Mitsubishi Heavy Industries FDT28KXE6A Service Manual page 13

(3) Starting control of the compressor (Master unit/Slave unit)
According to the elapsed time after power ON and to the number of start-up, the starting control method of compressor is
shown in following table. However during the defrost control, oil return control and oil equalization control, the starting control
method of compressor is depended on that of the each control.
① The 1st startup after 45minutes or more has elapsed since
power ON, or the subsequent startup after the
compressor has been stopping for 45 minutes or longer
with keeping the power ON.
② The 1st startup after less than 45 minutes has elasped
since power ON
③ The startup other than ① and ② mentioned above.
(a) 4-way valve switching safeguard (Master unit/Slave unit)
At starting, the inverter compressor (CM1, CM2) is operated under following conditions regardless of the decision frequency.
(i) 0-20Hz operation
It is operated in the range of 0-20Hz. However during this operation, the compressor protective controls like current safe
control, high pressure control, discharge pipe temperature control, low pressure control, power transistor temperature control,
under-dome temperature control and compression ratio protective control are not performed.
(ii) 25-40(48)Hz opearation
The maximum frequency is determined by the temperature detected with the outdoor air temperature thermistor (Tho-A).
1) In case of 0°C or lower of Tho-A: It starts to increase the frequency up to 48Hz as maximum frequency and
when the frequency reaches 48Hz, it stops.
2) In case of higher than 0°C of Tho-A: It starts to increase the frequency up to 40Hz as maximum frequency and.
when the frequency reaches 40Hz, it stops. However during this operation, if the starting conditions of the com-
pressor protective controls like current safe control, high pressure control, discharge pipe temperature control,
low pressure control, power transistor temperature control, under-dome temperature control or compression ratio
protective control is satisfied, this control ends and it is controlled according to such protective control satisfied
with. And if the compressor frequency is determined and this protective control is cancelled, it returns to the nor-
mal operation.
(b) Compressor protective start control (Master unit/Slave unit)
The compressor frequency is controlled regardless of the target frequency.
1) Up to 1minutes 45 seconds after the compressor starts, it is operated at 20Hz.
2) When 1minutes 45 seconds has elapsed after the compressor starts, it is operated at the frequency by compressor
potective start control.
(c) Compressor protective start control "A" according to the crankcase heater ON time (Master unit/Slave
unit)
If it is the 1st startup after 45 minutes of the cumulative crankcase heater ON time has elapsed since power ON or if it is
the subsequent startup after the compressor has stopped for 45 minutes or more since power ON, it starts operation accord-
ing to this control.
1) After 4-way valve switching safeguard, inverter frequency is set at 20Hz. And during reducing frequency to 20Hz
after 4-way valve switching safeguard, if the time for reaching to 20Hz is elasped 1 minutes after startup, it is set at
the maximum frequency after 1 minute elasped (20Hz+5Hz).
2) During the period of 15 minutes after the inverter frequency reaches to 10Hz (the frequency to complete startup), the
maximum inverter frequency will be increased from 20Hz by 5Hz per minute.
3) If the compressor stops within the period of 15 minutes after startup, and when the compressor starts again, the maxi-
mum inverter frequency is increased from 20Hz by 5Hz per minute during the cumlative period of 15 minutes under
this control after the initial startup.
Conditions Starting method
After 4-way valve switching safeguard, "compressor
protective start control A" will be perfomed according to the
crankcase heater ON time. (See followings)
After 4-way valve switching safeguard, "compressor
protective start control B" will be perfomed according to the
crankcase heater ON time. (See next page)
After 4-way valve switching safeguard, "compressor
protective start controls" will be perfomed.
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