Hitachi RAM-90QH5, Service Manual, Page: 43 / 83

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DESCRIPTION OF MAIN CIRCUIT OPERATION
MODEL RAM-90QH5
1. Power Circuit
Fig. 1-1
This circuit full-wave rectifies 220-240 AC applied between terminals L and N, and boosts it to a required
voltage with the active module, to create a DC voltage.
The voltage becomes 320-360V when the compressor is operated.
Main Parts
(1)
Intelligent Power module (IPM)
This is an inverter configuration module.
(2) Active module
The active filter, consisting of a reactor and
switching element, eliminates higher harmonic
components contained in the current
generated when the compressor is operated,
and improves the power-factor. Smoothing
capacitor smoothes voltage, which has been
rectified by diode stack and boosted at ACT
section.
(3) Diode stacks
These rectify the 220-240V AC from terminals
L and N to a DC power supply.
< Reference >
In case of IPM malfunction or defective connection:
Immediately after the compressor starts, it may
stop due to “abnormally low speed” IP error, etc.
In case of active module faulty or defective
connection:
Although the compressor continues to operate
normally, the power-factor will decrease, the
operation current will increase, and the overcurrent
breaker of the household power board will probably
activate.
< Reference >
If D25VB60 is faulty, the compressor may stop
due to “lp”, “abnormally low speed”, etc.
immediately after is starts, or it may not operate at
all because no DC voltage is generated between
the positive e and negative d terminals.
If diode bridge 1 is faulty, be aware that the 25A
fuse might also have blown.
If diode stack is faulty, DC voltage may be not
generated and the compressor may not operate
at all. Also, be aware that the 5A fuse might have
blown.