3 6 công tắc tơ và rơ le nhiệt CB dùng cho động cơ

CB dùng cho động cơIEC 947-4-1 : Motor starters & contactors The main points of the standard: .More stringent testing on components - Insulation impulse voltage test - Increase in making

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3.6 Công tắc tơ và Rơ le nhiệt CB dùng cho động cơ

Công tắc tơ

Rơ le nhiệt

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CB dùng cho động cơ

Necessity for motor protection

Approximate percentages cause of motor faults:

 Correct design: a suitable motor has to be selected for each

application.

 Professional operation: professional installation and

regular maintenance are preconditions for fault-free operation.

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Necessity for motor protection

To guarantee fault-free operation of an electrical drive:

 Good motor protection:

• It must not be tripped before the motor is put at risk.

• If the motor is put at risk, the protection device has to operate before any damage occurs.

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• If damage cannot be prevented, the protection device has to operate quickly in order to restrict the extent of the damage as much as possible.

Variable speed

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IEC 947-4-1 : Motor starters & contactors

The main points of the standard:

.More stringent testing on components

- Insulation impulse voltage test

- Increase in making and breaking capacity requirements

(performance and electrical durability)

.Creation of new utilization categories

- Trip classes for overload relays (normal / long starting time)

- New utilization categories for contactors

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New utilization categories for contactors

(capacitor switching, transformer switching, )

. Coordination of protections

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Example on Telemecanique Contactors

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integral

Example: "D" contactor

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Example

Type "D2" additions

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• In conformity with IEC 947-4

Contactor

• Provides control of the motor with considerable

durability ( 1 to 2 millions operating cycles in AC-3

category)

• Provides cut-off of the power circuit when the

thermal overload relay trips

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!

Absolute limit: breaking capacity

The contactor must not be stressed over

its breaking capacity.

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Rated operational voltage (Ue)

For 3-phase circuits it is expressed as the voltage between phases

Definitions and comments (IEC 947-1)

For 3 phase circuits it is expressed as the voltage between phases

Rated operational current (Ie)depends on: rated operational voltage,

operating rate and duty, utilisation category and ambient temperature

around the device

Rated conventional thermal current (Ith) The current which a closed

contactor can sustain for a minimum of 8 hours without its temperature

rise exceeding the limits given in the standards

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Permissible short time rating The current which a closed contactor can

sustain for a short time after a period of no load, without dangerous

overheating

Rated operational power (expressed in kW) The rated power of the

standard motor which can be switched by the contactor, at the stated

operational voltage

Rated breaking capacity This is the current value which the contactor

can break in accordance with the breaking conditions specified in the

IEC standard

Rated making capacity This is the current value which the contactor

can make in accordance with the making conditions specified in the

IEC standard

Electrical durability yThis is the average number of on-load operating g p g

cycles which the main pole contacts can perform without maintenance

The electrical durability depends on the utilisation category, the rated

operational current and the rated operational voltage

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• Rated insulation voltage (Ui)

Rated insulation voltage (Ui)

• Rated impulse withstand voltage (Uimp)

• On-load factor (m) m = t/T

Cycle duration (T): duration of current flow (t) + time at zero current

• Pole impedance

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• Mechanical durability

• Rated control circuit voltage (Uc)

Utilization category (IEC 947-4)

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Application: utilization category (IEC 947-4) a.c applications

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Application: utilization category (IEC 947-4)

d.c applications

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Application: characteristics LC1-D and LP1-D Contactors

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Contactor selection guide for utilization category AC-3

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Contactor selection guide

according to required electrical durability

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Contactor selection guide

according to required electrical durability

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21

Thermal overload relays

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• Conforming to IEC 947-4 specifications

• Protects the motor, line and devices

current multiples

!

Protection curves (conforming to IEC 947-4)

Trip classes of a thermal relay

(conforming to IEC 947-4)

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Trip classes of a thermal relay (conforming to IEC 947-4)

The four trip classes of a thermal relay are 10 A, 10, 20 and 30 (maximum

tripping times at 7.2 In).

Classes 10 and 10 A are the most commonly used.

Classes 20 and 30 are reserved for motors with difficult starting conditions.

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Short-circuit protective devices

by fuses

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by circuit-breaker

Thermal-magnetic motor circuit-breaker

Magnetic circuit breaker (MA)

Contactor

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Contactor

Thermal relay

• Protection by circuit-breaker: • Protection by aM or gl fuses:

- conforming to IEC 947-2

- limited I 2 t

- limited electrodynamic stress (I peak)

- conforming to IEC 269-1 and 269-2

- limited I 2 t

- limited electrodynamic stress (I peak)

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the SC circuit-breaker must be protected against overloads

by a thermal overload relay

aM fuses must be protected against currents from In to

4 In by a thermal overload relay

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• 3 requirements for breaking of a short-circuit current:

Protection by circuit-breakers

3 requirements for breaking of a short circuit current:

- to detect the faulty current very early

- to separate the contacts very quickly

- to limit the short-circuit current

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Protection by circuit-breakers

Magnetic-thermal motor circuit-breakers

GV3-M GV2-P

35 to 100 kA with 415 V

25 to 80 A

50 to 100 kA with 415 V 0.1 to 25 A

25 to 220 A

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stock of spare cartridges

• Fuse cartridges with strikers:

used with a mechanism against

single phase operation, they

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single phase operation, they

enable the motor to be stopped

immediately if the cartridge melts

Fuse type

aM type fuses  Motor and transformer protection

Be designed to withstand high current peaks of a very short

duration They must be combined with a thermal overload

relay coupled with a contactor.

gl type fuses  lighting circuit, supply line and furnace

protection

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protection

They are more widely used but whose limiting capacity is

weaker than that of aM type fuses.

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Fuse protection

• Operation:

- the short-circuit current heats and melts the fuse element

- the silica smothers the electric arc by melting

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Fuse selection

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Disconnection

L.V Electrical Distribution

Switching Short circuit protection Overload protection

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Power Control

Motor

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What is the object of coordination?

• To provide protection for personnel and equipment whatever

levels of overcurrent are encountered (overload or short circuit) ( )

• To reduce maintenance costs in the event of failures by

minimizing the repair time and equipment replacement costs.

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• It prioritizes the protection of personnel :

Coordination of the protection devices

The spirit of the coordination standard IEC 947-4

It prioritizes the protection of personnel :

- no manifestation is accepted outside the enclosures

- no fire hazard

• It takes into account equipment maintenance : limits the risks of

damage at the start concerned

• Reduction of downtime : continuity of service for increased y

productivity

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What is a coordinated starter ?

protective device with a contactor and an overload relay.

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Energy I 2 t

Breaking/making capacity

Coordination and contactors

DANGER

TYPE 1

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TYPE 2

Ip current

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DANGER: No coordination

In case of a short circuit

High risks for operators and personnel

High risks for installations (fire, )

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All motor starter components will have to be replaced

before restarting

Coordination type 1 (IEC 947-4-1)

Coordination type 2 (IEC 947-4-1) Total coordination (IEC 947- 6-2)

The coordination level of a given motor starter

depends entirely on:

- the electrical environment

- the selection of the motor starter components

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(IEC 947-4-1)

No danger to persons or installation

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IEC 947-4-1

No dangerto persons or installation

No damageto the starter is allowed

The risk of contactor contact welding is acceptable, provided the

contacts can be separated easily

Settings of starter do not need to be readjusted

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Electrical insulation must be retained after the incident and the motor starter must

be able to operate following the short circuit

Before restarting, a simple checkis sufficient

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Total coordination (IEC 947-6-2)

No danger to persons or installation.

No damage to the starter, no contact tips welding is allowed,

electrical insulation must be maintained.

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Immediate restarting without inspection of starters

Example: Applications in building sector

starter Toxic fume extractor fanTotal High performance

coordination starter (integral)

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Example: Applications in industry

starter

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Petrochemical continuous Total High performance

Relay operating curve

Relay thermal stress limit (bimetal)

LC1-F

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motor ln I start I magn.

20- 30 ms

the class

Circuit-breaker

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Motor starter structures2-product solution: motor circuit-breaker + contactor

Tripping time

< 10 s

Circuit-breaker operating curve

Contactor breaking capacity limit

LC1-D GV2-P

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20- 30 ms

Micrologic 2.2M/2.3M – Motor protection

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Micrologic 2.2M/2.3M – Motor protection

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GV – Motor protection

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1 3 poles from cold state

2 2 poles from cold state

3 3 poles from hot state

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GV – Motor protection

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- protection against short-circuits

This type of device is defined in a special section of the IEC 947

standard: IEC 947-6-2 for control and protection devices

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relay operating curve

Operating curves

1-product solution

the magnetic operating curve can be set at 6 to 12 Ir max with 32 and 63 ratings

combined and integral

18 and 32 <10 s

integral 63 < 20 s

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20 to 30 ms

Coordination of the protection devices type 1 coordination (IEC 947-4-1) 380/415 V

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type 2 coordination (IEC 947-4-1) 380/415 V

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