Siemens MICROMASTER 420 User Manual

Page 147

Issue 07/04

3 Functions

MICROMASTER 420 Operating Instructions

6SE6400-5AA00-0BP0

147

3.21.1.2

V/f open-loop control with flux current control (FCC)

Parameter range:

P1300, P1333

Warnings -
Faults -
Function chart number:

An improved current measurement function has been
developed for our MICROMASTER drive inverters. This
permits the output current to be precisely determined referred
to the motor voltage. This measurement guarantees that the
output current is sub-divided into a load component and a flux
component. Using this sub-division, the motor flux can be
controlled and can be appropriately adapted and optimized in-
line with the prevailing conditions.
FCC operation is only activated after the FCC starting
frequency P1333 has been exceeded. The FCC starting frequency P1333 is
entered as a percentage to the rated motor frequency P0310. For a rated motor
frequency of 50 Hz and a factory setting of P1333 = 10 %, this results in an FCC
starting frequency of 5 Hz. The FCC starting frequency may not be selected too
low as this has a negative impact on the control characteristics and can result in
oscillation and system instability.
The "V/f with FCC" control type (P1300 = 1) has proven itself in many applications.
It has the following advantages with respect to the standard V/f control:

Higher motor efficiency

Improved stabilizing characteristics

♦ →

higher dynamic response

♦ →

improved behavior to disturbances / control

total

flux

load