Control Principle; Fc 300 Controls; Fc 301 Vs. Fc 302 Control Principle - Danfoss VLT AutomationDrive FC 300 Design Manual

FC 300 Design Guide

3.2.1. Control Principle

A frequency converter rectifies AC voltage from mains into DC voltage, after which this DC voltage
is converted into a AC current with a variable amplitude and frequency.
The motor is supplied with variable voltage / current and frequency, which enables infinitely var-
iable speed control of three-phased, standard AC motors and permanent magnet synchronous
motors.

3.2.2. FC 300 Controls

The frequency converter is capable of controlling either the speed or the torque on the motor
shaft. Setting par. 1-00 determines the type of control.
Speed control:
There are two types of speed control:
•
•
Selects which input to use as speed PID feedback in par. 7-00.
Torque control (FC 302 only):
Torque control is part of the motor control and correct settings of motor parameters are very
important. The accuracy and settling time of the torque control are determined from
motor feedback
•
Speed / torque reference:
The reference to these controls can either be a single refrence or be the sum of various references
including relatively scaled references. The handling of references is explained in detail later in this
section.

3.2.3. FC 301 vs. FC 302 Control Principle

FC 301 is a general purpose frequency converter for variable speed applications. The control prin-
ciple is based on Voltage Vector Control (VVC
FC 301 can handle asynchronous motors only.
The current sensing principle in FC 301 is based on current measurement in the DC link or motor
phase. The ground fault protection on the motor side is solved by a de-saturation circuit in the
IGBTs connected to the control board.
Short circuit behaviour on FC 301 depends on the current transducer in the positive DC link and
the desaturation protection with feedback from the 3 lower IGBT's and the brake.
Speed open loop control which does not require any feedback (sensorless).
Speed closed loop control in the form of a PID control that requires a speed feedback to
an input. A properly optimised speed closed loop control will have higher accuracy than
a speed open loop control.
Motor Control Principle
(par. 1-01
Flux with encoder feedback offers superior performance in all four quadrants and at all
motor speeds.
MG.33.B9.02 - VLT ® is a registered Danfoss trademark
3. Introduction to FC 300
).
plus ).
3
Flux with
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