90
Low Voltage Switch Gear
Appendix
Coordination type
Status of a switchgear combination (motor starter) during and after
testing at
rated conditional current
:
Coordination Type “1“:
- No risk to persons or installations
- No requirement for immediate readiness for renewed operation
- Damage to the starter is permissible
Coordination type “2“:
- No risk to persons or installations
- Starter is capable of renewed operation
- No damage to the starter with the exception of a slight welding of
the contacts, provided they can be separated without significant
deformation.
Positive opening operation
(IEC 947-1; 2.4.11/IEV 441-16-12)
This opening operation is designed to ensure that auxiliary contacts
of a switching device are always in the respective positions corre-
sponding to the open or closed position of the main contacts. The
contacts of a contactor are
interlocked opposing contacts
, pro-
vided they are mechanically linked in such a way as to ensure that
normally open and normally closed contacts can never be closed
simultaneously.
This arrangement must also ensure that minimum contact separation
of 0.5 mm is maintained over the entire lifespan of the device, even
during a fault, e.g. the welding of one contact.
The relevant German Trade Association requires the use of contac-
tors with interlocked opposing contacts for control systems on power
presses in the metal processing industry.
Positive/enforced
operation/actuation
This describes an arrangement where a link between the actuator
and the switching element ensures that the force exerted on the actu-
ator is transferred directly, i.e. without the intervention of sprung
parts, onto the switching element.
Positive opening
(IEC 947-1; 2.4.10/IEV 441-16-11)
An opening operation which ensures that the main contacts of a
mechanical switching device have attained the open position when
the actuator is in the Off-position.
Symbols used in Technical Data and Formulae
DF Duty
factor
I
cn
Rated short-circuit breaking capacity
I
cs
Rated service short-circuit breaking capacity
I
cu
Rated ultimate short-circuit breaking capacity
I
e
Rated operational current
I”
sc
Transformer initial short-circuit current AC
I
n
Rated current
I
NT
Rated transformer current
I
q
Rated conditional short-circuit current
I
r
Set value of overcurrent release
I
rm
Response value of non-delayed short-circuit release
I
th
Conventional free air thermal current
I
the
Conventional thermal current of enclosed devices
I
u
Rated uninterrupted current
S
NT
Transformer rating
U
c
Rated actuating voltage
U
e
Rated operational voltage
U
i
Rated insulation voltage
U
imp
Rated impulse withstand voltage
u
k
Transformer short-circuit voltage
U
s
Rated control voltage
