Large Commutator
Refurbishment
A Specialist Operation
S
everal industries - including
mining, steel, rail and
power generation - rely
on large motors equipped
with commutators to produce the
power required by their applications.
However, without precision
maintenance, these vital components
can become inefficient and eventually
fail. John Bird, Commutator Supervisor
at Sulzer’s Birmingham Service
Centre looks at the processes involved
in delivering a fully refurbished
commutator.
The first, and possibly most important
step, is communication with the
customer to ensure that all the
necessary information has been
received; especially the history of the
commutator, which will have a bearing
on the type of refurbishment to be
carried out. The best way to illustrate
the process is using an example that
was completed by Sulzer’s engineers
recently.
Initially the customer sent over a
set of drawings and asked for a
quote to reinsulate a 1.9m diameter
commutator that was used in the
steel industry. This is quite a common
task and involves dismantling the
component, cleaning and then reusing
the original copper plates with new
mica insulation.
The in-house commutator production
facility at Sulzer’s Birmingham Service
Centre is able to refurbish almost any
commutator or slip ring assembly and
Sulzer is the only facility capable of
building new Pollock commutators.
The design capability combined with
machining expertise and supported
by a dedicated team of experienced
engineers enables Sulzer to deliver
commutator and slip ring projects to
budget and on time.
To reinsulate or not?
When the job arrived in the workshop,
a previous Sulzer job number was
noticed on the component and the
records showed that it had already
been reinsulated once before. Sulzer
recommends that commutators are
only reinsulated once before being
rebuilt with new copper. This is
because the job requires an amount of
copper to be machined off the plates
and if this is done more than once it
can weaken the plate and may cause
cracking.
Based on the information available,
Sulzer advised the customer that
it would be better to completely
refurbish the commutator, including the
manufacture of new plates. Following
this advice, the customer agreed and
the project got underway.
The next step was to measure all of
the dimensions and compare them to
the original drawings and with Sulzer’s
own drawings from the previous
refurbishment job. This commutator
consisted of 816 copper bars and
816 mica segments that separate the
copper. Overall the component weighed
in at close to 4 tonnes.
Jig manufacture
For every job a jig is required to
arrange the copper bars and mica
segments in the correct shape. Since
this particular commutator had been
previously repaired by Sulzer, the
correct jig was already available. In the
more extreme cases a brand new jig
has to be manufactured by the Sulzer
workshop, such as the one that was