SIEMENS
5/6
Siemens D 15.1 · 2017
Engineering Information
Control overview
5
■
Mode of operation
(continued)
Protection against excessive drive losses
The protection against excessive drive losses uses the drive
losses to protect the drive against "high impedance" faults. The
drive losses are calculated as the difference between the
measured input and output powers – and are compared with
reference losses. Once the threshold is exceeded, a fault is
issued and the drive trips.
If, in the idle state, the drive losses exceed the idle threshold by
between 1 and 2 %, the control will issue a command to open the
input breaker within 250 ms. This fast response time will signifi-
cantly reduce the negative impact of a "high impedance" fault on
the drive system.
Speed and torque control
Note:
We recommend vector control for applications that require
speeds below 1 % with a high load torque. In cases such as
these a motor that has high full-load slip (> 1.0 %) and high
breakdown torque should be selected.
Feature
V/f control
Vector con-
trol without
encoder
Vector con-
trol
Speed range
(for 100 % holding torque
and 150 % starting torque)
40:1
100:1
200:1
Torque control
(as % of the rated torque)
-/-
± 2 %
± 2 %
Torque linearity
(as % of the rated torque)
-/-
± 5 %
< ± 5 %
Torque response
1)
-/-
> 750 rad/s
> 750 rad/s
Speed control
(as % of the rated speed)
Motor slip
± 0.5 %
2)
± 0.1 %
3)
Speed response
4)
20 rad/s
20 rad/s
> 20 rad/s
5)
Torque pulsation
(as % of the rated torque)
without overmodulation
6)
< 1.0 %
< 1.0 %
< 1.0 %
Torque pulsation
(as % of the rated torque)
with overmodulation
6)
< 3.5 %
< 3.5 %
< 3.5 %
1)
Torque response values apply for drives without output filter. Tuning may
be required to achieve these values.
2)
A speed error of -0.3 % is typical. Worst-case speed error is equal to
approx. 30 % of the rated motor slip.
3)
0.1 % can be achieved with a 1024 ppr encoder. Speed accuracy
depends on the encoder ppr (pulses per revolution).
4)
Speed response values apply as long as the torque limit is not reached.
5)
Testing is required to determine exact value.
6)
When SINAMICS PERFECT HARMONY GH180 drives are not operated
with overmodulation, they exhibit torque pulsations of less than 1 %
(see
the table above)
. Torque pulsation at the 6th harmonic frequency is higher
for drives operated in the overmodulation mode. This frequency only
occurs in the speed range from 95 up to 100 % of the rated speed. Torque
pulsations at all other harmonic frequencies are below 1 % of rated torque.
Refer to pages 5/7, 5/8 for more information on the rated cell voltage and
drive output voltage for which overmodulation is possible.
© Siemens AG 2017