Toshiba JKSSS Plus Series, Instruction Manual, Page: 102 / 106

JKSSS+ Series - 96
JKSSS+ Series 2.3 - 4.2KV
32. The gate and cathode leads are the white wires on the gate drive
board in the medium voltage cabinet. See drawing below.
33. If waveform is inverted, swap Oscilloscope connections for proper
polarity. Close the temporary Start switch and allow the test motor to
reach full speed.
34. Then verify all gating signals to each SCR (two gating signals on
every gate drive board). See drawing below for correct waveform.
35. Once the bad signal(s) are found; write down the location and call
the factory for further guidance.
Waveform is
the gating signal as
measured with an
ungrounded oscilloscope
at the gate to cathode
of the SCR. The
waveform should be 1.7
to 2msec off time and
approximately 1.5 to
3 Vdc. This signal is only
present at full conduction
or the motor is at speed.
Each SCR gating signal
should be checked
in accordance with the
low voltage test procedure.