7-2. Protective Functions
NOTE The numerical values such as temperature, frequency, time and current in parentheses are an example
of
7-2-1. Current Control
The operating current may rise as a result of causes including increasing 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 cooling capacity.
•Operation at normal capacity is restored when the cause of the current rise is eliminated.
Description of function |
| |
| Example of operation for cooling |
|
Current | (20A) | Power Point C |
(16.6A) | Point A | |
| (17A) | Point B |
| Target |
|
frequency |
| |
Frequency | Frequency |
|
| Stops operation |
|
| Approx.3 minutes |
|
•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. 
Indicates trouble.)
(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.
| (20A) |
| COOL |
|
|
Point C (peak cut trip) | (20.0) |
|
|
Point B (Hz reduction) | (17.0) |
|
|
Point A (Hz increase prohibit) | (16.6) |
|
|
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