Scr Testing - Powertronix Quasar Service Manual

Test Procedures

7.8.5 - SCR Testing

The UPS use two types of SCR devices, one to switch the reserve bypass and inverter output
to the load. The second type to connect the battery to the primary DC bus in the event of failure of the
utility supply.
The two different types of device used to perform these functions are both of twin pack construction how
ever S7 and S8 have a single SCR and Diode. arrangement.
Table 7-10 SCR
SCR S1 S2 S3 S4 S5
S6
SCR S7 S8
Failure of a static switch or battery SCR will initiate the appropriate indication on the LED display and
will normally fail open circuit O/C or short circuit S/C. If a faulty device is suspected it can be checked
using a DVM. A short circuit across the anode cathode junction will be quickly apparent, however an
open circuit cannot so easily be diagnosed as the high resistance indicated is the normal state of the
device when turned off.
The Gate Cathode resistance can also be measured and should be in the range of 10 to 20 ohms for
a serviceable SCR, a high resistance would indicate an open circuit.
It is therefore recommended that a functional test of the SCR is carried out using the simple test circuits
shown in Figure 7 12 and
Twin Pack SCR Replacement (S1 S2 S3 S4 S5 S6)
Note: Note SCR S6 has the gate drive leads reversed blue to 4 red to 6.
Table 7-11 SCR Gate Drive Lead Connection
SCR fitting is the reverse of the removal procedure refer to
tion.
7 - 22
Circuit Ref.
SEMIKRON SKKT 92/12E
SEMIKRON SKKH132/12E
Figure 7
1. Power down the UPS and carry out the DC bus discharge routine.
2. Gain access to the UPS power section by removing the top and side covers.
3. Disconnect and remove the Inverter driver/feedback PCB Part NºOSDE0071. Follow the
procedure on page 7
4. Remove the two SCR gate drive leads from terminals 4 and 6 from each SCR and note their
position.
5. Remove the terminal standoffs and screws to release the bus bars from SCR terminals 1. 2
and 3.
6. Disconnect the second gate drive leads from SCR terminals 1 and 2.
7. Remove the two SCR Allen retaining screws from each SCR and lift from the Heatsink
8. Carry out the following functional test on each SCR and replace if required.
SCR Type
132A combined SCR &
14.
32.
SCR
4
S1 Blue
S2 Red
S3 Blue
S4 Red
S5 Blue
S6 Blue
Service Manual
Part Nº
91A Twin Pack 0CASR212420
0CASR212132
Diode Pack
Gate Drive Terminal
6 1
Red Black
Blue Brown
Red Black
Blue Brown
Red Black
Red Black
12. for correct SCR gate drive connector loca
Issue 2 - November 2001
2
Brown
Black
Brown
Black
Brown
Brown
3x3 UPS