Saturation characteristic (SM)
6.2.13.1 Determination of the saturation characteristic
The adaptation can only compensate slow changes (like e.g. temperature effects).
If dynamic changes, such as the current-dependent saturation, shall also be taken
into account, a saturation characteristic must be defined.
Since real saturation characteristic is rarely supplied by the motor manufacturer,
the saturation can be defined from the data sheet values for no-load operation,
rated current and maximum current.
Data must be consistent
➢ The EMF value is often specified for 25°C, but the rated torque at
rated current is specified for e.g. 120°C. If the emf is strongly temper-
ature-dependent, temperature influences are interpreted as satura-
tion effects and falsify the torque display.
Alternatively, the saturation characteristic can be preset via the mo parameters.
Peak value of the linked EMF
Maximum current in % rated current
Max. torque in % rated torque
▪ dr14 "SM EMF“ is the EMF in no-load operation (current = 0).
▪ The EMF at rated current is calculated from dr03 and dr09.
▪ The EMF at maximum current is calculated from dr12 and dr11.
This calculation is only valid if the current-to torque data for Id=0 are specified and
no field weakening current is required for reaching the maximum torque.
The saturation must only be taken into account when the motor is driven so far into
saturation that, due to the strongly changed motor parameters, also the controllers
must be adjusted (=> Chapter 6.2.6 Current control) or the torque accuracy shall
be improved under load.
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