Page 12 - Industrial Technology EXTRA 26th October 2020

There are a number of different
stepper motor technologies, including
permanent magnet, hybrid and disc
magnet. For battery applications, disc
magnet technology is a good fit as it
carries lower inertia and lower iron losses
than other steppers, resulting in higher
efficiency.
For small, portable pumps, stepper
motors are a strong selection if they can
be used in full step mode at low speed,
and the detent torque is sufficient to
ensure no movement from outside forces.
For higher speeds, the design engineer
should consider whether the motor has to
run only intermittently or to operate
frequently. If the high-speed requirement
is only intermittent (for example for a
syringe change) then the motor can be
driven as a standard stepper. If the motor
needs to operate many times at high
speed, the efficiency can be increased by
closing the commutation loop with
position feedback like a standard servo
motor. In some applications, a stepper
solution with a gearbox may be the most
economical design, since no encoder is
and lower torque for the same size unit. One way to required. In addition, at stall position no energy will
compensate for the losses is to use the BLDC motor be needed if the detent torque is strong enough to
at higher speeds, taking into account this parameter maintain the position.
when selecting a gearbox. We can see then, when it comes to medical
devices such as infusion pumps, there is no single
Stepper motor technology motor technology that provides an ideal solution for
The final option is the stepper motor, which has the every application. In any given situation, each motor
strong advantage of having many stable positions choice will offer both advantages and
(steps) per revolution, so providing a high torque for disadvantages. Portescap offers a full range of
a given size compared with either the BLDC motor motors covering all of the primary technologies and
or brush DC motor. The disadvantage of a stepper, encourages design engineers to work with such a
however, is that it is not able to run at high speed, specialist in order to take into consideration the
due to the inductance combined with the entire system, and not just a part of it.
commutation frequency, and due to iron losses. www.portescap.com

October 2020 • INDUSTRIAL TECHNOLOGY EXTRA • p12