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34
Functions
Functions
(3) Standard type electronic release SU20S
Circuit breakers with frame size from Ex9M2- Ex9M6 are all available with standard type electronic release SU20S for AC distribution protection,
with operating ambient temperature of -25°C~+70°C and rated operating current of 32A-1600A.
The standard type electronic release provides 4 stage protection (LSIG):
Long time delay overload protection L
This is an inverse time limit protection. The current setting I
r
is (0.4~1.0)I
n
, and the overload protection release time Tr is 3-18s, with increment of 1s.
Short time delay short circuit protection S
The short time delay short circuit current setting I
sd
is (1.5~10)Ir, with increment of 1A. The short time delay short circuit protection release time T
sd
is (0.1~0.4)s, with increment of 0.1s. This function can be used with downstream circuit breaker for selection protection. This function can also be
set to OFF.
Instantaneous short circuit protection I
The instantaneous short circuit current setting I
i
is (1.5~12)I
n
, with increment of 1A. This function can also be set to OFF.
Grounding protection G
The grounding current setting I
g
is (0.4~1.0)I
n
, with increment of 0.1 I
n
, the release time is (0.1~0.4)s, with increment of 0.1s. This function can also
be set to OFF.
Neutral pole protection
The neutral pole protection current I
rN
=(0.5,1)In, I
sdN
=(1.5~10)I
rN
, I
iN
=(1.5~12)I
rN
, the release time is the same as phase line protection.
Electronic release (SU20S)
Ex9M2
Ex9M3
Ex9M4
Ex9M5
Ex9M6
Overload protection
Current setting (A)I
r
=I
n
╳
0.4-1.0, increment 1A, no OFF
6I
r
Release timeT
r
(s)
3-18, increment 1s, precision ±10%
Short time delay short circuit protection
Current setting (A)I
sd
=I
r
╳
1.5-10, increment 1A, can be set to OFF, precision ±15%
Release timeT
sd
(s)
0.1-0.2-0.3-0.4
,
precision ±20% or ±40ms (which is bigger)
Instantaneous short circuit protection
Current setting (A)I
i
=I
n
╳
1.5~12
,
increment 1A, can be set to OFF, precision ±15%
Maximum release time (ms)
60
Grounding protection
Current setting (A)I
g
=I
n
╳
0.4-0.5-0.6-0.7-0.8-0.9-1.0
,
can be set to OFF, precision ±10%
Release time(s)
0.1-0.2-0.3-0.4
,
precision ±20% or ±40ms (which is bigger)
N pole protection
Current setting
I
rN
=(0.5,1)
╳
I
n
;
I
sdN
=(1.5~10)I
rN
;
I
iN
=(1.5~12)I
rN
Release time
Same as phase line protection
Motor fault types
Motor protection solution
Undervoltage
* The voltage of distribution system deviates from normal value, the voltage supplied to the
motor is much smaller than the rated voltage of the motor.
* The supplied voltage is too small which causes reduced motor output torque, when the output
torque is not big enough to drive the load, the motor will locked
* When the motor is locked, the rotor current will increase rapidly, which will cause overheat and
burn out the motor.
Overload
* The load driven by the motor is higher than the rated value which cause motor overload
* Mechanical fault, such as bearing wear, vibration, that causes increased mechanical loss and
decreased actual output torque to the motor, the result is the same as the one above
* Usually, motors can run with overload for a short period of time, however, long-term overload
can cause overheat and burn out the motor.
Short circuit
* Direct connection between positive and negative poles due to motor insulation aging or
breakdown.
* Man-made wiring mistake
* The most series short circuit fault is large instantaneous current that can burn out the motor
Phase unbalance or phase failure
Phase unbalance or phase failure can cause temperature rise and braking torque, which can
further accelerate the aging of the motor.
Noark provides the following two solutions for motor protection, please contact Noark before
ordering two-element solution.
Three-element solution
Circuit breaker with magnetic prot con thermal relay
Two-element solution
Circuit breaker with overload and short circuit prot contactor
Circuit breaker with
magnetic protection
(Isolation)
(Short circuit protection)
Contactor
(Connecting/disconnecting
power)
(Execute overload protection)
Independent thermal
relay
(Overload protection)
I
In
Id
Id
’
t
t
d
Motor direct start
current curve
I
e
= rated operating current of motor
I
p
= start instantaneous current peak
t
s
= motor start time
t
p
= start peak current time
m = typical motor start curve
c = example of motor protective release curve of circuit breaker with electronic release
。
I
r
t
unbal
t
sd
t
p
t
s
I
unbal
I
sd
I
i
Motor protection