Siemens 1FL3041-0AC31-0BJ0, Functional Description

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02.05 10 Stepping motor parameters and characteristics
© Siemens AG 1998 All Rights Reserved
FM-STEPDRIVE/SIMOSTEP (FB)
10-3
10.2 Torque characteristics
The maximum torque at maximum slew stepping rate M
Bm
of a stepping
motor depends on its type size, on the type of electrical control and, in
particular, on the stepping frequency. This relationship is specified as a
characteristic curve for each stepping motor system.
The maximum torque at maximum slew stepping rate M
Bm
can be output
by the motor at low stepping frequencies; the higher the stepping
frequency, the lower the maximum torque at maximum slew stepping
rate.
The operating range of the motor given by the maximum torque at
maximum slew stepping rate is divided into the starting range and the
acceleration range. In the starting range, the motor is able to follow a
suddenly activated or interrupted control frequency without a stepping
error; in the acceleration range, the control frequency may only be
changed gradually (frequency ramp) in order to prevent the motor from
losing synchronicity.
The starting range is limited by the characteristic curve of the starting limit
frequency f
Am
(start/stop characteristic): Without load, the motor can start
at the maximum starting frequency f
Aom
; with a load, the starting
frequency is reduced.
Load inertia The size of the starting range also depends on the load inertia J
L
exerted
by the load on the motor shaft. With J
L
increasing, the start/stop
characteristic shifts towards lower frequencies. The start/stop
characteristic shows the maximum starting frequency f
Aom
as a function of
the load inertia J
L
. If a load inertia and a load torque are present at the
same time, the starting limit frequency f
Am
is determined by moving the
start/stop characteristic in the torque diagram in parallel to the left until
the maximum starting frequency f
Aom
corresponds to the one determined
in the J
L
diagram (see figure).
Start-stop
(J > 0)
L
M
Bm
Start-stop
(J = 0)
L
f
Am
f
Aom
f
Bom
f
Aom
f [Hz]
n[r.p.m.]
s
f [Hz]
n[r.p.m.]
s
M
L
J
L
T
o
rque
Load inertia
Figure 10-1 Elements of the torque characteristic
Elements of the torque
characteristic
M
Bm
= Max. torque at max.
slew stepping rate
M
L
= Load torque
f
s
= Control frequency
f
Am
= Starting limit frequency
f
Aom
= Max. starting frequency
f
Bom
= Max. operating frequency
J
L
= Load inertia