Gate Pulse Test Setup ? 

Whenever fuses or SCRs fail, a complete gate pulse test must be performed before putting power to the drive system.  The phase references must be available to allow complete gating system tests, and a procedure has been developed.  See Silcomatic Drawing 206B3927 Sheet OE for a system one-line diagram. 

The motor isolation switch must be left open and the Limit Amp contactor 112 must be left open for these tests.  The phase reference voltages are provided through the P.T.s as the 110VAC, 3 Phase Control Power to Silcomatic.  To arrange for this to be done safely the following steps should be taken:

1. Verify that the machine is at or below turning gear speed (2 RPM).
2. Turn Limit Amp Key Switch ?B? to SAFE position and remove key.
3. Open Limit Amp fused disconnect, and remove lockout key. See [123-777] (49A,32)
4. Turn off Kramerstat control power circuit breaker MCCA [3I} See [123-777](19-1)
5. Turn off Silco+ Rectifier control power MCCB [1G] See [123-777](19-20)
6. Install a jumper between terminals (7) and (8) of relay [MY] in Limit Amp 112 control cabinet. This jumper is related to the high-speed trip of the DC breaker.  See [206B1359] (501K)
7. In the Silcomatic 120 controller cabinet check to assure that process control signals at terminals TBCL - 11D, (5C40) and 17D are de-energized, then note wire color, disconnect and tape.  See [206B1359] (501J)
8. Substitute precision voltage source at TBCL - 11D,(5C40) and 17D input.? Initially
?set the voltage source to -2.77 VDC.? This should fully retard the gates.
9. Using differential probe connect phase reference for oscilloscope measurements to TB2-1 (positive lead) and TB2-16 (negative lead) of the 28V power supply.  0 is defined as the point where main AC power on the SCR stacks line 1 to line 3 first goes positive.  Voltage measured from TB2 PT1 to TB2 PT16 is in phase with main AC power line 1 to 3.  See drawing [206B1359]  (501F).
10. Connect a digital meter to test point RE on Silcomatic controller chassis front panel.  See drawing 206B1359 Sheet 501J.  This should give the input from the precision voltage source.
11. Connect digital meter to Silcomatic card cage backplane 0G pin 27.  This monitors the output of the preamplifier.  See drawing 206B1359 Sheet 501J.
12. Connect digital meter to test point EC on Silcomatic controller chassis front panel.  See drawing 206B1359 Sheet 501M.  This is the input to the Pulse Generator Board.
13. Hook current probe to SCR Bridge #1 SCR 1F gate signal and use to compare to phase reference to firing time of gate for SCR 1F when gates are turned on.  See Drawing 206B1359 Sheets P and Q.
14. Before starting the system, the gates will be blocked and the test points RE, 0G-27 and EC will have the readings shown in the Firing Angle Range and Shift at Various Demand Setpoints spreadsheet.  After starting the system, the precision voltage source should be set to the levels shown in the table in the RE column.  At each level the voltmeter readings at RE, 0G pin 27 and EC should be recorded.  The delay should be measured on the scope from the zero crossing of the phase reference to the first gate pulse after and this should be recorded.  The associated phase shift should be calculated from this number  and recorded.  The Phase shift equals (Delay from 0 Deg. Of Line 1-3 Phase Reference in milliseconds) divided by (16.67 milliseconds/cycle) times (360 degrees/cycle).  All values should be close to those shown in the spreadsheet.  In addition, full advance at 24.7V on RE was observed to be 0 degrees as expected.  Gates block at ?3.2V on RE and ?6.5 on EC.
15. Turn on Kramerstat control power circuit breaker MCCA [3I]
16. Turn on Silco+ Rectifier control power circuit breaker MCCB [1G]
17. Close Limit Amp fused disconnect switch.
18. Check with co-workers to assure ready for test before continuing procedure.
19. In Silcomatic Control Cabinet 120, Reset (I) Fault and Depress button, PBR.
20. In Silcomatic Control Cabinet 120 close Inverter DC Breaker.
21. Install jumper between terminals (32E) and (33E) in Limit Amp control cabinet.  By installing this jumper the drive system "thinks" that the Limit Amp contactor is closed, enabling the Drive System controls to function normally.  See [206B3927] [1C]
22. The Drive start button on Kramerstet 111 control panel should now be illuminated (green) enabling the Drive to start.
23. At this point in the procedure the gate pulses should be "active".
24.  Check to make sure that all of the gate pulses are working at the gate leads to the SCRs.  Compare their amplitudes, peak currents, rise times, average currents and pulse lengths.  These should be the roughly the same.  Any that are not should be investigated thoroughly to determine if the associated SCRs fires.  This can be done in conjunction with reading the phase differences among all gate pulses at a retard and advance value.  See the Gate Spacing Check at 0 Volts Setpoint and Gate Spacing Check at 12.34 Volts Setpoint spreadsheets for typical values.  All values shown in the spreadsheet should be recorded for the ongoing tests and compared to the spreadsheet typical values.  The phase shift and gate spacing should be very close to the values in the spreadsheets.  On the typical spreadsheets, the Expected Shift is calculated using the first pulse shift measurement and adding 60 degrees to get the second one and then adding 60 degrees to that one and so on.  The difference is the Phase Shift  minus the Expected Shift.  Note that all gate pulses must be working properly before reapplying power to the inverter.
25. Once the tests are completed follow the remaining procedure to remove jumpers and restore Drive system to normal.
26. Remove jumper between terminals (32E)and (33E) in Limit Amp control cabinet.
27. Open Limit Amp fused disconnect switch.
28. Turn off Kramerstat control power circuit breaker MCCA [3I]
29. Turn off Silco+Rectifier control power MCCB [1G]
30. Remove jumper from terminal (7) and (8) of MY relay in Limit Amp 112 control.
31. Remove all test equipment and test leads from test points and secure bridge doors.
32. Disconnect precision voltage source from TBCL ? 11D, (5C40) and 17D in the Silcomatic 120 controller cabinet.  Reconnect process control signals at terminals TBCL - 11D, (5C40) and 17D.  See [206B1359] (501J). Secure controller cabinet doors.
33. Install Limit Amp key switch "B" to safe position.  
34. At this point the system is back to normal

              Firing Angle Range and Shift at Various Demand Setpoints

RE
Board OG Pin 27
EC
Delay,0 Deg. Line 1-3 Phase Ref.
Phase Shift
Notes
(Volts)
(Volts)
(Volts)
(milliseconds)
(Degrees
?
0
-0.041
-6.89
?
?
Gates Blocked
-2.77
-0.375
-6.27
8.68
187.488
Gate Ena., Ret Limit
-1.6
-0.697
-5.73
7.96
171.936
Gate Ena.
-1.25
-0.79
-5.56
7.8
168.48
Gate Ena.
0
-1.135
-4.99
7.4
159.84
Gate Ena.
1
-1.4
-4.52
7.12
153.792
Gate Ena.
2
-1.682
-4.06
6.84
147.744
Gate Ena.
5
-2.503
-2.66
6.16
133.056
Gate Ena.
8
-3.323
-1.26
5.56
120.096
Gate Ena.
10
-3.87
-0.34
5.16
111.456
Gate Ena.
10.5
-4
-0.105
5.08
109.728
Gate Ena.
12
-4.42
0.588
4.38
94.608
Gate Ena.
12.34
-4.51
0.75
4.3
92.88
Gate Ena., Adv Limit
?
?
?
?
?
?

Gate Spacing Check at 0Volts Setpoint
RE
EC
SCR #
Bank
Delay,0 Deg. Line 1-3 Phase Ref.
Phase Shift
Notes
Exp. Shift
Diff.
(Volts)
(Volts)
?
?
(milliseconds) Measured with Scope
(Degrees)
?
(Degrees)
(Deg)
0
-4.99
1
1
7.0
150.3
Gate Ena.
150.3
0.0
0
-4.99
2
1
9.7
210.0
Gate Ena.
210.3
-0.4
0
-4.99
3
1
12.5
269.6
Gate Ena.
270.0
-0.4
0
-4.99
4
1
15.2
329.2
Gate Ena.
329.6
-0.4
0
-4.99
5
1
18.0
388.8
Gate Ena.
389.2
-0.4
0
-4.99
6
1
20.8
450.1
Gate Ena.
448.8
1.3
0
-4.99
1
2
7.0
152.1
Gate Ena.
152.1
0.0
0
-4.99
2
2
9.8
212.5
Gate Ena.
212.1
0.5
0
-4.99
3
2
12.6
272.2
Gate Ena.
272.5
-0.4
0
-4.99
4
2
15.4
331.8
Gate Ena.
332.2
-0.4
0
-4.99
5
2
18.1
391.4
Gate Ena.
391.8
-0.4
0
-4.99
6
2
20.9
451.9
Gate Ena.
451.4
0.5

Gate Spacing Check at 12.34 Volts Setpoint
RE
EC
SCR #
Bank
Delay,0 Deg. Line 1-3 Phase Ref.
Phase Shift
Notes
Exp. Shift
Diff.
(Volts)
(Volts)
?
?
(milliseconds)  Measured with Scope
(Degrees)
?
(Degrees)
(Deg.)
12.34
0.737
1
1
4.3
93.3
Gate Ena.
93.3
0.0
12.34
0.737
2
1
7.0
152.1
Gate Ena.
153.3
-1.2
12.34
0.737
3
1
9.9
213.4
Gate Ena.
212.1
1.3
12.34
0.737
4
1
12.6
273.0
Gate Ena.
273.4
-0.4
12.34
0.737
5
1
15.4
333.5
Gate Ena.
333.0
0.5
12.34
0.737
6
1
18.2
393.1
Gate Ena.
393.5
-0.4
12.34
0.737
1
2
4.3
93.3
Gate Ena.
93.3
0.0
12.34
0.737
2
2
7.1
152.9
Gate Ena.
153.3
-0.4
12.34
0.737
3
2
9.8
212.5
Gate Ena.
212.9
-0.4
12.34
0.737
4
2
12.6
273.0
Gate Ena.
272.5
0.5
12.34
0.737
5
2
15.4
333.5
Gate Ena.
333.0
0.5
12.34
0.737
6
2
18.2
393.1
Gate Ena.
393.5
-0.4