U.S. patent application number 14/463579 was filed with the patent office on 2015-05-21 for ramp-up optimizing vacuum system.
The applicant listed for this patent is GARDNER DENVER THOMAS, INC.. Invention is credited to Joseph L. KOWALSKI.
Application Number | 20150139817 14/463579 |
Document ID | / |
Family ID | 52673557 |
Filed Date | 2015-05-21 |
United States Patent
Application |
20150139817 |
Kind Code |
A1 |
KOWALSKI; Joseph L. |
May 21, 2015 |
RAMP-UP OPTIMIZING VACUUM SYSTEM
Abstract
A ramp-up optimizing vacuum pump system comprising a vacuum pump
in fluid communication with a blower and one or more apparatus and
operable to create a vacuum flow from the one or more apparatus
through the outflow of the vacuum pump. The blower is positioned
between the vacuum pump and one or more apparatus. The blower
includes a blower motor which is controlled by a blower controller
and a unit controller. The unit controller increases the blower
speed at a predetermined ramp-up rate. The blower controller
optimizes the ramp-up rate of the blower based on the operating
conditions by monitoring the current draw of the motor and the
blower speed. If at any time the current draw exceeds a
predetermined maximum at a certain blower speed, the blower
controller maintains the blower speed until the current draw
decreases below the maximum and then continues ramp-up up at the
predetermined ramp-up rate.
Inventors: |
KOWALSKI; Joseph L.; (Fox
River Grove, IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GARDNER DENVER THOMAS, INC. |
Sheboygan |
WI |
US |
|
|
Family ID: |
52673557 |
Appl. No.: |
14/463579 |
Filed: |
August 19, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61906205 |
Nov 19, 2013 |
|
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Current U.S.
Class: |
417/44.11 |
Current CPC
Class: |
F04B 37/14 20130101;
F04B 45/04 20130101; F04C 23/006 20130101; F04C 28/06 20130101;
F04B 25/00 20130101; F04B 49/02 20130101; F04C 25/02 20130101 |
Class at
Publication: |
417/44.11 |
International
Class: |
F04B 25/00 20060101
F04B025/00; F04C 28/06 20060101 F04C028/06; F04C 23/00 20060101
F04C023/00; F04C 25/02 20060101 F04C025/02; F04B 37/14 20060101
F04B037/14; F04B 49/02 20060101 F04B049/02 |
Claims
1. A ramp-up optimizing vacuum system comprising: a blower having a
gas inlet and a gas outlet, a vacuum pump with a gas inlet and a as
outlet, a gas line connecting said blower outlet to said vacuum
pump inlet; a blower motor connected to said blower to rotate a
rotor of said blower; a first sensor; a second sensor; a motor
controller connected with said blower motor, said first sensor and
said second sensor; and said motor controller operable to ramp-up
said blower from a blower speed of from zero to an operating blower
speed at a predetermined ramp-up rate at start-up; wherein during a
ramp-up of said blower from the blower speed of zero to the
predetermined operating blower speed, said motor controller at a
plurality of predetermined intervals, based on information from the
first sensor, determines a measured blower speed measured blower
speed, and based on information from the second sensor determines a
measured current draw, and compares the measured current draw to a
predetermined maximum current draw value which corresponds to the
measured blower speed, and wherein the motor controller allows
either (1) the continued ramp-up of said blower speed to said
operating blower speed at said predetermined ramp-up rate if said
measured current draw is less than said maximum current draw value
for the measured blower speed, or (2) if said measured current draw
exceeds said maximum current draw value for said measured blower
speed, said motor controller stops said ramp-up without a signal
being sent to operate said blower at a blower speed less than said
measured speed, said blower allowed to operate at said measured
speed.
2. The ramp-up optimizing system of claim 1 wherein the
predetermined maximum current draw value which corresponds to the
measured blower speed is from a plot of predetermined maximum
current draw values against blower speeds.
3. The ramp-up optimizing system of claim 1 wherein each interval
of said plurality is a verification/comparison interval.
4. The ramp-up optimizing vacuum system of claim 1, wherein said
vacuum pump is a diaphragm pump.
5. The ramp-up optimizing vacuum system of claim 1, wherein said
blower is a roots type blower.
6. The ramp-up optimizing vacuum system of claim 1, wherein the
pre-determined ramp-up rate is the fastest ramp-up rate of the
vacuum system theoretically possible.
7. The ramp-up optimizing vacuum system of claim 1 wherein there
are thirty intervals per revolution of a motor shaft of said blower
motor.
8. The ramp-up optimizing vacuum system of claim 1 wherein pressure
sensors are not used to control said ramp-up of said blower to said
operating speed.
9. The ramp-up optimizing vacuum system of claim 1 wherein the
connection between the motor controller and first sensor is
wireless and the connection between the motor controller and the
second sensor is wireless.
10. The ramp-up optimizing vacuum system of claim 1 wherein the
blower speed is measured in one of revolutions per unit of time of
a shaft of the blower motor or a rotor shaft or a rotor.
11. A method for optimizing a ramp up of a speed of a blower speed
of a blower in a vacuum system from zero to an operating blower
speed, the method comprising: supplying current to a blower motor
to ramp-up of the speed of the blower to the operating blower speed
at a predetermined ramp-up rate; at a first predetermined interval
front a plurality of predetermined intervals, determining a
measured current draw of the blower motor and determining a
measured blower speed of the blower, and comparing said measured
current draw with a predetermined maximum current draw value for
said measured blower speed; continuing the ramp-up of said blower
speed to said operating blower speed at said predetermined ramp-up
rate if said measured current draw is less than said predetermined
maximum current draw value for the measured blower speed, or if
said measured current draw exceeds said predetermined maximum
current draw value for said measured blower speed, stopping said
ramp-up without as signal being sent to operate said blower at a
blower speed less than said measured speed and allowing said blower
to operate at said measured speed.
12. The method for optimizing the ramp up of a speed of a blower
speed of a blower in a vacuum system from zero to an operating
blower speed of claim 11 comprising the further steps of: allowing
a density of gas passing through said blower to decrease after said
measured current draw is greater than the predetermined maximum
current draw value for the measured speed; after said decrease in
said gas density, determining another measured current draw of the
blower motor and determining another measured blower speed at
another predetermined interval from said plurality of predetermined
intervals; supplying an amount of current to the blower motor to
increase the another measured current draw in magnitude to equal a
predetermined maximum current draw for the another measured
speed.
13. The ramp-up optimizing vacuum system of claim 1 wherein the
first sensor and/or the second sensor are connected wirelessly to
the motor controller.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention is in the field of vacuum systems
comprising a blower and a vacuum pump.
[0003] 2. Description of Related Art
[0004] Previous vacuum systems control and monitor the ramp-up in
speed of a blower upstream of a vacuum pump from zero to a desired
operating speed by using control systems that include pressure
sensors positioned at the outflow of the blower and upstream of the
vacuum pump to which the outflow of the blower is fluidly
connected. Namely, pressure sensors were placed to monitor the
pressure in the flow channel connecting the blower outflow to the
vacuum pump inlet. These pressure sensor based control systems
adjust the speed of the blower motor based upon the pressure
reading. A control system using pressure sensors to govern ramp-up
does not monitor the current draw of the motor. The ramp-up
procedures for a vacuum system utilizing pressure sensors to
monitor and control the operation of the vacuum system are
conservative so that the blower motor never operates at a speed
which approaches or exceeds the maximum current draw.
[0005] Generally, prior vacuum systems use ramp-up protocol that
gradually increases the speed in incremental steps to ensure that
the blower motor does not exceed the maximum current draw at each
point in the ramp-up operation. This conservative approach ensures
no overage in current draw occurs to prevent damage to the blower
motor and/or other system components. However, this ramp-up
approach prolongs the time it takes for the vacuum system to
ramp-up from a stand-still to the desired operating speed.
SUMMARY OF THE INVENTION
[0006] The present vacuum system does not utilize pressure sensors
to control the ramping up of blower speed from zero to an operating
speed. The system rather monitors the actual current draw of the
blower motor in order to optimize the ramp-up speed of the blower
of the vacuum system. The present configuration allows the vacuum
system to mach the operating speed as soon as physically possible
while protecting the components of the vacuum system from
overheating due to excessive current draw. The present application
is directed toward a ramp-up optimizing vacuum system comprising a
blower having an intake port and an exhaust port. The blower may be
in fluid communication with one or more apparatus and operable to
create a vacuum fluid flow from the one or more apparatus. The
system also includes, downstream of the blower, a vacuum pump
having an inlet and an outlet. Fluid drawn from the apparatus by
the blower is discharged at the blower outlet and from the outlet
enters the vacuum pump at the vacuum pump inlet. The fluid is
exhausted from the vacuum pump from the vacuum pump outlet. The
blower is positioned in a vacuum circuit between the vacuum pump
and the one or more apparatus. The blower, relative to the fluid
flow, is downstream of the apparatus and upstream of the vacuum
pump. The blower is coupled to a blower motor for rotating the
blower's fluid driving member, such as rotor(s) and more
particularly its lobes, in the case of a roots blower, at a blower
speed.
[0007] The vacuum system also includes a first sensor for obtaining
information during operation of the blower. The motor controller
processes the information obtained by the first sensor to determine
a measured blower speed. The measured blower speed is an actual
blower speed. The system also includes a second sensor for
obtaining information during operation of the blower. The motor
controller processes the information obtained by the second sensor
to determine a measured current draw. The measured current draw is
an actual current draw value. The controller compares the measured
current draw value against a predetermined maximum current draw
value for the measured speed.
[0008] The motor controller is in electronic communication with the
blower motor, the first sensor, and the second sensor. The motor
controller is operable to effectuate an increase in the blower
speed between zero and an operating blower speed which could be a
maximum rated blower speed. The present vacuum system also includes
a unit controller that is in electronic communication with the
motor controller, and a power source. The unit controller can
provide an electric signal to the motor controller. Based on the
signal the motor controller sends current to the blower to ramp-up
the blower speed to the operating blower speed at a predetermined
ramp-up rate during operation or the pump. The predetermined
ramp-up rate, change in speed per unit of time, may be the quickest
ramp-up rate that is theoretically physically possible for the type
and size of the particular components of the present vacuum
system.
[0009] During the ramp-up of the blower speed from zero to the
operating blower speed, information from the first sensor is
supplied to the motor controller. Information from the second
sensor is supplied to the motor controller. At predetermined
intervals, the motor controller processes the information front the
first sensor to determine a measured blower speed. The motor
controller also processes the information from the second sensor to
determine a measured current draw. The controller then compares the
measured current draw with a predetermined maximum current draw
value for the measured blower speed. The motor controller then
either continues to increase the blower speed at the predetermined
ramp-up rate if the measured current draw is less than the maximum
current draw value for the corresponding measured blower speed, or
if the measured current draw exceeds the maximum current draw value
for the measured blower speed, the motor controller stops the
ramp-up in speed without a signal being sent from said vacuum
system to operate the blower at a blower speed less than said
measured speed; the blower is allowed to operate at the measured
speed. The motor controller of the present vacuum system can
interrupt or over-ride the ramp-up signal provided by the unit
controller to stop the ramp-up if the measured current draw exceeds
the predetermined maximum current draw value for the measured
blower speed.
[0010] The system allows the actual current draw to all due to a
change (lessoning of the density of the fluid) in the blower as the
vacuum in the apparatus increases. Once the actual current draw
falls to below the predetermined maximum current draw value for the
measured speed, the motor controller allows the blower to continue
the ramp-up in speed at the predetermined rate. Once the blower has
reached the desired blower speed for the desired operating
conditions, the first sensor and second sensor may be used to
monitor and adjust the operation of the present vacuum system
during its operation.
[0011] Other aspects and advantages of the present invention will
be apparent from the following detailed description of the
preferred embodiments and the accompanying drawing figures.
BRIEF DESCRIPTION OF THE DRAWING
[0012] The accompanying drawings form a part of the specification
and are to be read in conjunction therewith, in which like
reference numerals are employed to indicate like or similar parts
in the various views.
[0013] FIG. 1 is a schematic view of one embodiment of a ramp-up
optimizing vacuum system in accordance with the teachings of the
present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0014] The following detailed description of the present invention
references the accompanying drawing figures that illustrate
specific embodiments in which the invention can be practiced. The
embodiments are intended to describe aspects of the present
invention in sufficient detail to enable those skilled in the art,
to practice the invention. Other embodiments can be utilized and
changes can be made without departing from the spirit and scope of
the present invention. The present invention is defined by the
appended claims and, therefore, the description is not to be taken
in a limiting sense and shall not limit the scope of equivalents to
which such claims are entitled.
[0015] FIG. 1 illustrates a schematic view of the present ramp-up
optimizing blower-vacuum system 10. The system comprises a vacuum
pump 12 and a blower 14. The system creates a vacuum at one or more
apparatus 16 that is in fluid communication with both vacuum pump
12 and blower 14. The system optimizes the time it takes to ramp-up
the blower from zero to a desired operating blower speed. In
connection with optimizing the time, the system provides for a
ramp-up in speed to the operating speed which may be the maximum
rated operating blower speed. The blower speed is measured as the
revolutions per minute of the shaft of the blower motor 18. It is
the motor shaft that drives the shall of the blower's fluid driving
member, such as in the case of a roots-type blower, the shaft of
the rotors and more particularly lobes The blower speed could be
measured in other ways such as measuring the speed of the rotor
shaft or rotors in revolutions per minute. Other time units could
be used. Blower 14 of vacuum system 10 is coupled to a blower motor
18 for rotating blower 14's fluid driving member. Vacuum system 10
further includes a control system 9 comprising a motor controller
20 in electronic communication with blower motor 18 and as unit
controller 22 in electronic communication with the motor controller
20. Vacuum pump 12 may be any of a variety of pumps. Pump 12 in the
present embodiment is a diaphragm pump. Vacuum system 10 may be
utilized to provide a vacuum at a number of apparatuses 16 being
deployed in a vacuum network.
[0016] Blower 14 may be any of a variety of blowers. In the present
embodiment, blower 14 is a roots type blower. Blower 14 is driven
by blower motor 18 at a desired operating blower speed. Blower
motor 18 can be an of a variety of motors. In the present
embodiment blower motor 18 is a brushless DC ("BLDC") motor. In the
present example, the first sensor 26 is a hall sensor. A hall
sensor is used to sense, detect, when the blower motor is ready for
a commutation. The sensor detects when the blower is ready for a
commutation by detecting a magnetic field. When the field is
detected the hall sensor sends a signal to the motor controller.
The motor controller 20 based On the signal controls the motor 18
to perform a commutation. A commutation is when the current and
polarity is changed in the blower motor. Commutations are used to
cause the rotor of the blower motor to rotate. In the present BLDC
motor 30 commutations are performed per revolution of the motor
shaft. A circuit can be used as an alternative to the hall sensor
to detect when the motor is ready for a commutation. The circuit
detects a current peak to determine when the motor is ready for a
commutation. The circuit, when the peak is detected, sends a signal
to the motor controller. The motor controller, based on the signals
from the hall sensor or circuit can determine the speed of the
blower. For instance if the controller receives 60 commutation
signals in a second, it can determine that there are 600
commutations in a minute and that the motor shaft is running at a
speed of 120 revolutions per minute. The sensor could be an optical
sensor reading the movement of the motor shaft. In general the term
first sensor 26 as used herein encompasses any sensor or detector,
which based, at least partially on information from the sensor, the
motor controller determines the measured blower speed, the actual
blower speed. The above described circuit and hall sensor are thus
first sensors. A speed sensor, such as the above described optical
sensor, is thus a first sensor 26.
[0017] As further shown in FIG. 1, vacuum system 10 includes a
second sensor 24 for providing information to measure the current
draw of blower motor 18 during operation of the pump. In general
the term second sensor 24 as used herein encompasses any sensor or
detector, which based, at least partially on information from the
sensor, the motor controller determines the measured current draw,
the actual current draw value. A current sensor is thus a second
sensor. Second sensor 24 and first sensor 26 are in communication
with the blower motor 18 and motor controller 20. Sensor 24, sensor
26, motor controller 20, and unit controller 22 are used in
combination to optimize the time to ramp-up the blower speed from
zero to an operating blower speed, which may be the maximum rated
blower speed. The operating blower speed is a desired operating
speed. It is a predetermined operating speed. Sensor 24, sensor 26,
motor controller 20, and unit controller 22 may also be used in
combination to monitor and control the operation of vacuum system
10 during operation of vacuum system 10 after the operating blower
speed has been reached.
[0018] Vacuum system 10 further comprises a first vacuum line 28
which places apparatus 16 in fluid connection with the inflow 30 of
blower 14. The vacuum line is a gas line. The term gas as used
herein is broad enough to include ambient air, mixtures of ambient
air and other gasses, and mixtures of compressible and
incompressible fluid such as for example air and water. Vacuum
system 10 may include additional apparatuses (not shown) having a
gas connection to line 28. Moreover, for purposes of this
application, apparatus 16 may be considered and defined as any
termination point, device, or outlet at which a person of skill in
the art desires to effectuate a vacuum pressure (negative
pressure). Vacuum system 10 also comprises a second vacuum line 12
placing outflow 34 of blower 14 in fluid connection with an intake
port 36 of vacuum pump 12. The line 32 is a gas line. Vacuum pump
12 also has an exhaust port 38 wherein the gas is exhausted from
vacuum system 10. Upon operation of blower 14 and vacuum pump 12, a
vacuum is created in apparatus 16. Gas flows from the apparatus 16
to blower 14 and from the blower 14 to the vacuum pump 12. The gas
is exhausted from pump 12 at outlet 38. The flow of gas creates the
vacuum (negative pressure) in the apparatus. FIG. 1 further
illustrates the direction of gas flow being shown by flow direction
arrow 40a in first vacuum line 28 and flow direction arrow 40b in
second line 34. The configuration of vacuum system 10 does not
require or include pressure sensors to monitor the pressure in
vacuum line 32. Thus there are no pressure sensors in fluid
connection with line 32. Also, the configuration of vacuum system
10 does not require or include pressure sensors to monitor the
pressure in vacuum line 28. Thus there are no pressure sensors in
fluid connection with line 28. The system controls and monitors the
ramp-up of the blower speed to the predetermined operating speed
without reliance on pressure sensors, such as without the use of
signals from pressure sensors.
[0019] Unit controller 22 may be any of a variety of control
devices known in the art. Unit controller 22 may include an on/off
switch to shut-off the supply of electricity to motor controller
20. As part of the on/off protocol of unit controller 22, the
on/off function selectively allows electrical current to flow to
motor controller 20 and subsequently to blower motor 18. The unit
controller delivers a signal to the motor controller 20 to ramp-up
the blower speed at a predetermined ramp-up rate from zero to an
operating blower speed. The predetermined, rate may be
pre-programmed or hard wired into motor controller 20 and/or unit
controller 22. The predetermined ramp-up rate includes ramping up
the blower speed from zero to the operating or maximum blower speed
as quickly as theoretically possible for the type and size of
components of vacuum system 10 and more particularly blower 14 and
motor 18. Alternatively, the predetermined ramp-up rate may be
another user defined rate.
[0020] Motor controller 20 may be any of a variety of control
devices known in the art. Motor controller 20 receives electrical
current from unit controller 22. Based on the signal received from
the controller 22, the controller 20 sends current to the blower
motor 18 to effectuate the ramping-up of the blower speed. Motor
controller 20 is in electronic communication with sensor 24 and
sensor 26 wherein motor controller 20 is operable to receive
signals carrying information from the sensors 24 and 26 to
determine the actual current draw value (measured current draw) and
actual blower speed (measured blower speed) respectively. Motor
controller 20 is operable to regulate the current received by the
motor to maintain the measured speed and delay the ramp-up to the
desired speed depending upon the measured current draw and the
measured blower speed. Motor controller 20 and unit controller 22
generally comprise a memory and a processor for receiving and/or
storing the measured values from sensors 24 and 26 and performing
the algorithm's necessary to determine the current to be sent to
the blower motor 18. Such controller configurations are generally
known in the art.
[0021] In use, vacuum system 10 may be utilized in various
industrial, educational, and research applications. For example, an
embodiment of vacuum system 10 may be utilized in schlenk lines
and/or within vacuum networks. One particular advantage of the
present vacuum system 10 is the efficiency gained. It is well
recognized in the art that blower 14 cannot start immediately at
full speed as it would over-heat the controllers 22, 22 and motor
18. The regulated ramp-up in blower speed provided by the
controllers 20, 22 to the desired operating speed prevents
over-heating of the blower motor and related damage to the
components.
[0022] When starting, vacuum system 10 from a stand-still, unit
controller 22 provides a signal to motor control unit 20 to provide
a current to motor 18 to increase the blower speed of the blower 14
at a predetermined ramp-up rate. The motor controller 20 regulates
the current to affect the ramp-up. The ramp-up rate may be the
quickest ramp-up rate physically possible considering the type and
size of the vacuum system components. Such theoretical ramp-up may
be determined by a person of skill in the art using known
mathematical formulae. Blower motor 18 draws the current from the
power source through the motor controller 20 as necessary to
effectuate the theoretical ramp-up rate.
[0023] During operation of blower 14 and vacuum pump 12 during
ramp-up, if the outflow of blower 14 is greater than the outflow of
vacuum pump 12, then a positive pressure builds up in second vacuum
line 32. This positive pressure increases the load on blower motor
18 and requires additional current to maintain the blower speed.
If, however, the outflow of blower 14 is less than the outflow of
vacuum pump 12, then a vacuum pressure is present in second vacuum
line 32. Thus, one of the purposes of the combination of motor
controller 20 and unit controller 22 is to control blower motor 18
such that the outflow of blower 14 equals the outflow of vacuum
pump 12 throughout the ramp-up process.
[0024] Previous ramp-up control systems utilized pressure sensors
at the outflow of the blower to control the speed of the blower
motor. Namely, pressure sensors were placed in fluid connection in
the fluid hue connecting the blower and the vacuum pump. The
ramp-up protocol in prior vacuum systems that utilize pressure
sensors to monitor and control the blower speed during ramp-up are
conservative to prevent current overload. The present vacuum system
10 does not utilize any pressure sensors in order to control or
optimize the amount of time it takes to ramp-up the blower speed
from zero to the operating speed. For instance it does not rely on
any signals from pressure sensors to ramp-up the blower speed to
the operating speed. To optimize the time it takes to ramp-up, the
vacuum system allows for the operating blower speed to be achieved
as quick a possible without a prolonged drawing of current which is
above a predetermined maximum current draw value at its measured
speed. The use of sensor 24 and sensor 26 with controller 20 and 22
allows vacuum system 10 to reach the desired operating conditions
as quickly as physically possible while preventing damage to vacuum
system 10 due to current overload.
[0025] The actual current draw is an indicator of the blower load
experienced by blower motor 18 during operation. The blower load
may be a function of the speed of the blower, the pressure of the
gas going through the blower, the density of the gas going through
the blower, and/or other factors recognized by a person of skill in
the art. If the actual current draw value exceeds the predetermined
maximum current draw value far significant periods of time blower
motor 18, controller 20 and controller 22 may overheat resulting in
damage and/or shutdown. Thus, the present vacuum system 10 operates
to keep the actual current draw value as close as possible to the
predetermined maximum current draw value for a measured blower
speed during ramping-up to the operating blower speed and to
minimize the time period required for the blower 14 to ramp-up from
a blower speed of zero to the operating blower speed while
protecting the components from overheating and related damage due
to current overload. To ensure that blower motor 18 does not draw
too much current while blower 14 is ramping up to an operating
blower speed which may be the maximum rated blower speed, vacuum
system 10 includes motor controller 20 which monitors both the
actual current draw of motor 18 and the blower speed of blower 14.
Vacuum system 10 optimizes the ramp-up of blower 14 using a plot of
predetermined maximum current draw values against corresponding
blower speeds as the blower speed increases from zero to the
operating blower speed which may be the maximum rated blower speed.
During each interval of regular predetermined intervals, a
predetermined maximum current draw value for a measured speed is
compared against a measured current draw value for the measured
speed. The measured current draw value is based, at least partially
on information from the second sensor 24 and is received from the
second sensor by the motor controller and can be carried by signals
and the signals can be from said sensor 24. The measured speed is
based, at least partially on information from the first sensor 26
and can be received from the first sensor by the motor controller
and can be carried by signals and the signals can be from the first
sensor 26. At each verification/comparison interval during ramp-up,
motor controller 20 either allows the ramping-up of the blower
speed at the predetermined rate, change in speed per unit of time,
to continue or instructs the blower motor 18 to stop the ramp-up in
speed. The motor controller 20 does not decrease the speed of the
motor 18.
[0026] During the ramp-up of the blower speed, if the magnitude of
the actual current draw exceeds the maximum current draw value for
the measured blower speed at a verification/comparison interval,
than motor controller 20 stops ramping up the speed of the blower.
The last measured speed is not decreased by the controller 20. The
motor controller does not decrease the speed of the blower. The
blower is allowed to operate at the measured blower speed. As the
blower 14 and vacuum pump 12 continue to draw gas from the
apparatus 16, the density of the gas passing through the blower 14
and vacuum pump 12 decreases. The lower density lowers the actual
current draw by the motor for the actual blower speed. The current
draw thus falls at the blower's current speed. Thus at the next
verification/comparison interval the measured current draw is less
than the maximum current draw value for the measured blower speed.
Because at each verification/comparison, if the measured current
draw value is less than the maximum current draw value for the
measured blower speed, the blower speed is allowed continue to be
ramped up at the predetermined ramp-up rate, the motor 18 and thus
the blower at this comparison is allowed to continue to be ramped
up and the ramp-up protocol continues. Accordingly, once the
measured current draw is less than the maximum current draw value
for the measured blower speed, motor control 20 continues to
ramp-up the blower speed at the predetermined ramp-up rate. It is
feasible that the ramp-up protocol will continue once the measured
current draw is at the maximum current draw value, as opposed to
below the maximum.
[0027] In one embodiment, vacuum system 10 performs the
verification/comparison for each commutation of the blower motor
18, There are 30 commutations per revolution of the blower motor 18
shaft. However, a person of skill in the art will appreciate that
the number of verifications/comparisons may be at any predetermined
interval which provides the person of skill in the art confidence
that vacuum system 10 is adequately protected from damage to blower
motor 18 when the current draw exceeds the maximum current draw.
The shorter the time period per verification/comparison, the closer
the ramp-up rate will match the predetermined fastest ramp-up rate
possible. Thus, components at the present vacuum system 10 provide
an optimized ramp-up time period so that vacuum system 10 can reach
desired operating conditions and performance as quickly as
physically possible while also preventing blower motor 18,
controller 20 and 22 from overheating.
[0028] Motor controller 20, sensor 24 and sensor 26 may also be
used to monitor and control the operation of vacuum system 10 when
it is operating at the desired operating conditions. For example,
during operation of vacuum system 10 after it has reached the
desired operating conditions, if motor controller 20 determines an
actual current draw value by blower motor 18 that exceeds the
maximum current draw value for the measured speed, motor controller
20 may reduce the blower speed to reduce the current draw to the
maximum current draw. In this case the controller 20 and 22 allow
for a decrease in motor speed. While there are many changes in
operating conditions which affect the operation and current draw,
common events which may require mitigation by control system 19 may
include pumping on an oversized apparatus volume, and a sudden gas
in-rush to the apparatus. Once the condition which caused the
increase in blower load dissipates or passes, the blower speed may
increase to the optimal blower speed automatically when the control
system sets the actual current draw at the maximum current
draw.
[0029] As is evident from the foregoing description, certain
aspects of the present invention are not limited to the particular
details of the examples illustrated herein. It is therefore
contemplated that other modifications and applications using other
similar or related features or techniques will occur to those
skilled in the art. It is accordingly intended that all such
modifications, variations, and other uses and applications which do
not depart from the spirit and scope of the present invention are
deemed to be covered by the present invention.
[0030] Other aspects, objects, and advantages of the present
invention can be obtained from a study of the drawings, the
disclosures, and the appended claims.
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