18
8-2. Current Control
●
The operating current may rise as a result of causes
including increasing heating or cooling loads or
decreases in power voltage. In these cases, the
operating frequency is automatically reduced, or
operation is stopped, in order to control the operating
current so that it is 20 A or less.
As a result:
• Power breakers and fuses will not be tripped.
• Operation can continue during this period with
somewhat reduced heating or cooling capacity.
• Operation at normal capacity is restored when the
cause of the current rise is eliminated.
Description of function
8-3. Low Start Current
Operation starts at 10 Hz, and the start current is less than
the normal operating current. This prevents the flickering of
fluorescent lights or television screens that occurs when
ordinary A/C units start.
8-4. Compressor Temperature Control
To protect the compressor coil from overheating, the
operating frequency is controlled based on the compressor
discharge temperature.
8-5. Outdoor Fan Control
8-5-1. COOL operation
8-2-1. Automatic frequency control
The operating frequency is reduced automatically, or
operation is stopped, in order to control the operating
current so that it is at or below the values shown in the
table below.
8-2-2. Current control
The operating frequency upper limits shown in the figure
below are established for frequency reduction and
increase-prohibit.
Example of operation for heating
Example of operation during cooling
• Operates at the target frequency at Point A and below.
• Stops increases to the frequency between Points A and B.
• Reduces the frequency by 1 Hz per 0.5 seconds when Point B is exceeded.
• Stops operation, and restarts it approximately 3 minutes later, if Point C is
exceeded.
(May operate when sudden voltage fluctuations occur.
→
Indicates trouble.)
Current
Frequency
Target
frequency
Power Point C
Point B
Point A
Frequency
Stops operation
Approx. 3 minutes
22.5A
13.0A
12.6A
Frequency (Hz)
Current (A)
Hz reduction
Hz increase prohibit
Hz increase prohibit
Hz reduction
Trip
Hz reduction
Hz increase
prohibit
0
10.1
10.5
30
Point C (peak cut trip)
22.5
22.5
Point B (Hz reduction)
13.0
14.0
Point A (Hz increase prohibit)
12.6
13.6
NOTE: During defrost operation, the COOL current
setting value is used.
HEAT
20A
COOL
Compressor discharge temperature
(
°
C)
5Hz every 30 sec. reduction
2Hz every 30 sec. reduction
(Hz reduction)
Increase
prohibit range
No control
Trip
90
100
106
110
Outdoor air temperature
Maintain previous status
Fan L
Fan H
Fan H
Fan H
Fan H
35 Hz or above
Less than 35 Hz
35 Hz
Frequency
31
°
C
29
°
C
*
Within the increase-prohibit range, the range changes
to the Hz reduction range (2 Hz every 30 seconds) if
the compressor temperature rises by 2
°
C.
