Current Input - Sensia INSTRUCT ESP Configuration Manual

ESP Switchboard Configuration via ESP Controller
The front-end voltage divider circuitry in the Power Analyzer Card converts the 120V to small signals, and the
3-phase measuring chip on the Power Analyzer Card measured the voltage values.
The PT input voltage is limited, the maximum voltage should be 120VAC. Additional Potential Transformer
exists in Switchboard HV cabinet to interface to high voltage systems as shown in
The PT inputs can be scaled to match external PTs and calibrated to account for transformer tolerance.
2.2

CURRENT INPUT

The Power Analyzer Card contains three AC current transformer (CT) inputs for the purpose of measuring
and monitoring 3-phase motor current. A proprietary current transformer burden module is required to
connect the external CT to the Power Analyzer Card. The monitored parameters are:
Table 2.2: Current Input Parameters
PARAMETERS
Overload
Underload
Rotation
Unbalance
Figure 2.1: PT Inputs Cascade to 4000VAC
Monitor condition where current exceeds a specified maximum
value. The three phase RMS average or each individual phase
RMS current is monitored for overload. Used to protect a system
from a failing motor or motor cable while still permitting a motor
start.
The overload alarm has a 15-point time curve associated with it.
The individual points in this curve can be edited for special
applications.
The set point is typically set to 15% higher than the motor running
current.
The alarm appears as OVERLOAD on the display
Monitor condition where current drops below a specified minimum
value. Used to indicate a motor is not efficiently pumping fluid or
has air locked.
The set point is typically set to 20% below the motor running
current.
The alarm appears as UNDERLOAD on the display.
This feature is shared with the voltage inputs. Monitoring of
rotation can be either voltage mode or current mode.
The alarm appears as ROTATION on the display.
Monitor condition where current A-B-C magnitude are no-longer
matched. The three phase RMS average is compared to the
individual phases to calculate unbalance.
The set point is typically set to 20%.
The alarm appears as C_UNBAL on the display
Section 2: Theory of Operations
Figure 2.1.
OPERATION
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