Motor protection - Schneider Electric

Compléments techniques
Complementary technical
information
Principe protection moteur
Principles for motor
L
NTIA
E
D
I
F
protection
CON
nly
se o
nal u
inter
La commande et la protection d’un moteur peut être réalisée à l’aide de un,
deux ou trois appareils combinés pour fournir les fonctions suivantes :
Commande
Sectionnement
Protection contre les courts circuits
Protection spécifique moteur (au moins protection thermique).
Quand ces fonctions sont réalisées par plusieurs appareils, ceux-ci doivent
être coordonnés de telle façon que pour n’importe quel type de défaut
électrique, chacun de ces appareils ne subira soit aucun dommage, soit un
dommage limité à un niveau accepté.
Une bonne coordination est essentielle pour la continuité de service.
Quand la commande et la protection incluent plusieurs appareils, le choix
du type de coordination dépend du niveau de continuité de service et de
sécurité requis. Ces conditions sont spécifiées par la norme CEI 947-4-1.
disjoncteur magnéto-thermique moteur
+ contacteur
c
c
c
c
disjoncteur magnétique moteur
+ relais thermique
+ contacteur
c protection court-circuit
c sectionnement
commande
protection surcharge
protection court-circuit
sectionnement
contacteur
c commande
relais thermique
c protection surcharge
contacteur
c commande
M
M
A motor may be controlled and protected using one, two or three devices
combined to fulfil the following functions:
Control
Disconnection
Short-circuit protection
Specific protection for motors (thermal protection, at least)
When these functions are implemented by several devices, they must be
coordinated so that whatever the type of electrical fault, devices will either
suffer no damage at all or damage restricted to an acceptable level.
Good coordination is essential for service continuity.
When the control and protection functions include several devices, the
choice of coordination type depends on the required level of continuity of
service and safety. The conditions are specified by Standard IEC 947-4-1.
thermal-magnetic motor circuit breaker
+ contactor
c
c
c
c
magnetic motor circuit breaker
+ thermal relay
+ contactor
control
overload protection
short-circuit protection
disconnection
c short-circuit protection
c disconnection
contactor
c control
thermal relay
c overload protection
contactor
c control
M
Blokset • chapitre 6
M
page 16
Compléments techniques
Complementary technical
information
Principles for motor
protection
IAL
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ly
D
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I
F nal use
CON
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Two types of coordination
Standard IEC 947-1 defines tests at different current levels. The purpose of
these tests is to subject the switchgear and controlgear to extreme
conditions.
Depending on the state of the components following the tests, the standard
defines two types of coordination.
Type 1: deterioration of the contactor and the relay is acceptable under
two conditions:
no danger to operating personnel
no damage to any components other than the contactor and the relay
Type 2: only minor welding of the contactor or starter contacts is
permissible and the contacts must be easily separated.
Following type-2 coordination tests, the switchgear and controlgear
functions must be fully operational.
Which type of coordination is needed?
Selection of a type of coordination depends on the operating conditions
encountered.
The goal is to achieve the best balance between the user's needs and the
cost of the installation.
Type 1:
qualified maintenance service
low cost, compact devices
continuity of service is not imperative or may be ensured by simply
replacing the faulty motor starter.
Type 2:
continuity of service is imperative.
Coordination of insulation
Standard IEC 947-1 defines in detail the points that must be taken into
account to achieve effective coordination (type 2).
Full compatibility between
the thermal relay and the magnetic release on the circuit breaker
upper limit of thermal relay and limit of circuit breaker thermal withstand
capacity
The breaking capacity of the contactor must be greater than the value of
the setting of the circuit breaker magnetic release.
If this is not the case, the contactor must be capable of occasionally
breaking a fault current for which the impedance is greater than or equal to
the value of the setting of the circuit breaker magnetic protection system.
Good withstand of each component to breaking stresses (neither the
contactor nor the thermal relay should be damaged in the event of a shortcircuit).
The circuit breaker itself must have adequate breaking capacity. Breaking
capacity must be greater than or equal to the maximum possible value of
the short-circuit at this level of the installation.
relay thermal stress limit
cable thermal stress limit
thermal relay operating curve
1.05 to 1.20 In
t
tD
1 to
10 s
20 to
30 ms
IM
ID
I'' I magn.
Iq
For better quality and greater safety, Schneider strongly recommends
the use of electromechanical starters, fitted with components that
have been selected and tested to meet Type 2 coordination
requirements.
Iq breaking capacity
of circuit breaker (type 1)
of combination (type 2)
MA type circuit breaker operating curve
Blokset • chapitre 6
page 18