Patent Application
20150139817
1. Field of the Invention
The present invention is in the field of vacuum systems comprising a blower and a vacuum pump.
2. Description of Related Art
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
As further shown in
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
Other aspects, objects, and advantages of the present invention can be obtained from a study of the drawings, the disclosures, and the appended claims.
| Number | Date | Country | |
|---|---|---|---|
| 61906205 | Nov 2013 | US |
