8.11
Date Code 20090730 Instruction Manual SEL-734 Meter
Logic
Math Variables
Math Variables
Sixteen SELOGIC control equation math variables are available. SELOGIC
control equation math variables are math calculation storage results. Use the
MAT command to view the results of each math variable.
Use math variables in fixed-form programming to store the results of math
calculations as arguments in math calculations and comparisons. Available
math operators are plus (+), minus (–), multiply (*), and divide (\).
Example 8.1 illustrates SEL
OGIC control equation math variable usage.
Math variable analog quantities use secondary values
EXAMPLE 8.1 SELOGIC Control Equation Math Variables
The equations below show fixed-form SEL
OGIC control equation
programming examples that use SEL
OGIC control equation math
variables. Each line has a comment after the # that provides
additional description.
MV01 := 378.62 # Store 387.62 in MV01
MV09 := 5 + VA_MAG # Store sum of 5 and A-phase secondary
voltage in MV09
Math Error Detection
If a math operation results in an error, the SEL-734 turns on the math error bit,
MATHERR, in the Meter Word. A settings change or the STATUS SC
command provides reset for this bit. For example, if you attempt to divide a
value by zero, the math error bit will be asserted until you clear the bit with a
STATUS SC command or change settings.
Counter Variables
SELOGIC control equation counters are up- or down-counting elements, with a
reset input and two outputs:
➤ one asserts when the programmable count limit is reached
➤ the other asserts when the counter is at position zero
These counter elements conform to the standard counter function block #3 in
IEC 1131-3 First Edition 1993-03 International Standard for Programmable
Controllers - Part 3: Programming Languages.
Table 8.3 describes the Boolean input settings, counter value setting, and
Boolean outputs of the counters. Note that n = 01 to 16.
Table 8.3 Counter Inputs and Outputs (Sheet 1 of 2)
Name Type Description
SCnLD Load Preset Value Loads SCn, with SCnPV. This will assert SCnQU.
SCnPV Maximum Value Maximum number of counts that SCn will increment
before freezing.
SCnCU Count Up on Rising
Edge
Value that increments SCn up. Use any SEL
OGIC con-
trol equation setting or Meter Word bit.
SCnCD Count Down on
Rising Edge
Value that increments SCn down. Use any SEL
OGIC
control equation setting or Meter Word bit.
SCnR Counter Reset Logic that resets counter output value, SCn, to zero.
Courtesy of NationalSwitchgear.com
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