Page 11 - Industrial Technology EXTRA 26th October 2020

a brushed DC ironless motor combined with a gearbox t o o i n s ®
and encoder; a brushless DC motor with a gearbox m a l p i t s c
and sometimes an encoder; or a stepper motor, either
direct drive or with a gearbox, and sometimes an
encoder where closed loop operation is desirable.

Brush DC motor technology
An ironless brush DC motor is a good fit for a battery-
operated portable pump application because it has no
iron losses and is therefore highly efficient. Indeed,
precious metal commutation allows motor efficiencies
up to 90%, while evolving magnet technologies
enable the motors to deliver high torque at a given
speed. Ironless motors also have a very low
inductance and a commutation with small contact
surface and pressure, resulting in a low electrical
resistance and very little friction.
The primary disadvantage of a brushed DC motor,
of course, is that its brushes will wear, and this is one
of the primary impactors on the lifespan on the
product. If lifespan is a decisive consideration, then
the design engineer may want to look instead at a
brushless DC (BLDC) motor for the infusion pump.

Brushless motor technology
In a BLDC motor the coils are fixed and the magnet is
part of the rotor. Commutation in the coils is done
electronically. Usually the external tube closing the
magnetic field of the magnet is fixed, generating iron
losses while the magnet is rotating. In applications
where inertia is not critical, the tube and the magnet
can rotate together, removing iron losses. The motion plastics effect: longer service life and a reduction
®
in costs ... and always at least one of the two: this is the
There are two categories of BLDC motor: slotless
goal of all igus products. Tribo-plastics for motion, efficient
®
and slotted. The slotless design has the advantage of production, and logistics, provide over 200,000 customers
®
with "cost down, life up" benefits. The igus range includes
no cogging or detent torque, while also having less
flexible energy supply systems with special dynamic cables,
iron loss than a slotted design and therefore higher and tribological engineering components such as plain
bearings, ball bearings, linear systems, 3D printed parts. All
efficiency. Where size is a primary consideration,
igus products are available ex stock, and the life can be easily
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advancing high energy magnets make slotless motors calculated online.
a good option.
Compared with a DC ironless motor, the BLDC
motor will have lower efficiency due to the iron losses,
plastics for longer life ®
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October 2020 • INDUSTRIAL TECHNOLOGY EXTRA • p11 igus Caswell Road Northampton NN4 7PW
Tel 01604 677240 sales@igus.co.uk