Menu 5
80
Commander SK Advanced User Guide
www.controltechniques.com Issue Number: 9
This parameter contains the stator resistance of the machine for open loop vector mode operation.
If the drive cannot achieve the necessary current levels to measure the stator resistance during an auto-tune (e.g. there is no motor connected to the
drive) an rS trip will occur and the value in Pr
5.17
remains unchanged. If the necessary current levels can be achieved but the calculated resistance
exceeds the maximum allowable value for that particular drive size, an rS trip will occur and Pr
5.17
will contain the maximum allowable value.
This parameter defines the required switching frequency.
The drive may automatically reduce the actual switching frequency (without changing this parameter) if the power stage becomes too hot. The
switching frequency can reduce from 18kHz to 12kHz to 6kHz to 3kHz. An estimation of the IGBT junction temperature is made based on the heatsink
temperature and an instantaneous temperature drop using the drive output current and switching frequency. The estimated IGBT junction
temperature is displayed in Pr
7.34
.
If the temperature exceeds 135
o
C, the switching frequency is reduced if possible (i.e if the current switching frequency is >3kHz) and auto-switching
frequency change mode is enabled (see Pr
on page 82) to reduce the drives losses and thus reduce the IGBT junction temperature.
If the load condition persists, the junction temperature may continue to rise. If the temperature exceeds 145
o
C and the switching frequency cannot be
reduced the drive will initiate an O.ht1 trip.
Every 20ms the drive will attempt to restore the set switching frequency if the higher switching frequency will not take the IGBT temperature above
135
o
C.
Also refer to
The 18kHz switching frequency is not available on Commander SK size B and C, 400V units, Commander SK size D or Commander SK size 2 to 6.
Therefore it is not recommended to use these drives where the output frequencies are likely to be above 550 Hz.
With drive firmware V01.07.01 onwards, the 400V size C drive will have an actual switching frequency of 3kHz when the output frequency is below
6Hz.
With a default switching frequency of 3 kHz, the maximum output frequency should be limited to 250Hz. Ideally a minimum ration of 12:1 should be
maintained between the output frequency and the switching frequency. This ensures the number of switching per cycle is sufficient to ensure the
output waveform quality is maintained at a minimum level.
0
: OFF High stability space vector modulation disabled
1
: On High stability space vector modulation enabled
5.17
Stator resistance
Coding
Bit
SP
FI
DE Txt VM DP ND RA NC NV
PT
US RW BU PS
3
1
1
1
1
Range
0.000 to 65.000
Ω
Default
0.000
Second motor
parameter
Pr
Update rate
Background
5.18
Maximum switching frequency {37}
Coding
Bit
SP
FI
DE Txt VM DP ND RA NC NV
PT
US RW BU PS
1
1
1
1
1
Range
3(0), 6(1), 12(2), 18(3) kHz
Default
3(0)
Update rate
Background
Value
Display
Frequency (kHz)
0
3
3
1
6
6
2
12
12
3
18
18
5.19
High stability space vector modulation
Coding
Bit
SP
FI
DE Txt VM DP ND RA NC NV
PT
US RW BU PS
1
1
1
Range
OFF(0) or On(1)
Default
OFF(0)
Update rate
Background
NOTE
NOTE
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