A redundant PT input for PT
failure detection is possible, and
single-phase sensing can be
Number of Inputs
Volts or Current
EX2100 User's Guide GEH-6632
Power Potential Transformer Inputs
In the EX2100 excitation system, a 3-phase source of ac power is converted to a
controlled dc output. This ac input can be from one of several sources. Most
common is a generator terminal connected Y-Delta power potential transformer. The
primary and secondary voltages as well as kVA ratings are sized for the particular
application. An auxiliary bus fed PPT is also commonly used. In industrial
applications where forcing is needed for large motor starting a compound source
(current and voltage) input can be used. This ac input is connected to the bus in the
bridge cabinet and can be isolated by the 41AC1 device for maintenance. It is
monitored by the controls through the EACF board.
Potential and Current Transformer Inputs
Customer supplied 3-phase PT and CT are wired to switches in the control cabinet as
shown in Figure 4-1. The switches are wired to the EPCT. High frequency noise
suppression near the point of signal entry is provided on all input signals to EPCT.
On the board, the two 3-phase generator voltage inputs, nominal 115 V ac, are
brought into PT transformers. Two generator CTs (phases A and C), with either 1 A
or 5 A secondaries, are brought into CT transformers. The resulting low voltage
transformer output signals are cabled to the EMIO board in the control rack.
Generator Voltage Measurement
The cable lengths from the generator PTs can be up to 1000 ft of #12 AWG wire.
The PT secondary outputs are nominally 115 V rms at 50/60 Hz and are fused. On
EPCT, the two transformers make a three-wire open delta voltage measurement,
yielding 1.533 V rms for a 115 V rms input.
In the case of a simplex system the voltage signals are sent through the J305
connector to the EMIO board in the M1 controller. In the case of a redundant system,
the signals are fanned to connectors J305, J308, and J315, and sent to controllers M1,
M2, and C.
2, 3 phases each
10-200 V rms, 115 V rms nominal
50/60 Hz nominal
Less than 1 VA
Generator Current Measurement
Two generator current inputs from the CTs are wired to non-pluggable terminal
blocks, TB2 and TB3 that support ring terminals. The CTs do not have fused
secondaries. There is a choice of a 0-1 A rms CT input, or a 0-5 A rms CT input. The
cable length from the CT to the EPCT board can be up to 1000 ft., and the wire gage
can be up to #10 AWG. The resulting signals are sent to the EMIO board through the
same connectors as the voltage signals.
The EPCT board provides an analog input for customer use. This input is jumper
selectable for either ± 10 V dc or 4-20 mA. The EMIO samples the input at 2000
samples per second, and the accuracy is better than 1% full scale.
Chapter 4 Terminal Board I/O and Equipment Connections 4-3
2, Phases A and C
0-2 A, nominal 1A, or
0-10 A, nominal 5 A
50/60 Hz nominal
Circuit loading 6.25 VA nominal