12.10.3 Motor Protection
Motor derating frequency at low speed
This function is used to reduce the overload and thermal risks as motors have
worse cooling performance at low speed, compared at rated speed.
Code
Name
Setting range
Default
Min.
Attri.
C1.75 Low speed derating frequency
0.10...300.00
25.00
0.01
Run
C1.76 Zero speed load
25.0...100.0 %
25.0
0.1
Run
Fig. 12-46: Derating at low speed
●
Low speed derating frequency
When the output frequency is higher than [C1.75] 'Low speed derating fre-
quency', the allowed continuous current is [C1.07] 'Motor rated current'.
When the output frequency is lower than [C1.75], the allowed continuous cur-
rent is reduced according to the above curve, with the lowest value to [C1.76]
'Zero speed load' at standstill.
●
Zero speed load
Zero speed load is the allowed continuous current (percentage of rated cur-
rent) at standstill.
For a motor with external cooling, [C1.76] 'Zero speed load' is set to
100 %, and the low speed derating function is inactive.
VFC 3210
Bosch Rexroth AG
Functions and Parameters
DOK-RCON04-VFC3210****-IT01-EN-P
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