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Implementing a power-on-demand concept based on variable speed drives allows for energy saving in any application
that involves pumps or hydraulic systems. And when used in combination with an intelligent wiring and communication system, relevant machine data can also be easily recorded
- the basis for comprehensive power management.
Beginning with this initial installment , and with the gracious permission of ABB/Baldor Electric, we are
pleased to announce the beginning of a new series -- Baldor Basics: Motors. This is a collection of basicsdriven,
motor-intensive articles authored by former Baldor engineer Edward Cowern, PE, a respected
name by many in the electric motor industry. During his tenure at Baldor, Cowern - now enjoying his
retirement - was tasked with producing a number of motor- and basics-related tutorials, primarily in
response to a steady flow of customer questions regarding motors. Today's customers continue to ask
questions and seek answers to address their various motor-related issues. As with Cowern's original
introduction to the series, we hope you find these articles useful and would appreciate any comments or
thoughts you might have for future improvements, corrections or topics.
If you’re an electrical engineer
you know how an electric motor works; if
you aren’t, it can be extremely
confusing. Therefore, here’s the simplified explanation (or the “how
an electric motor works for dummies” version) of how a four-pole, three-phase
AC induction motor works in a car.
I was invited by Tom Astrene of TLT to write a response to the
July 2010 TLT article (Ref. 1). My rebuttal — “In Search of a Fatigue
Limit: A Critique of ISO Standard 281:2007” — was published
in Tribology and Lubrication Engineering, TLT, August
2010 edition (Ref. 10). While this article is also available online,
I will attempt to summarize the essence of my response.
Until now the estimation of rolling bearing life has been based on engineering models that consider an
equivalent stress, originated beneath the contact surface, that is applied to the stressed volume of the
rolling contact. Through the years, fatigue surface–originated failures, resulting from reduced lubrication or
contamination, have been incorporated into the estimation of the bearing life by applying a penalty to the
overall equivalent stress of the rolling contact. Due to this simplification, the accounting of some specific
failure modes originated directly at the surface of the rolling contact can be challenging. In the present
article, this issue is addressed by developing a general approach for rolling contact life in which the surfaceoriginated
damage is explicitly formulated into the basic fatigue equations of the rolling contact. This is
achieved by introducing a function to describe surface-originated failures and coupling it with the traditional,
subsurface-originated fatigue risk of the rolling contact. The article presents the fundamental theory of the
new model and its general behavior. The ability of the present general method to provide an account for
the surface–subsurface competing fatigue mechanisms taking place in rolling bearings is discussed with
reference to endurance testing data.
For the lubrication of open gear drives
used in different industrial applications
such as cement and coal mills,
rotary furnaces, or where the sealing
conditions are difficult, semi-fluid
greases are often used in preference to
fluid oils. For girth gear applications
the greases are used with a splash or
spray lubrication system. The selection
of such greases influences pitting lifetime
and the load-carrying capacity of
the gears, as well as wear behavior
Slow speed operation of fan systems within the air handling
industry is generally performed due to two reasons: a coast
down operation is required for hot (induced draft) fans to
cool down before shutdown (often by using a turning gear),
and operational efficiency improvements can be achieved
during non-peak periods by slow speed operation using a
VFD. In either case, when these fans are supported by hydrodynamic
bearings, it is the oil film thickness developed from
the bearing-shaft interaction that limits the minimum speed
that can be maintained without causing premature wear and
bearing failure. This paper will present a brief overview of
lubrication theory and critical design parameters to achieve
slow speed operation.
In order to analyze the different gear
oils suitable for the lubrication of wind turbine gearboxes, five fully formulated ISO VG 320 gear oils were selected. In between the selected gear oils, four PAO base oils can be found: PAOR, PAOM, PAOC and PAOX. A mineral-based oil (MINR) was also included as reference.
conveying system on the varnishing
line for a manufacturer of high-end
kitchen cabinets were leaking. Oil was
dripping on the cabinet parts — ruining
the finish. Why were half of the
gearboxes leaking?
Standard carburizing steel 18CrNiMo7-6 is often used when high hardenability is required, but due to its highly fluctuating price, there has always been an incentive to develop Ni-free steel grades. The 23MnCrMo5-5-2 — or Jomasco 23mod — has been developed for
this purpose. But to ensure smooth substitution within existing production lines, a number of points must be addressed: first, checking the response to carburizing treatments;
and second, having similar mechanical properties with identical tooth root bending performance on gears. The latter is the purpose of this paper.