BENSHAW RediStart EXEXMVRMX3 Series, User Manual

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8.9.8 Sequential SCR Gate Firing
The SCR gate outputs are fired sequentially in this test . This test is used to verify that the fiber optic gate driver cards are properly
connected and functional. The gate output LEDs must be monitored during this test to verify proper operation.
When the MX
3
is performing this test it will display the following;
This display will indicate a gate number from 1 to 6 in the order G6, G3, G5, G2, G4 and G1. The medium voltage starter uses series
SCR strings instead of a single SCR so each gate number indicates a series SCR string being fired in sequence. The firing pattern is
shown in the table below. Ensure that the starter steps through this sequence triggering the SCRs in the order shown below .
Watch the sequence of the gate LEDs while this test is operating. If the SCR gates are fired out of sequence than check the fiber optics
for improper installation.
Press [ENTER] pushbutton to move to the next BIST step.
z
NOTE: If the SCR gate indicators do not light in the proper sequence during this test then consult Benshaw. Do not attempt to
operate the starter as SCR damage will occur.
8.9.9 All SCR Gates Firing
The SCR gate outputs are all fired in this test. This test allows easy measurement of the gate voltages. The gate voltages can be measured
with a DC voltage meter or with an oscilloscope. The voltages should be between 0.5VDC and 2VDC when measured with a DC voltage
meter. Connect the positive lead to the white gate wire and the negative lead to the red gate wire to measure the gate waveform with an
oscilloscope. Use 2 volts per division and a 2 millisecond time scale. See the figure below for a sample voltage measurement using an
oscilloscope.
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8 - TROUBLESHOOTING & MAINTENANCE
BIST Mode
Gate
G ? On
Step
Display
Gates Fired
1 G6 Phase 1 - B, D, F, H, J, L
2 G3 Phase 1 - A, C, E, G, I, K
3 G5 Phase 2 - B, D, F, H, J, L
4 G2 Phase 2 - A, C, E, G, I, K
5 G4 Phase 3 - B, D, F, H, J, L
6 G1 Phase 3 - A, C, E, G, I, K
Table 19: Gate Firing Sequence
Figure 55: Gate voltage of a proper SCR