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

FC 300 Design Guide
Speed control:
There are two types of speed control:
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.
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 Flux
with motor feedback (par. 1-01 Motor Control Principle).
• Flux sensorless offers superior performance in all four quadrants at motor frequencies above 10 Hz.
Flux with encoder feedback offers superior performance in all four quadrants and at all motor speeds.
•
The "Flux with encoder feedb" mode requires that an encoder speed feedback signal
is present. Select which input to use in par. 1-02.
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.

FC 301 vs. FC 302 Control Principle

"
FC 301 is a general purpose frequency converter for variable speed applications. The control
principle is based on space Voltage Vector Control (VVC
FC 301 can handle asynchronous motors only.
The current sensing principle in FC 301 is based on sum current measurement in the DC link. The ground
fault protection on the motor side is solved by a de-saturation circuit in the IGBTs.
FC 302 is a high performance frequency converter for demanding applications. The
frequency converter can handle various kinds of motor control principles such as U/f special
motor mode, VVCplus or Flux Vector motor control.
FC 302 is able to handle Permanent Magnet Synchronous Motors (Brushless servo motors)
as well as normal squirrel cage asynchronous motors.
The current sensing principle in FC 302 is actually sensing the current in each motor phase. The advantage
of having a current transducer in each phase is to have full ground failure protection.
20
Introduction to FC 300
plus
MG.33.B4.02 - VLT is a registered Danfoss trademark
).