Lenze 8400 TopLine - Manual (Page 161)

Lenze · 8400 TopLine · Reference manual · DMS 6.0 EN · 06/2014 · TD05/TD14
161
5 Motor control (MCTRL)
5.4 V/f characteristic control (VFCplus)
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5.4.2.1 Defining the V/f characteristic shape
In principle, four different characteristic shapes can be stipulated:
1. Linear V/f characteristic:
For drives for a constant, speed-independent load torque.
2. Quadratic V/f characteristic:
For drives with a load torque curve which is quadratic or in relation to speed. Quadratic V/f
characteristics are preferred in the case of centrifugal pumps and fan drives.
3. Freely definable V/f characteristic:
For drives that require adaptation of the magnetising current by means of the output speed. The
freely definable V/f characteristic can be used e.g. for operation in conjunction with special
machines such as reluctance motors in order to suppress oscillations at the machine or to
optimise energy consumption.
[5-3] Principle of a linear V/f characteristic (on the left) and a quadratic V/f characteristic (on the right)
4. Linear V/f characteristic with voltage reduction:
For drives which often work in partial load operation, the energy-saving V/f characteristic
control (VFCplusEco) offers the opportunity to reduce the voltage at low load in order to save
energy. At higher loads, the voltage reduction is cancelled and a linear characteristic is caused.
The V/f characteristic shape is defined by selecting the corresponding motor control mode in
C00006 :

Tip!
• You can find detailed information on freely definable V/f characteristics in the
subchapter entitled " Defining a user-defined V/f characteristic ". ( 172)
• You can find detailed information on the linear V/f characteristic with voltage reduction
in the chapter entitled " V/f characteristic control - energy-saving (VFCplusEco) ". ( 176)
0 1
0
100 %
N
n
n
U min
U
out
0 1
0
100 %
N
n
n
U min
U
out
V/f characteristic shape Motor control to be selected (C00006)
Linear V/f characteristic 6: VFCplus: V/f linear
Square-law V/f characteristic 8: VFCplus: V/f quadr
User-definable V/f characteristic 10: VFCplus: V/f definable
Linear V/f characteristic with voltage reduction 11: VFCplusEco: V/f energy-saving