Commissioning
Optimising the operating behaviour
Slip compensation
6
6.11
6.11.1
6.11-2
EDSVF9333V EN 3.0-06/2005
V/fcharacteristiccontrol
The slip compensation (C0021) is automatically calculated from the rated
motor speed (C0087) and the rated m otor frequency (C0089). The entered
slip constant [%] is the rated slip of the motor in [%] relating to the
synchronous speed of the motor.
ƒ Calculating the slip compensation and entering it into C0021:
s =
n
rsyn
− n
r
n
rsyn
⋅ 100 %
n
rsyn
=
f
r
⋅ 60
p
E Slip constant (C0021) [%]
n
rsyn
Synchronous motor speed [min
-1
]
n
r
Rated motor speed according to
motor nameplate [min
-1
]
f
r
Rated motor frequency according to
motor nameplate [Hz]
p Number of motor pole pairs
(1,2,3,...)
ƒ If required, the slip compensation can be adapted manually:
– If C0021 is set too high, the drive may get unstable.
– With cyclic load impulses (e. g. centrifugal pump) a smooth motor
characteristic is achieved by smaller values in C0021 (possibly
negative values)
– Parameterise C0078 (filter time for the slip compensation) if you
want to change the motor response time to load changes
(dynamic ↔ slow).
ƒ The actual speed is output as an analog signal (in [%] of n
max
(C0011))
to MCTRL-NACT.
Note!
When operating synchronous or reluctance motors, C0021 must
be set to 0.
Vector control
Use C0021 to change the influence of the rotor resistance (C0082)
proportionally:
ƒ Reduce the value in C0021 at an increasing speed (negative values)
ƒ Increase the value in C0021 at a decreasing speed
Note!
When setting the vector control mode, the slip compensation
(C0021) is automatically set to 0.0 %.
ƒ When you switch back to the V/f characteristic control mode,
the slip compensation must be re-adapted.
Adjustment
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