Bulletin No. 3020IM9503R6/98 Power Meter
December 1998 Chapter 8—Metering Capabilities
1998 Square D All Rights Reserved 65
KYZ PULSE OUTPUT
This section describes the power meter’s pulse output capability. For wiring
instructions, see Chapter 5—Wiring. The KYZ output is a Form-C contact
with a maximum rating of 96 mA.
Calculating the Pulse Constant
This section shows an example of how to calculate the pulse constant (in this
case, a watthour-per-pulse value). To calculate this value, first determine the
highest kW value you can expect and the required pulse rate. In this example,
the following assumptions are made:
• The metered load should not exceed 1500 kW.
• The KYZ pulses should come in at about two pulses per second at full
scale.
Step 1: Translate 1500 kW load into kWH/second.
(1500 kW) (1 Hr) = 1500 kWH
(1500 kWH) = “X” kWH
1 hour 1 second
(1500 kWH) = “X” kWH
3600 seconds 1 second
X = 1500/3600 = 0.4167 kWH/second
Step 2: Calculate the kWH required per pulse.
0.4167 kWH/second = 0.2084 kWH/pulse
2 pulses/second
Step 3: Round to the nearest hundredth, since the power meter accepts
0.01 kWH increments.
Ke = 0.21 kWH/pulse
Summary:
• 3-wire basis—0.21 kWH/pulse will provide approximately 2 pulses per
second at full scale.
• 2-wire basis—0.11 kWH/pulse will provide approximately 2 pulses per
second at full scale. (To convert to the kWH/pulse required on a 2-wire
basis, divide Ke by 2. This is necessary since the power meter Form-C relay
generates two pulses—KY and KZ—for every pulse that is counted on a
2-wire basis.)
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