LAX100-NP Datasheet, PDF (8/12 Pages) LEM – Current Transducer LAX SERIES

LAX series 16-100 A
Performance parameters definition
The schematic used to measure all electrical parameters is:
(C
1
=
C₂
=
100
nF,
R_M
=
50
Ω
unless
otherwise
noted):
+V_C
+
I_P
M ^IS
R_M ^C1
0V
C₂
This model is valid for primary ampere-turns Θ_P between
Θ -
Pmaxi
and
Θ +
Pmaxi
only.
At zero input current, the model for the offset is reduced to:
I
S
=
I
OE
+
I (T )
OT A
+
I_OM(Θ_Pmaxi)
In which I_OM(Θ_Pmaxi) is the magnetic offset current due to the
maximum input ampere-turns that have been applied to the
transducer.
-
-V_C
Figure 17 : standard characterization schematics
Ampere-turns and amperes
The LAX transducer is sensitive to the primary current linkage
Θ_P (also called ampere-turns).
Θ_P = N_PI_P (At)
With N_P the number of primary turn (1, 2 or 3
depending on the connection of the primary jumpers)
Warning : As most LAX user will use it with only one single
primary turn (N_P = 1), most of this datasheet is written with
primary currents instead of current linkages. The unit is kept as
ampere-turn (At) to make clear that ampere-turns are meant.
Transducer simplified model
The static model of the transducer at temperature T_A is:
I
S
=
G
Θ_P
+ error
ε ε In which error = I_OE + I_OT(T_A) + _GΘ_P + Θ Θ ( ) _{L Pmaxi Pmaxi}
With :
Θ_P
=
NI
PP
:
the
input
ampere-turns
(At)
Please read above warning.
Θ_Pmaxi
: the maxi input ampere-turns that have
been applied to the transducer (At)
I_S
: the secondary current (A)
T_A
: the ambient temperature (°C)
I_OE
I (T )
OT A
G
: the electrical offset current (A)
: the temperature variation of I at
temperature T (A)
O
A
: the sensitivity of the transducer (A/At)
ε_G
: the sensitivity error
ε_L (Θ_Pmaxi) : the linearity error for Θ_Pmaxi
Sensitivity and linearity
To measure sensitivity and linearity, the primary current (DC) is
cycled from 0 to I , then to -I and back to 0 (equally spaced I /
P
P
P
10 steps).
The sensitivity G is defined as the slope of the linear regression
line for a cycle between ± I .
The
linearity
error
ε_L is
PN
the
maximum
positive
or
negative
difference between the measured points and the linear regression
line, expressed in % of the maximum measured value.
Magnetic offset
The magnetic offset current I_OM is the consequence of a current
on the primary side ("memory effect" of the transducer's ferro-
magnetic parts). It is included in the linearity figure but can be
measured individually.
It is measured using the following primary current cycle.
I_OM depends on the current value I_P1.
IOM
=
Is(t₁) − Is(t₂ )
2
I_P (DC)
I_P1
0A
t
-I_P1
t₂
t₁
t
Ip(3)
Figure 18: current cycle used to measure magnetic and
electrical offset (transducer supplied)
070213/7
LEM reserves the right to carry out modifications on its transducers, in order to improve them, without prior notice.
Page 8/12
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