Hobart 6T28-600CL Operation And Maintenance Manual page 22

OM-2244 / Operation and Maintenance Manual
DCS-600 / Series 500082 / Solid State Transformer-Rectifiers
The 1 amp, F2 through F7 fuses (8, Figure 5) are located near the control board behind the left side
panel. These fuses are accessible by removing the top panel.
d) Control Transformer ( Figure 5 Item 6)
The small control transformer located on the interior panel (7, Figure 5) provides 115 V AC to the K1
(10, Figure 5) input contactor coil, input contactor light A (12, Figure 4), and S1 (10, Figure 4) input
contactor switch via the half amp F8 contactor fuse (located on the control transformer). This
transformer does not provide the 10A, 115 VAC auxiliary power.
WARNING
Electric shock can kill! Disconnect input power at the source to remove voltage to the
control transformer, input fuses and contactor.
e) Auxiliary Power Circuitry
The single-phase auxiliary power receptacle ( Figure 4 Item 5) has the same frequency as the
primary input voltage. It is protected by the F9 fuse ( Figure 4 Item 11), located on the front panel,
typically 10 Amperes. The auxiliary power circuitry is turned off whenever the primary contactor is
open or off. The auxiliary power winding is typically located on the middle leg (B phase) of the main
transformer. It provides power to the receptacle (5, Figure 4) and to the fan motor via the S4 fan turn-
on thermostat. The fan thermostat saves energy and reduces internal dust accumulation by allowing
the fan to run only when necessary to prevent overheating.
A "MOV" voltage surge suppressor, RV1 (6, Figure 4), is installed across the receptacle terminals to
reduce voltage surge problems to the load equipment and the power source.
f) Output Contactor Circuitry
Output contactor K2 ( Figure 5 Item 3) is operated by the output contactor ON-OFF switch S2 ( Figure
4 Item 11). Placing this switch momentarily in the TOP (spring-loaded) position turns the output
contactor ON, and placing it in the DOWN position turns the output contactor OFF.
The positive output lead is to be connected to the positive output terminal of the K2 contactor. The
negative output lead is to be connected to the R11 ammeter shunt. A small notch has been made in
the bottom of the right and left side panels to allow the output cable assembly to pass out either side.
The S5 normally-closed overload thermostat (18, Fig. 5) mounted on the main SCR rectifier heat sink
is designed to remove the output command signal whenever the heat sink temperature rise becomes
too high from overload, loss of cooling air flow, etc. The thermostat automatically resets on cool
down.
g) Output Filter Circuitry
The DC output voltage is smoothed (filtered) by an L-C filter made up of L1 iron core reactor (4,
Figure 5) carrying the output current to the load and the ripple current to the C15, C16, C17
capacitors (2, Figure 5) in parallel with the load terminals. The R2, R3, R4 bypass resistors (4, Figure
5) provide both a pre-load to the SCR devices and a safety discharge circuit for quickly discharging
the filter capacitors whenever the power supply is turned off.
Note: The 50 Hz. units have an additional capacitor in this circuit.
December 15, 2014 Chapter 1-1
Page 10