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Industrial Work Solenoid Construction and Basic
Operation
A typical industrial work solenoid consists of the following
main elements: a cylindrical coil, a steel or iron frame or
shell, a steel or iron plunger and optionally, a stationary
magnetic pole/travel stop. A magnetic field is generated
within the industrial work solenoid by passing electrical
current through the coil. The frame or shell surrounds the
coil, providing a flux path. In effect, it focuses the
magnetic field produced by the coil. The plunger, being made
of highly magnetic material, reacts to the magnetic field by
attempting to move to the center of the coil. The plunger
will travel to the centered position unless stopped by a
load which exceeds the industrial work solenoid's force
capability or the plunger contacts the stationary
pole/travel stop.
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DC
Industrial Work Solenoid Operation Specifics
The force generated by an industrial work solenoid is
dependant upon the current flowing though the coil windings.
The average current in the coil of a DC industrial work
solenoid is the simple result of average source voltage
divided by the resistance of the coil.
DC industrial work solenoids may be powered from pure DC
sources such as batteries or electronic power supplies, or
from time varying sources so long as the source is single
polarity. The most common time varying sources are rectified
AC and Pulse Width Modulation (PWM) type electronic
controls. When powered from a time varying source, current
flows in proportion to the average value of the source
voltage. The force developed by the industrial work solenoid
is thus dependant upon the average value of the source
voltage.
Because the current in the coil of a DC industrial work
solenoid never reverses, the magnetic field never reverses
either. In most cases the current and therefore the magnetic
field is nearly constant. This is a significant factor in
the design and construction of DC industrial work solenoids.
The contrasting situation is an AC industrial work solenoid
in which the current and resultant magnetic field are
constantly reversing direction. This field reversal results
in significant losses in the metal structure unless
stringent precautionary steps are taken during design and
fabrication. Without getting into details, it is sufficient
to say that the design of AC industrial work solenoids
requires dealing with significant constraints on the
configuration of the metal components. DC industrial work
solenoids avoid these constraints, allowing use of common
wrought steels in their construction.
Because the metal components of a DC industrial work
solenoid can be fabricated from wrought steel, standard
machining and metal forming processes can shape individual
components. The basic performance of the industrial work
solenoid force developed versus plunger position, can be
influenced dramatically by shaping the plunger and
stationary pole face in particular. By using advanced
analysis tools like magnetic finite element analysis (FEA)
coupled with industrial work solenoid design experience, the
shape of the metal components of the solenoid can be
developed to yield optimum performance for any specified
application.
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DC
Industrial Work Solenoid Application
Considerations
Industrial work solenoids can be designed to accept
attachment of the load to the pulling or pushing end of the
plunger. For some applications the plunger assembly is
designed to accept load attachments at both ends.
Properly
designed and applied, a linear industrial work solenoid will
generate forces sufficient to move the applied load through
the specified stroke and in the specified period of time. It
must do so under all specified operating conditions. The
Industrial Work Solenoid Selection Guidelines section is
provided to assist you in developing your application
specifications
There are several issues that must be considered when any
customer application is being reviewed.
The method of connecting the load to the industrial work
solenoid must be developed with consideration in mind that
side loads will be detrimental to industrial work solenoid
life if not properly accounted for. Furthermore, if the
installation causes a binding condition anywhere within the
required operating stroke, excessive wear and reduced
operating life will result.
Industrial work solenoid holding force typically suffers
dramatically if the plunger is not allowed to come into
contact with the stationary pole piece. If the industrial
work solenoid will be required to generate a sustained
holding force after it has moved the load through its
working stroke, then, it most likely will be a requirement
that the plunger seat itself is at the end of travel as
opposed to being stopped by the load. There are exceptions
to this general rule. They must be dealt with through detail
application and design analysis.
Excessive force can cause its own set of problems. If under
any operating conditions, the industrial work solenoid
generates forces far in excess of what is required to move
the load, then there will be excess kinetic energy developed
in the plunger as it accelerates through its stroke. This
excess kinetic energy needs to be dissipated in a manner
that is not harmful to the industrial work solenoid or the
mechanism it is driving. Trombetta can provide application
assistance in evaluating and dealing with such
situations.
Electronic controls often make practical what otherwise may
not be a practical application. In other cases they can
serve to optimize the design of the total system through
shaping or stabilizing the performance of the industrial
work solenoid, reducing its size or a combination of these
factors. While controls are an added cost item, they can
often offset other costs by reducing the size and cost of
the industrial work solenoid required for the task and/or by
simplifying the entire mechanism of which the industrial
work solenoid is a component.
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Industrial Work Solenoid Application
Guidelines
The
following information should be determined to correctly
choose an industrial
work solenoid. If you are unsure of some of your application
parameters, Trombetta's engineers will assist you in
defining your parameters.
- 1.
What is the linear movement needed?
- When
designing systems with levers and linkages, engineers are
often confronted with the need to make a decision about
performing work through high forces and short strokes
versus
lower
forces and longer strokes. Once you have basic limits in
mind, Trombetta can offer assistance in making the choice
that will yield the most optimum overall design
results.
- 2.
How much force is required to perform the
operation?
- The
industrial
work
solenoid
should be sized so the force exerted at 85% of indicated
line voltage will perform the operation.
- 3.
What is the space limitation for the
industrial
work
solenoid?
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- 4.
What is the duty cycle of the industrial work
solenoid?
- Continuous:
Industrial
work solenoid coil is electrically energized without
interruption for 30 minutes or more.
- Intermittent:
Industrial
work solenoid
coil is electrically energized for 3 minutes or less and
the time between energizing and de-energizing is
sufficient to allow cooling of the
industrial
work
solenoid.
- Pulse:
Industrial
work solenoid coil is energized long enough to seat
plunger and de-energized long enough to cool
sufficiently.
- Rapid:
Industrial
work solenoid coil is energized and insufficient time is
allowed for cooling.
- 5.
What is the operating temperature range?
- Standard
coils are designed for a temperature rise of 85 degrees C
maximum plus the ambient temperature.
- Standard
Various insulation materials are
available:
Class A-
105
degrees
C
Class B-
130
degrees
C
Class F-
155
degrees
C
Class H-
180
degrees
C
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- 6.
Are there any special industrial environmental
concerns?
- Humidity
and water splash
- Oil
spray or immersion
- Sand,
dust or dirt
- Thermal
shock
- Physical
shock
- Vibration
- Radiation
- 7.
Is there need for additional circuit
protection?
- If
you are uncertain, consult with our Sales Representatives
once your application specifications are developed and an
industrial work solenoid selection is made.
- 8.
What size lead wire and length of lead is
required?
- Wiring
requirements vary widely by application and industrial
work solenoid type. The table below is provided as an
example which is applicable to the majority of
Trombetta's engine related industrial work solenoids. If
you are uncertain about your wiring needs, please consult
with our staff.
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