ABB PSTX 570 - Test the SCR

50 Service PSTX720...840 | Service Manual | 1SFC13105M0201
3.8.1 Test the SCR
IMPORTANT NOTE
Only perform the SCR-test if the
Softstarter displays one of the following
commandos: “Short circuit fault” or
“Open circuit thyristor fault”.
Replace SCR if the result of the test
shows under 1 Mohm.
DISMANTLE THE SOFTSTARTER
Remove main power cables and control
cables
Disconnect the main power cables and the control
cables as described in chapter 3.3.3, step 1-3.
1. Remove HMI cover
1
Loosen (1x) Torx 15 M3,5x12 from the HMI
bracket.
2
Loosen (4x) Torx 20 M4x12. Remove the
HMI cover by lifting it upwards from unit. Ensure
that screws do not come loose and fall down on
the PCBA upon removal.
3
Lift out the PCBA from unit (at this point still
mounted on bracket) to facilitate continued service.
2. Disconnect SCR cables from PCBA
Mark the SCR cables with 1, 2, 3 prior to
disconnecting them to ensure proper re-
connection. Note that markings are to be made
in accordance with existing data available on the
PCBA bracket.
1
Disconnect the three SCR cables from their
terminals on the PCBA using a long-nose plier.
2
Pull out the three SCR cables from the cable
inlets on the PCBA bracket.
3. Connect Megger to Softstarter
1
Connect the black megger contact to the main
terminal 1L1 on the Softstarter.
2
Connect the red megger contact to the main
terminal 2T1 on the Softstarter.
3
Set the megger on 500V. Press and hold the
Test button. Note the result.
Also use 500V for 690V softstarters.
Tx 20
M4 x 12
Tx 15
M3,5 x 12
1
3.8.1_1
2
1
3
2
3.8.1_2
1
2
1000V
500V
M
OFF
250V
M
1000V
500V
M
OFF
250V
3
3.8.1_3
3
2
1
3