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14-4. Current Limiting Function
This is the function to limit output current within a range from 50 to 100% of the rated current of the PAC27. In case a pure metal heater or a
lamp heater, i.e., a load with large rush current is used, this function is employed to protect thyristor by limiting rush current or to limit load current
for some other purposes.
A delay in time is caused because output current is detected by a built-in CT and a phase-control angle of thyristor is controlled. Therefore, load
switching while being energized is not allowed.
Besides, when a shorter time is set for soft start, current limiting may not act in time against a heavy load of rush current. This function should be
used with more than 2 seconds of soft start time.
This function, working as a high limit, is different from the constant current control function which controls current. As the constant current control
controls output current, however, it makes the use of the current limiting function unnecessary.
Note:
Output power falls to such an extent that the load rate exceeds 100%. (Current is limited to a set value by lowering the output voltage.)
When the current limit setting device is removed, the limiting works at 0% of the rated current and no output is produced. If the instrument is
used without the current limit setting device, the control terminals (CL2) and (CL3) have to be short-circuited. Then, the limiting works at 100%
of the rating.
14-5. Rapid Fuse
This rapid fuse is for thyristor protection. In the case of short-circuiting of an energized load or erroneous operation while a transformer is in
use, the thyristor elements are unable to be protected in an electronic protective circuit but using a rapid fuse makes protection possible.
During its use, the FUSE monitor lamp lights and the fuse fuses when there is no output.
How to Replace Fuse:
Open the cover of the body (printed board case) (See 7-1.).
A microswitch to signal for fusing is attached to the fuse. Draw
out the microswitch and replace the fuse with a new one.
14-6. Various Power Adjusters (External Appearances and Mounting Sizes)
ʀ
Ratings
Lead wire:
1 m vinyl lead wire provided
Characteristics / resistance value:
B10kΩ
Scaled plate and knob:
One pc. each provided.
ʀ
External dimensions and mounting sizes
Rated current
Type of fuse
Fuse rating
20A
QSF023
32A
30A
QSF025
40A
45A
QSF035
63A
60A
QSF036
80A
80A
QSF037
160A
100A
QSF037
160A
ʷ
Type of fuse
ʷ
Name and scale
/ 0 to 100%
ʀ
External power adjuster
/ same as above
ʀ
Manual power adjuster
/ same as above
ʀ
High/low power adjuster
/ same as above
ʀ
Current limit setting device
/ 50 to 100%
