Current Control - Sanyo CMH1972A Technical & Service Manual

7-2-2. 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
Example of operation for heating
(20A)
(17A)
(16.6A)
Target
frequency
Frequency
•
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 appoximately 3 minutes later, if Point C is exceeded.
(May operate when sudden voltage fluctuations occur.
(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.
Point C (peak cut trip)
Point B (Hz reduction)
Point A (Hz increase prohibit)
NOTE During defrost operation, the COOL current setting value is used.
(2) Current control
The operating frequency upper limits shown in the figure below are established for frequency reduction and
increase-prohibit.
Current(A) Example of operation during cooling
Trip
Hz reduction
Hz increase
prohibit
(16)
(15.6)
0
(30)
Stops operation
Approx.3 minutes
(20A)
HEAT COOL
(20.0) (20.0)
(17.0) (17.0)
(16.6) (16.6)
Hz reduction
Hz increase prohibit
Hz reduction
Hz increase prohibit
Frequency (Hz)
Power Point C
Point B
Point A
Indicates trouble.)
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