9440300990 3-1
DECS-250 Power Inputs
3 • Power Inputs
Power is applied to two separate inputs: control power and operating power. The control power input
supplies power to an internal power supply that provides power for logic, protection, and control functions.
The power stage uses the operating power input as the source for the converted excitation power that it
applies to the field.
Control Power
Two inputs supply the DECS-250 with control power. One input accepts dc control power and the other
input accepts ac control power. The level of acceptable control power voltage is determined by the style
number. One of two levels is possible. Style Lxxxxxx indicates a nominal voltage of 24 or 48 Vdc and
accepts a voltage range of 16 to 60 Vdc. Style Cxxxxxx indicates a nominal voltage of 125 Vac/Vdc and
accepts a voltage range of 90 to 150 Vdc and 82 to 132 Vac (50/60 Hz). One input (either dc or ac) is
sufficient for operation but two inputs provide redundancy (for style Cxxxxxx only). When both control
power inputs are used, an isolation transformer is required for the ac input. DC control power is applied at
terminals BATT+ and BATT–. AC control power is applied at terminals L and N.
Operating Power
For redundant applications with a single-phase, 300 Hz Marathon
®
PMG, only one DECS-250 can be connected to the PMG at a time. In
redundant applications, a contactor should be used for each DECS-
250 power input or equipment damage may result.
If operating power exceeds 260 Vac, the connection must be
configured as L-N single-phase or equipment damage may result.
Operating power is applied at terminals A, B, and C. To achieve the desired level of excitation, the
appropriate operating power input voltage must be applied. Table 3-1 lists the acceptable operating
power voltage ranges for the DECS-250. The operating power frequency range for the DECS-250 is 50 to
500 hertz for all voltages.
Table 3-1. DECS-250 Operating Power Specifications
Desired Nominal
Excitation Power Voltage
Applied Operating
Power Voltage Range
100 to 139 Vac, or 125 Vdc
190 to 277 Vac, or 250 Vdc
Inrush Current Reduction Module (ICRM)
During DECS-250 power-up, the optional ICRM prevents damage to the DECS-250 by limiting inrush
current to a safe level. When operating power is applied to the DECS-250, the ICRM limits the inrush
current by adding a high level of resistance between the DECS-250 and the power source. Once the
inrush current subsides, the series resistance diminishes quickly to allow nominal, steady-state current
flow.
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