Basic Functions; Switching Over Units - Siemens SINAMICS S120 Function Manual

Basic functions

7.1

Switching over units

By changing over the units, parameters and process quantities for input and output can be
changed over to an appropriate system of units (US units or as per unit quantities (%)).
The following supplementary conditions apply when changing over units:
● Parameters of the drive converter rating plate or the motor rating plate can be changed
over between SI/US units; however, a per unit representation is not possible.
● After changing over the units parameter, all parameters that are assigned to one of the
units group dependent on it, are all changed over to the new system of units.
● A parameter is available to select technological units (p0595) to represent technological
quantities in the technology controller.
● If the units are converted to per unit quantities and the reference quantity changed, the
percentage value entered in a parameter is not changed.
Example:
– A fixed speed of 80% corresponds, for a reference speed of 1500 RPM, to a value of
– If the reference speed is changed to 3000 RPM, then the value of 80% is kept and
Restrictions
● When a unit changeover occurs, rounding to the decimal places is carried out. This can
mean that the original value might change by up to one decimal place.
● If a referenced form is selected and the reference parameters (e.g. p2000) are changed
retrospectively, the referenced values of some of the control parameters are also
adjusted to ensure that the control behavior is unaffected.
● If the reference variables (p2000 to p2007) are changed offline in STARTER, there is a
risk that the parameter value ranges will be violated. In this case, appropriate fault
messages will be displayed when the parameters are loaded to the drive unit.
Groups of units
Every parameter that can be changed over is assigned to a units group, that, depending on
the group, can be changed over within certain limits.
This assignment and the unit groups can be read for each parameter in the parameter list in
the SINAMICS S120/S150 List Manual.
The unit groups can be individually switched using 4 parameters (p0100, p0349, p0505 and
p0595).
Drive functions
Function Manual, 11/2017, 6SL3097-4AB00-0BP5
1200 RPM.
now means 2400 RPM.
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