NORDAC ON / ON+ (SK 3xxP) – Manual with installation instructions
48 BU 0800 en-4521
4.2 Selecting the operating mode for motor control
Motors from NORD are designed as asynchronous motors in efficiency classes IE1 to IE3, and IE4
and IE5 motors are designed as synchronous motors.
The NORDAC ON frequency inverter is able to control asynchronous motors with efficiency classes
IE1 to IE3. The NORDAC ON+ frequency inverter is able to control motors with efficiency class IE5+.
In terms of control technology, IE4 motor operation shows many special features. The frequency
inverter is designed for the control of IE4 and IE5 motors from NORD. In terms of structure, these IE4
motors match the type of an IPMSM (Interior Permanent Magnet Synchronous Motor). In these
motors, the permanent magnets are embedded in the rotor.
The operation of other manufacturer's motors must be checked by NORD, if required. Observe the
following additional information:
– IE4 synchronous motors: Technical information TI 80-0010 “Planning and Commissioning
Guideline for NORD IE4 Motors with NORD Frequency Inverters”.
– IE5 synchronous motors: Catalogue M5000 “Synchronous motors with IE5+ energy efficiency”.
4.2.1 Explanation of the operating modes (P300)
The frequency inverter provides different operating modes for the control of a motor. All operating
modes can be used with either an ASM (asynchronous motor) or a PMSM (Permanent Magnet
Synchronous Motor), however various constraints must be complied with. In principle, all these
methods are "flux oriented control methods.
1. VFC open-loop mode (P300, setting "0")
This operating mode is based on a voltage-governed flux oriented control method (Voltage Flux
Control Mode (VFC)). This is used for both ASMs as well as PMSMs. In association with the
operation of asynchronous motors this is often referred to as "ISD control".
Control is carried out without the use of encoders and exclusively on the basis of fixed parameters
and the measurement results of actual electrical values. No specific control parameter settings are
necessary for the use of this mode. However, parameterisation of the precise motor data is an
essential prerequisite for efficient operation.
As a special feature for the operation of an ASM there is also the possibility of control according to
a simple V/f characteristic curve. This mode of operation is important if several motors which are
not mechanically coupled are to be operated with a single frequency inverter, or if it is only possible
to determine the motor data in a comparatively imprecise manner.
Operation according to a V/f characteristic curve is only suitable for drive applications with relatively
low demands on the quality of speed control and dynamics (ramp times ≥ 1 s). For machines which
tend to have relatively large mechanical vibrations due to their construction, control according to a
V/f characteristic curve can also be advisable. Typically, V/f characteristic curves are used to
control fans, certain types of pump drives or agitators. Operation according to a V/f characteristic
curve is activated via parameters (P211) and (P212) (each set to "0").
2. CFC closed-loop – Mode (P300, setting “1”)
In comparison with setting “0” “VFC open-loop – Mode”, this is generally a control with current-
controlled field orientation (Current Flux Control). For this operating mode, which with ASM is
functionally identical to the designation previously listed under “servo control”, the use of an
encoder is mandatory. This way, the motor’s exact speed characteristics are recorded and included
in the calculation for the motor control. The determination of the rotor position is enabled by the
encoder, where for the operation of a PMSM the initial value of the rotor position must be
determined. This allows for a more precise and faster control of the drive.
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