller function (On-Off) per NEC 430.83(A)(1) (HP rated & Listed to UL 508)

Provide limited amount of short-circuit protection via a magnetic trip, but

not

acceptable for branch-circuit, short-circuit and ground fault protection (NEC 430.52). Slide40

Motor Circuit Devices

Manual Motor Protectors (Cont)

If marked “Suitable as Motor Disconnect” (and lockable in the “off” position per UL 508) – can be used as a motor disconnecting means if located between the final motor branch-circuit, short-circuit and ground fault protective device and the motor (NEC 430.109(A)(6).

Typically suitable for group motor protection applications (as long as they are protected by a branch-circuit device) per NEC 430.53(D).Slide41

Motor Circuit Devices

Self-Protected Starters

Often called “Coordinated protected starters” and “Type E” starters – Listed to UL 508 as a combination Starter.

Provide motor overload protection per NEC 430.32(A)(1) & (B)(1) and motor circuit (branch-circuit) protection per NEC 430.52(C)(6), by combining a magnetic short-circuit trip and adjustable motor overload in one package

.Slide42

Motor Circuit Devices

Self-Protected Starters

Provide controller function (On-Off) per NEC 430.83(A)(1) (HP rated & Listed to UL 508) and permitted as the motor disconnecting means per NEC 430.109(A)(5).

Many have slash voltage ratings and can only be applied on solidly grounded systems where the voltage to ground does not exceed the lower of the two ratings and the voltage between any two conductors does not exceed the higher of the two ratings.Slide43