Eaton PowerXL DC1, Manual

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6 Parameters
6.2 Digital and analog inputs
DC1 Frequency Inverter 10/12 MN04020003Z-EN www.eaton.com
129
6.2.10.2 Speed behavior with slip compensation
In the control mode (V/Hz with slip compensation, P-10 > 0), the frequency
inverter can compensate for fluctuations caused by the load's characteristics.
To do this, the internal motor model uses the measured voltage and current
values of the stator winding (u
1
, i
1
) to calculate the required manipulated val-
ues for flux variable i
μ
and torque variable i
w
. In the three-phase motor's
equivalent circuit diagram, the load-related slip is shown as resistor R’
2
/s.
During no-load operation, this resistance approaches infinity, and approaches
zero as the load increases.
Figure 77: Equivalent circuit diagram for an asynchronous motor
① Stator winding
② Air gap
③ Transformed rotor winding
An exact calculation requires the precise rating specifications of the motor P-
07, P-08, P-09). The speed control P-10 > 0) can then compensate the load-
related slip deviations.
The simple illustration shows that, as the load torque increases ( ① ), the
resulting speed reduction is compensated by an increase in the output fre-
quency (
② ) ( ￫ Figure 78).
Figure 78: Speed behavior with slip compensation
R
1
a c b
X'
2
X
1
i
1
i
w
u
1
X
h
i
m
R'
2
s
M
M
2
M
1
n
1
n
a
b