Power Meter Bulletin No. 3020IM9503R6/98
Appendix I—Alarm Setup December 1998
104 1998 Square D All Rights Reserved
APPENDIX I—ALARM SETUP (PM-650 ONLY)
INTRODUCTION
The power meter is designed to handle a wide range of metering require-
ments. To handle very large and very small metering values, the power meter
uses scale factors to act as multipliers. These scale factors range from 0.001 up
to 1000 and are expressed as powers of 10. For example, 0.001 = 10
–3
. These
scale factors are necessary because the power meter stores data in registers
which are limited to integer values between –32,767 and +32,767. When a
value is either larger than 32,767, or is a non-integer, it is expressed as an
integer in the range of ±32,767 associated with a multiplier in the range of 10
–3
to
10
3.
When POWERLOGIC application software is used to set up alarms, it
automatically scales pickup and dropout setpoints.
However, when alarm setup is performed from the power meter’s display,
you must:
• determine how the corresponding metering value is scaled, and
• take the scale factor into account when entering alarm pickup and dropout
settings
SCALING ALARM SETPOINTS
If you do not have POWERLOGIC software, you must set up alarms from the
power meter display. This section explains how to properly scale alarm
setpoints so you can do that.
The power meter displays the scale factor needed for the pickup and dropout
setpoints in the Alarm Setup mode. Only the pickup and dropout values
require scale factors. The pickup and dropout delays are entered in seconds.
After enabling an alarm, the next screen displayed is the scale factor for the
alarm pickup value. For example, when setting up an Under Frequency alarm,
the screen displays “Enter PU value in FREQUENCY x 100.” This means that
if you want to set a pickup value of 58 HZ, you must enter the pickup value as
5800. After you enter the pickup value and pickup delay, the next screen
displays the proper scaling of the dropout value. Enter the dropout value in
the same manner as the pickup value.
As another example, consider an Under Voltage Alarm. For a 480 V system,
you might want to enter the pickup value as 455 V. The screen may display
“Enter PU value in VOLTS x 1.” Therefore, you can enter the pickup value as
just 455 since the scale factor is 1.
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