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Servotronix has embedded field-
oriented, closed-loop control in its
stepIM integrated, stepper motors.
Figure 6. Servotronix’s stepIM with
closed-loop control The integrated
electronics control the stepper
motor as a two-phase BLDC
motor, implementing position loop,
velocity loop, DQ control, as well
as additional algorithms. Closed-
loop commutation, by means of
an absolute, single-turn encoder,
ensures optimal torque utilization
at any speed. Furthermore, closed-
loop stepper motors are less noisy
and vibrate less than open-loop
stepper motors. Let’s consider the
stepIM as our case.
Lower energy consumption and
keeping cool
StepIM stepper motors are efficient
consumers of energy. Unlike open-
loop steppers that are always
commanded with full current,
resulting in heat and acoustic noise,
current to the stepIM flows only
when needed, for example, during
acceleration and deceleration. Like
servos, these steppers consume
current proportionally to the
actual torque required at any
given moment. Since motor and
integrated electronics run cooler,
stepIM steppers can achieve the
higher peak-torque levels associated
with servos.
Close match to performance
requirements
To make sure that there is enough
torque to overcome disturbances
and to avoid losing steps, open-
loop steppers are routinely sized
with at least 40% more torque
than required by the application.
Not so with closed-loop stepIM
steppers. When these steppers
are overloaded to a stall condition,
they continue to hold against the
load without losing torque. Upon
removal of a blocking load, they
continue to run. Maximum torque
at any given speed is guaranteed
while position sensors ensure that
no steps are lost. Thus, closed-loop
steppers can be sized to closely
match the torque requirements of
their application without the 40%
extra margin.
Figure 4. A stepper’s torque decreases as its speed increases
Figure 5. Closed-loop technology advancements enable stepper
motors to step into high-performance, high-speed applications
formerly reserved for servos
Figure 6. Servotronix’s stepIM
with closed-loop control
New-Tech Magazine Europe l 25