MAIN
CIRCUIT
Service Manual M4 - M10
29.12.1999
Page
69
8.3.3 Troubleshooting
In the case, that drive does not wake up within few seconds (delay depends on
size of the drive) when power is applied from supply line, precharging circuit
may be damaged.
Checking of the precharging resistors:
1.
Damage of the precharging resistor(s) can usually be found out by
visual checking due to designed characteristic at brake down.
2.
In the case of units above 90kW (frame sizes M8 and larger), to check
precharging resistors in each modules, it is recommended to check the
precharging resistors from terminals of each charging switches.
3.
Measure resistance value of the precharging resistor(s) cross charging
switch. Resistor is bypassing one phase of the charging switch. For the
proper connection refer to main circuit diagram of the particular type
of drive is under analyses.
4.
DMM in diode checking mode, measure threshold voltage of diodes in
two input phases cross terminals (L1) to (+DC) and (L3) to (+DC). Diodes
biased forward, the value of the voltage should be within range of
0,3...0,5V if resistor is not burned open. Phase (L1) is lead via charging
contactor and value should be infinite.
If charging switch will not be activated (pulled in) within few seconds from
connection to mains, procedure for trouble shooting of failing operations of
the charging switch are following:
1.
Check input phases for missing power. If power from the input phase,
from where charging switch is powered up is missing, the switch does
not have energy for coil to pull in (to close the contactor). Apply proper
input power for drive.
2.
Coil of the charging switch does not get control, even line is OK.
If voltage on all input phases is on, but above malfunction exists,
reason for the malfunction of the charging switch may be:
- Step down transformer is damaged, or circuit is open.
- Power supply is damaged, or loaded down due to excessive load
current in some of output lines. See troubleshooting of power supply
in section 9 (PC BOARDS).
3.
Coil is powered up, but the charging switch does not pull in. If the
charging switch does not follow control the cross the coil, internal
damage in the switch is very probable, or the switch is jammed
mechanically.