Application:
Control Panel for large Turbine engines
The
application called for a converter to be designed that would provide
a 5 volts output with 20 amps of current. The input range for the
system was 20 - 32 Vdc. In appearance a very simple task, 100 watts
of output with a routine input operating range of less than 2- 1.
Output accuracy for the application called for 4.87 - 5.25 max.
Unique
problems:
Solutions:
1)
100
% redundant operation upon customer request
Output
"OR"ing diodes on all units
2)
Load
Sharing/ paralleling required
Current
sensing each unit and feedback to the redundant unit with constant
current correction to maintain balance
3)
5
foot output cable to required load and regulated at far end
of cable
Remote
sense circuits at the load with provisions for IR loss down
5 feet of cable length
4)
Live
power "hot swapping" required
Inrush
limiting circuit with 3 second delayed start up
5)
Input
reverse polarity protection required
Input
forward voltage diodes to prevent reverse input voltage and
input shorts which causes loss of hold up time
6)
2
mili-second ride-thru before 20 mili-second hold up time
2
mili-second ride-thru of input power loss before alarming system
7)
No
air flow available, convection cooling only
Flat
Base Plate design for system bolt down
8)
Output
alarms and power on indicators needed
All
input/output signals monitored and alarmed
9)
Hazardous
Location application
CSA
Class 1 - Div. 2 certification
10)
Output
Over-voltage protection on single and on parallel operation
The converter must sense, at the far end of the cable, which
of the 2 units is in over-voltage and keep the good unit alive
and shut down the bad unit.
Monitoring
circuitry to sense each unit output voltage is done both at
the customer load point and before the internal "or"ing
diodes. These 2 measurements are then compared to determine
which unit is providing the out of tolerance voltage. The lower
voltage unit then sends a shutdown signal to the out of tolerance
unit, there-by keeping the system operational at all times and
preventing any system shutdown or damage.