10.2 Torque Characteristics - Siemens SIMATIC SIMOSTEP 1FL3041 Functional Description

02.05

10.2 Torque characteristics

Load inertia
Elements of the torque
characteristic
M = Max. torque at max.
Bm
slew stepping rate
M = Load torque
L
f = Control frequency
s
f = Starting limit frequency
Am
f = Max. starting frequency
Aom
f = Max. operating frequency
Bom
J = Load inertia
L
Figure 10-1 Elements of the torque characteristic
© Siemens AG 1998 All Rights Reserved
FM-STEPDRIVE/SIMOSTEP (FB)
The maximum torque at maximum slew stepping rate M
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
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 (start/stop characteristic): Without load, the motor can start
Am
at the maximum starting frequency f
frequency is reduced.
The size of the starting range also depends on the load inertia J
by the load on the motor shaft. With J
characteristic shifts towards lower frequencies. The start/stop
characteristic shows the maximum starting frequency f
the load inertia J . If a load inertia and a load torque are present at the
L
same time, the starting limit frequency f
start/stop characteristic in the torque diagram in parallel to the left until
the maximum starting frequency f
in the J diagram (see figure).
L
Start-stop
(J > 0)
L
M
L
J
L
10 Stepping motor parameters and characteristics
; with a load, the starting
Aom
increasing, the start/stop
L
is determined by moving the
Am
corresponds to the one determined
Aom
M
Start-stop
(J = 0)
L
f f f
Am Aom Aom
of a stepping
Bm
can be output
Bm
exerted
L
as a function of
Aom
Bm
f f [Hz]
Bom s
n[r.p.m.]
f [Hz]
s
n[r.p.m.]
10-3