Installation, Operation and Service Manual
LKP Series 4 Channel OEM
© 2019 DynAmp, LLC
Page 21
041593O
5.9 PULSE TRANSFORMER DRIVERS
The pulse transformer drivers consist of U203, U204, and associated circuitry. A pulse train
signal is sent into the drivers (pin 2 and 1 of U203 for channel #1). These drivers are open
collector outputs, which drive the pulse transformers (T203A and T203B for channel 1). The
secondary of the pulse transformer develops a current pulse which drives the associated SCRs
(SCR pack #1 for channel #1).
5.10 OUTPUT CIRCUIT
LKP Series 4 Channel OEM systems provide a dc current output that has a 5000:1 relationship
with bus current. The output circuit must be low impedance, and is connected to terminals TB1-
22 (positive) and TB1-23 (negative) of the Metering Unit.
Circuit impedance is calculated by dividing the burden voltage by the full-scale output current of
the measuring system. For example, a 10 kA metering system has a full-scale output current of
2 amperes (10 kA/5,000 turns), and the maximum impedance of the output circuit would be 7.5
ohms (15 V/2 A). For a 30 kA system, the output current of the output circuit would be 6
amperes and the maximum load would be 2.5 ohms.
Burden resistors inserted in series with the output circuit should be selected with care. The
wattage rating should be at least two times higher than the calculated power dissipation. The
burden resistor should have a low temperature coefficient (25 ppm or better).
5.11 ACCURACY DIAGNOSTICS (OPTIONAL)
“ACCURACY DIAGNOSTICS” (AD) is a system that assures the user that most internal circuits
are operating properly and it is also a diagnostic tool. It is made up of a number of circuits,
monitoring conditions of many of the critical components, circuits and connections within the
current monitoring system. The AD subsystem provides relay contacts for the user to connect
to this remote warning indicator. The AD diagnostic light emitting diodes on each Metering Unit
module indicate proper operation of associated circuits. On some larger systems a red warning
light mounted on the enclosure door provides a simple visual warning (refer to wiring diagram
for this feature).
The AD indicates the feedback circuits are functioning properly and the system’s power
supplies are within specifications. More specifically, this indicates the following conditions exist:
1. All channels have a core magnetic flux null:
a. All components in the circuits appear to be operating normally.
b. Input fields are of the expected polarity.
c. Input magnetic flux appears balanced by feedback flux.
2. Power supplies are operating within acceptable ranges.
a. Mains input power is on.
b. Hall plate sensor power supply output is correct.