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

Basic functions

8.1

Switching over units

Function 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 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 a changeover is made to referenced variables and the reference variable is subsequently
changed, the % value entered in a parameter will not change.
Examples:
– 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 now
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 you change the reference variables (p2000 to p2007) offline, 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, 06/2019, 6SL3097-5AB00-0BP2
1200 RPM.
means 2400 RPM.
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