Transformer-Rectifier (T-R) Assembly - Hobart 60CU20 Operation And Maintenance Manual With Illustrated Parts List

OM-2226 / Operation and Maintenance Manual
60CU20 / Series 500062 / 400 Hz. Generator Set

11) Transformer-Rectifier (T-R) Assembly

The T-R provides a regulated output voltage of 28.5V DC. Input power is provided to the DC components
from the 115/200 volt, 400 Hz generator set, through an input contactor. The output contactor provides
DC power to the load. If during DC operation, AC power is required, the DC output voltage will no longer
be regulated once the AC output contactor is closed. The AC voltage regulator will take over regulating
the AC output voltage. The DC voltage will drop during full load applications when the simultaneous
operation is used.
a) Transformer Assembly (T401)
This transformer assembly steps down the generator's output (115/200 VAC, 3 phase, 400 Hz) to 25
VAC. The smaller voltage is rectified by the six diode rectifiers, located on the heat sink assembly.
b) Heat Sink / Diode Assembly (CR402-CR407)
This assembly rectifies the AC voltage from transformer assembly, providing unfiltered 28.5V DC. A
DC shunt connected to the heat sink assembly measures the DC output current.
c) Input Contactor (K401)
The input contactor applies the generator output power to the input of the transformer assembly.
d) Output Contactor (K402)
The output contactor connects the output of the 28.5 VDC power supply to the output cables. The
contactor is located on the right side under the T-R Assembly.
e) DC Inductor / Filter Assembly (L401)
The DC inductor filters the raw 28.5 VDC from the diode assembly and provides low ripple 28.5 VDC
output.
f) Pre-Load Resistors (R402-R404)
The three 10-ohm, 100-Watt pre-load resistors provide a minimum output load on the DC output.
g) Capacitor PC Board (A401)
The DC capacitor PC board works with the DC inductor as a filter to produce a low ripple 28.5 VDC
output voltage.
h) Control Interlock Kit (Optional)
This optional assembly is used for applications requiring a safety interlock signal being sent back
from the aircraft before closing the output contactor to delivery power to the load. See Chapter 4,
Section 3 for details of the assembly and Chapter 5 for schematics and connection diagrams.
May 2, 2013 Chapter 1-1
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