Mitsubishi Heavy Industries FDT28KXE6A Service Manual page 20

2) Initiation condition: When the detected current becomes following value.
① Within 2 minutes after starting operation of CM1 and CM2, the capacity control is done at the current safe value
for starting mentioned in a) and b)
② During capacity measurement mode, the capacity control is done at the current safe value for measurement mode
mentioned in a) and b)
a) The inverter primary current (Current safe 1): See following graph
(At starting and at measuring mode, the current safe value is the value (23.5A) at 35ºC of outdoor air tem-
perature)
30
25
20
15
10
b) The inverter secondary current (Current safe 2): 24A
(At starting and at measuring mode, the current safe values are same.)
* Both current safe values mentioned in a) and b) can be corrected by the code P21 of 7-segment input.
Correction value α = 3 to + 6 (0.5 interval)
Factory setting
3) Control contents
① The frequency of all compressors currently operating in the same refrigeration system will be decreased at every
one second by 2-steps (Current safe 1: first step, Current safe 2: second step). The compressor that receives cur-
rent safe control command first decreases the frequency and when its frequency is retaining at certain frequency,
such retained frequency information is transmitted to master unit.
② Master unit will send the command to all other operating compressors in same refrigeration system to decrease
frequency up to the same frequency as the first compressor reduced to according to the information of the first
compressor.
③ After the frequency is decreased, if the inverter current within the detection range is still above the current safe
value, the procedure ① will be repeated.
④ After the frequency is decreased, if the inverter current within the detection range is lower than the current safe
value, compressors will keep that frequency.
⑤ The minimum indicated frequency Ni by this control is 20Hz.
Example 1: In case of heat load zone 3 mentioned in Page 2, the operation of 20Hz×4 compressors is minimum (not
42Hz×4 mentioned in the table).
Example 2 : In case of heat load zone 2 mentioned in Page 2, the operation of 20Hz×2 compressors is minimum (not
42Hz×2 mentioned in the table).
23.5
22.3
19.7
35 39 43
Outdoor air temperature (°C)
α = 0
18
- -
16.2
11.2 11.2
47 50