User Manual

Chapter 7 Explanation of Functions
7 - 67
7.8.7 Automatic carrier frequency reduction [b089]
- The automatic carrier frequency reduction function automatically reduces the carrier frequency according
to the increase in output current.
- To enable this function, specify "01" for automatic carrier frequency reduction selection (b089).
Item Function code Range of data Description
Automatic carrier
frequency reduction
b089 00/01/02
00: Disabled, 01: Enabled, depending
on the output current, 02: Enabled,
depending on the heat-sink temperature
- ex.) b089=01
When the output current increases to 60%, 72%, 84%, or 96% of the rated current, this function
reduces the carrier frequency to 12, 9, 6, or 3 kHz, respectively. This function restores the original
carrier frequency when the output current decreases to 5% lower than each reduction start level.
Carrier frequency reduction start level(Restoration level)
Carrier frequency after
reduction (kHz)
Current dependence
[b089=01]
Heat-sink temperture dependence
[b089=02]
Less than 60% of rated current Less than 45°C 15.0
60% (55%) of rated current 45°C(40°C) 12.0
72% (67%) of rated current 55°C(50°C) 9.0
84% (79%) of rated current 65°C(60°C) 6.0
96% (91%) of rated current 75°C(70°C) 3.0
- The rate of carrier frequency reduction is 2 kHz per second.
- The maximum limit of carrier frequency change by this function is the value specified for the carrier
frequency setting (b083); the minimum limit is 3 kHz. If 3 kHz or less frequency has been specified for
b083, this function is disabled regardless of the setting of b089.
15.0kHz
60%
Out
p
ut current
(
%
)
Carrier frequency
12.0kHz
9.0kHz
6.0kHz
3.0kHz
72% 84% 96%
0 10050
A
ction of b089 = 01
15.0kHz
Heat-sink temperture ( ℃ )
Carrier frequency
12.0kHz
9.0kHz
6.0kHz
3.0kHz
0 5040 60 70 80
A
ction of b089 = 02