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28October2022/Version 7
LEM reserves the right to carry out modifications on its transducers,
in order to improve them.
LEM International SA
Route du Nant-d’Avril, 152
1217 Meyrin
www.lem.com
ITZ 5000-S FLEX ULTRASTAB
Sweep function during overload status
The overload occurs when the primary current
I
P
exceeds a trip level such that the fluxgate detector becomes completely saturated
and, consequently, the transducer will switch from normal operation to overload mode.
This trip level is guaranteed to be greater than 110 % of
I
P N
DC
and its actual value depends on operating conditions such as
temperature and measuring resistance.
When this happens, the ITZ rack electronics will automatically begin to sweep in order to lock on to the primary current again and
the measuring can resume when the primary current returns in the nominal range between −
I
P N
DC
and +
I
P N
DC
.
In sweep mode, the secondary current will be a slope between −2 A and +2 A.
Thermal protection
The ITZ 5000-S has thermal shutdown circuitry that protects the electronics from damage.
The thermal protection circuitry disables the measuring circuit when the rack electronics temperature reaches approximately
65 °C and allows the transducer to cool. When this occurs, the status LED is switched off.
When the rack electronics temperature cools to approximately 60 °C, the measuring circuit is automatically re-enabled and the
status LED is again lit.
Over current protection - Electrical specifications
The over current occurs when the primary current exceeds 120 % of
I
P N
DC
.
To detect the over current with primary AC, the secondary current is full-wave rectified and is time-averaged by a low-pass filter.
Depending on the frequency range of the primary current, two cases appear:
- Low frequency range: DC – 1.6 Hz (over current slow)
In this case, the over current trip level is set to 120 % of
I
P N
DC
.
The secondary current is tracked until the primary AC peak exceeds this trip level. Then, the rack electronics shut down the
measuring circuit and wait until the primary AC peak becomes lower than the set trip level.
- High frequency range: 1.6 Hz – 1.6 KHz (over current fast)
In this case, the over current trip level is set to 160 % of
I
P N
DC
.
The secondary current is tracked until the primary AC peak exceeds this trip level. Then, the rack electronics shut down the
measuring circuit and wait until the primary AC peak becomes lower than the set trip level.
The frequency response characteristics of the over current trip level with a sine-wave primary AC is illustrated by the following
curve:
0
50
100
150
200
250
300
350
400
450
0.0
0.1
1.0
10.0
100.0
1000.0
10000.0
Frequency (Hz)
(DC)
Ty
pi
ca
l o
ve
rc
ur
re
nt
tr
ip l
ev
el
(% o
f
I
PN
DC
)
Typical over current trip level vs frequency
T
A
= 25 °C
