Thermal Dynamics SIGNATURE PAK 1250XRTM, Руководство пользователя

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36
SERVICE
4.5 TEST PROCEDURES (continued)
E. Diode Check (continued)
Figure 4-F Contactor Input Wiring
3. To check capacitor C9 to be sure it is in the circuit, first
disconnect primary power to the system. The resistance
from wire 38 to wire 10 should be 2.5
ohms . The
resistance from wire 12 to the negative heatsink should
be 0 ohms. A quick check can be made on the capacitor
by using an ohmmeter in the Rx1000 position. Discon-
nect wires from one side of the capacitor and measure
across the capacitor. The reading should sweep up to
near 0 ohms, then gradually drop back if C9 is okay. If
shorted, the reading will remain near 0 ohms and C9
should be replaced.
4. Overheating of the diode can occur if air flow over the
heat sink is inadequate or if the diode is not properly
fastened to the heat sink. Check to see that the diodes
are torqued to 2.5 ft-lbs (3.4 Nm) and that a light film of
electrically conductive heatsink compound (this is a
white grease) is present between the diode and heat
sink. Check to be sure that air passages in and out of
the unit are not obstructed.
5. Diodes that are faulty at the time of manufacture are
difficult to diagnose. These usually fail in the first few
hours of operation. Before deciding that this was the
case, be sure to check out the other possibilities.
Check the open circuit voltage between the two heat sinks
of the main bridge rectifier. This should measure 240-250
vdc on a three-phase unit.
To adjust the spark gap setting, use allen wrench to loosen
the set screw on the top of the brass block until the elec-
trode can be moved. Adjust the electrode until the proper
0.030 in (.76 mm) gap is obtained. Secure the electrode by
tightening the set screw.
Transformer outputs to the main bridge from T1, T2, and
T3 are numbered 132-133, 132-134, and 133-134.
If any one of the main contactors has been removed or
replaced, check input wiring orientation. Make sure that
the wires are as follows:
F. Open Circuit Voltage
G. HF Spark Gap Setting
I. Main Contactor Wiring
H. Main Transformer Leads