25
AC LINE AND MOTOR WIRING
The purpose of statically testing the input rectifiers is to rule out failures in these devices. Typically a
failure of an input rectifier will have caused the input line fuses to blow. It should also be noted that
blown input line fuses can also be a result of a shorted IGBT. Testing the inverter section as described
on page 26 will rule out short circuits in the IGBT's.
1.
Prior to making the test, it is necessary to verify that the three
input fuses (F1, F2, and F3) are good. If they are not, they must
be replaced before proceeding.
2.
Connect the positive (+) meter lead to terminal 89 (+VDC).
Connect the negative (–) meter lead to terminals 91 (R), 92 (S),
and 93 (T) in turn. Each reading should show open.
3.
Reverse the meter leads connecting the (–) lead to terminal 89
(+VDC) and the (+) lead to terminals 91 (R), 92 (S), and 93 (T) in
turn. Each reading should show a diode drop.
4.
Connect the positive (+) meter lead to terminal 88 (–VDC).
Connect the negative (–) meter lead to terminals 91 (R), 92 (S),
and 93 (T) in turn. Each reading should show a diode drop.
5.
Reverse the meter leads connecting the (–) lead to terminal 88
(–VDC) and the (+) lead to terminals 91 (R), 92 (S), and 93 (T) in
turn. Each reading should show open. Test is complete.
Incorrect readings indicate a faulty Input Rectifier. The rectifier at fault
can be identified by noting which terminal read incorrectly. Terminal 91
corresponds to U4, Terminal 92 to U5 and Terminal 93 to U6. The
modules are arranged in the unit from left to right, U4, U5, U6. See
Removal and Replacement Instructions on page 33.
96 97 98
89 88
TESTING THE
INPUT RECTIFIERS