Entity parameters example, Maximum input current (i, Or i – Rockwell Automation 1797-XXX FLEX Ex System Certification Reference Manual User Manual
Page 6: Maximum internal capacitance (c, Maximum internal inductance (l, And l, Also, the sum of all the u, And i, Cannot exceed the input u, 30v • i
Publication 1797-6.5.6 - June 2005
Preface 2
• maximum input current (I
i
or I
max
)
• maximum internal capacitance (C
i
)
• maximum internal inductance (L
i
)
In use, the sum of all the input C
i
and L
i
in a control loop cannot exceed the
C
o
and L
o.
Also, the sum of all the U
o
and I
o
cannot exceed the input U
i
and I
i
.
The following is a short explanation of how entity-based architectures help
simplify IS system design.
Entity Parameters Example
An output channel and the valve it will drive are illustrated in the following
figure. By comparing entity parameters, you can quickly determine the
appropriate match.
In this example, the combination is compatible because the valve can
withstand:
• U
i
= 30V
• I
i
= 165mA
These values are higher than what the 1797-IE8 can provide:
40052
cable length = 10m
268
Ω
21V
22
Ω
+
sig
C
i
<10pF/m
L
i
<0.5uH/m
R<0.1
Ω/m
P/I transmitter
EEx ia IIC T4
U
i
=30V
I
i
=165mA
C
i
=22.5nF
L
i
=730uH
Module
U
o
I
o
C
a
L
a
< or =
< or =
> or =
> or =
Total Loop
U
i
I
i
C
i
L
i
=
=
=
=
Transmitter
U
i
I
i
C
i
L
i
Distance
Cable
+
+
(length
*
C
i
per length)
(length
*
L
a
per length)
Module
U
o
<23.7V
I
o
<92.5mA
C
a
=66nF
L
a
=2.5mH
< or =
< or =
> or =
> or =
Total Loop
U
i
=30V
I
i
=165mA
C
i
=22.6nF
L
i
=735uH
=
=
=
=
Transmitter
U
i
=30V
I
i
=165mA
C
i
=22.5nF
L
i
=730uH
Distance
Cable
+
+
(10m
*
C
i
=10pF/m)
(10m
*
L
a
=0.5uH/m)
1797-IE8 Analog Input
EEx ia/ib IIB/IIC T4
U
o
<23.7V
I
o
<93.5mA
IIB
C
a
=560nF
L
a
=10mH
IIC
C
a
=66nF
L
a
=2.5mH