Efficient Networks Siemens Sinamics S120 - Manual (Page 179)

Drive Functions
Function Manual, (FH1), 07/2007 Edition, 6SL3097-2AB00-0BP4
179
Basic functions
6
6.1 Changing over units
Description
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 type plate of the drive converter 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
1200 RPM.
– If the reference speed is changed to 3000 RPM, then the value of 80% is kept and
now means 2400 RPM.
Restrictions
● When a unit changeover occurs, rounding to the decimal places is carried out. This can
lead to the original value being changed 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 values (p2000 to p2007) are changed offline in STARTER, it can lead to
boundary violations of the parameter values, which cause error messages during loading
to the drive.
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.