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"B" Group: Fine Tuning Functions Section 3-6
3-6-18 Carrier frequency (PWM) related
Carrier frequency adjustment: B083 – The internal switching frequency of
the inverter circuitry (also called the chopper frequency). It is called the carrier
frequency because the lower AC power frequency of the inverter "rides" the
carrier. The faint, high-pitched sound you hear when the inverter is in Run
Mode is characteristic of switching power supplies in general. The carrier fre-
quency is adjustable from 2.0kHz to 15kHz. The audible sound decreases at
the higher frequencies, but RFI noise and leakage current may be increased.
Refer to the specification derating curves in Chapter 1 to determine the maxi-
mum allowable carrier frequency setting for your particular inverter and envi-
ronmental conditions. Refer also to B089 for automatic carrier frequency
reduction.
Note The carrier frequency setting must stay within specified limits for inverter-
motor applications that must comply with particular regulatory agencies. For
example, European CE-approved application requires the carrier to be 3 kHz
or less.
Automatic carrier frequency reduction: B089 – The automatic carrier fre-
quency reduction 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).
When the output current
increases to 60%, 72%, 84%,
or 96% of the rated current,
this function reduces the car-
rier frequency to 12, 9, 6, or
3 kHz, respectively. This func-
tion restores the original carrier
frequency when the output
decreases to 5% lower than
each reduction start level.
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.
Note If 3 kHz or less freq. has been specified for b083, this function is disabled
regardless of the setting of b089.
[Remark: Above graph is for schematic concept and the profile is a subject to
change reflecting the temperature test.
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