HO-NP-0000 Datasheet, PDF (15/16 Pages) LEM – Current Transducer

HO-NP-0000 SERIES
Performance parameters definition
Ampere-turns and amperes
The transducer is sensitive to the primary current linkage Θ_P (also
called ampere-turns).
Θ_P = N_P·I_P (At)
Where N_P is the number of primary turn (depending on
the connection of the primary jumpers)
Caution: As most applications will use the transducer with only
one single primary turn (N_P = 1), much of this datasheet is
written in terms of primary current instead of current linkages.
However, the ampere-turns (At) unit is used to emphasis that
current linkages are intended and applicable.
Transducer simplified model
The static model of the transducer at temperature T_A is:
V_out = G·Θ_P + overall error (mV)
In which error =
ε_G ·Θ_P·G + ε_L·Θ_P·G + TCG (T_A-25)·Θ_P·G + V_OE + TCV_OE·(T_A-25) (mV)
With:
Θ_P = N_P·I_P
Θ_{P max}
V_out
T_A
V_OE
TCV_OE
G
TCG
ε_G
ε_L(Θ_{P max})
: p rimary current linkage (At)
: max primary current linkage applied to the
transducer (At)
: output voltage (V)
: ambient operating temperature (°C)
: electrical offset current (V)
: temperature coefficient of V_OE (mV/K)
: sensitivity of the transducer (V/At)
: temperature coefficient of G (%/K)
: sensitivity error (%)
: linearity error for Θ_{P max} (%)
This model is valid for primary ampere-turns Θ_P between -Θ_{P max}
and +Θ_{P max} only.
Sensitivity and linearity
To measure sensitivity and linearity, the primary current (DC) is
cycled from 0 to I_P, then to -I_P and back to 0 (equally spaced
I_P/10 steps). The sensitivity G is defined as the slope of the linear
regression line for a cycle between ± I_PN.
The linearity error ε_L is the maximum positive or negative
difference between the measured points and the linear regression
line, expressed in % of I_PN.
Magnetic offset
The magnetic offset voltage V_OM is the consequence of a current
on the primary side (“memory effect” of the transducer’s ferro-
magnetic parts). It is measured using the following primary
current cycle. V_OM depends on the current value I_P1 (I_P1> I_PM).
V
= ^Vout
(t ) −V
1
out
(t₂ )
OM
2
I_P (DC)
I_P1
0A
t
-I_P1
t₂
t₁
Ip(3)
Ip(_t
3)
Figure 17: C urrent cycle used to measure magnetic and
electrical offset
(transducer supplied)
Electrical offset
The electrical offset voltage V_OE can either be measured when
the ferro-magnetic parts of the transducer are:
●● completely demagnetized, which is difficult to realize,
●● or in a known magnetization state, like in the current
cycle shown in figure 17.
Using the current cycle shown in figure 18, the electrical
V_OE
= ^Vout
(t
1
)
+
V_out
2
(t )
2
offset is:
Note: the
transduce^.r^..OT
(T ) =
has
.._t._OoE
(T ) −
be
..._dOEe(2_m5_a°C_g)_netized
prior
to
the application of the current cycle (for example with a
demagnetization tunnel).
Overall accuracy
The overall accuracy at 25 °C X_G is the error in the
- I_PN .. + I_PN range, relative to the rated value I_PN.
It includes:
●● the electrical offset V_OE/ Θ_P·G (%)
●● the sensitivity error ε_G (%)
●● the linearity error ε_L (to I_PN) (%)
Response and reaction times
The response time t_r and the reaction time t_ra are shown in
figure 18
Both depend on the primary current di/dt. They are measured
at nominal ampere-turns.
I
100 %
90 %
I_p
10 %
V_out
t_r
t_ra
t
18February2014/Version 3
Figure 18: Response time t_r and reaction time t_ra
Page 15/16
LEM reserves the right to carry out modifications on its transducers, in order to improve them, without prior notice
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