commutator bars. A corresponding V-
shaped ring, insulated with mica, holds
the commutator together. When clamped,
tension forms between the bars and rings,
drawing the commutator bars inwards.
When designing this mounting method, an
experienced designer allows enough bar
height to accommodate the v-notch without
weakening the bars.
A shallow V-notch, designed incorrectly, will
allow bars to lift in operation, which will lead
to a failure.
Glass-banded commutators are lighter in
weight and require less maintenance. The
segment pack compression is retained on
the exterior of the commutator by cured
glass banding applied in grooves adjacent to
the brush track.
These banded commutators, which lack
clamping, means they cannot be checked
for tightness in the same way as the dovetail
configuration. However, by tapping each
segment and listening out for the ‘ring,’
ensures the bars have remained rigid.
Steel shrink ring commutators are designed
for extreme duty applications and can
withstand rapid acceleration and high
speeds. The technique for shrinking-on is
more modern than that used for dovetailing.
The equipment is not usually repaired;
which is why PLD Collettori do not produce
them. Finally, before shipping the finished
commutators, several quality checks are
carried out resulting in an impressive 1.8 x
1000 production defect wastage.
Checks include: testing of dimensions,
insulation resistance with a dielectric or
hipot test, commutator hardness (Brinnel
Test), measuring resistance to mass, heat
seasoning of the commutator through
various operating cycles, and an over-speed
centrifuge test.
PLD Collettori sits comfortably in a niche
market, for which there is very little
competition in Europe.
Luciano takes great pride in the quality
of the work they produce and hasn’t
any concerns about the future of the DC
Commutator sector.
Although an aging technology, there
is plenty of room for business in other
countries.
The repair industry is becoming a large
revenue generator for the business now, so
their joining the AEMT network comes at a
strategic time.
Luciano and Dino’s partnership with Roberto
Movio and Nestech was formed after
exhibiting at CWIEME in 2013. Roberto was
representing a steel cutting company close
to PLD Collettori’s booth.
Molded commutators are typically smaller,
less expensive, for high series production. After getting to know one another better,
they realised there was a clear synergy in
their expertise and networks.
PECM Issue 33
Where the expanding companies go in the
future, is too early to say, but for now the
synergies and co-operation between these
two companies is working very well.
For enquiries, contact Dino or Roberto on
+39 0445 745097 or on email by
[email protected]. Their website can be
found at www.pldcollettori.it
Next for PLD Collettori
The copper alloy body, which is held
together by glass banding, is shrunk
into an insulated steel body to give a
single compact piece. This can reach high
rotational speeds, even for very long
commutators.
76
To support Roberto in the startup of
Nestech, has meant PLD can reduce their
overheads by sharing equipment, and
improve parts of their own steel lamination
production.
About the AEMT
The Association of Electrical and
Mechanical Trades (AEMT) was
founded in 1945. It is an International
Association representing leading
companies in the electrical and
mechanical service and repair
industry.
Members manufacture, distribute,
install, service, maintain, and repair,
electric motors, drives, pumps, fans,
gearboxes, generators, transformers,
switchgear, and ancillary equipment.
In addition to motor and pump
service facilities, most members
operate mechanical engineering
workshops for metal fabrication and
the repair and refurbishment of worn
components.