Patent number 8613600 is assigned to
The following quote was obtained by the news editors from the background information supplied by the inventors: "The present invention relates to a vacuum pump system including a vacuum pump with brushless, multi-phase, synchronous motor with a permanently magnetically excited rotor, a control unit for controlling the vacuum pump and including a drive microcontroller and a final stage, and a further microcontroller for monitoring a rotational speed of the motor.
"In the past years, brushless motors with a permanently magnetically excited rotor and a shaft having a high rotational speed, found wide application as drives for vacuum pumps. To these pumps belong, e.g., turbomolecular pumps disclosed in German Publication DE-0S 103 31 932. The danger with these pumps lies in the high energy that is stored in the rotor. If this energy is released as a result of pump malfunction, i.e., in the environment, it can cause big damages. Therefore, the housings of the vacuum pump are so formed that they can absorb a substantial amount of the releasable energy. Generally, the energy, which is stored in the rotor, depends on the rotational speed of the rotor. In order to limit the maximum stored energy, the rotational speed should be limited to a highest permissible value. This rotational speed limitation must be insured even when the control electronics of the motor itself malfunctions. The rotational speed limitation also should include protection against an excessive rotational speed.
"German Publication DE-0S 102 15 896 suggests to provide in the vacuum pump, in addition to a microcontroller that directly assumes the functions of the motor electronics, a second microcontroller which, in addition to its other functions, monitors the first microcontroller. The drawback of this solution consists in that a large number of components needs to be provided on and in the vacuum pump. The arrangement of highly integrated electronic components on the pump itself might not be possible in many cases, e.g., in an environment with an intensive radiation. In addition, both microcontrollers depend for their operation on only one sensor that senses the rotation of the rotor, which limits the protection against malfunction. Furthermore, the division of the electronics between the vacuum pump and control electronics can lead to the limitation of exchangeability of the electronics and the vacuum pump, i.e., the vacuum pump and the electronics cannot be arbitrarily combined because, e.g., the functional features (e.g., the based code) of the microcontrollers should be adapted to each other. This is not user-friendly and is associated with increased costs.
"Accordingly, an object of the present invention is a vacuum pump system in which arbitrary combination of a vacuum pump and control electronics is possible and a reliable overspeed protection is insured."
In addition to the background information obtained for this patent, VerticalNews journalists also obtained the inventors' summary information for this patent: "This and other objects of the present invention, which will become apparent hereinafter, are achieved by providing, in the vacuum pump, pump type recognition means, and by assigning to the second microcontroller the function of turning off the final stage when the rotational speed exceeds a predetermined threshold.
"The inventive vacuum system proceeds from a system that includes a control unit and a vacuum pump, with the control unit including a drive microcontroller that controls a final stage and, thus, sets in rotation a brushless, multi-phase, synchronous motor with a permanently magnetically excited rotor. The drive microcontroller turns off before the threshold rotational speed is reached. According to the present invention, the second microcontroller forms part of the control unit, and the vacuum pump is provided with vacuum pump type recognition means that is evaluated by the control unit. In this way, the pump operates with a maximum allowable rotational speed. A signal proportional to the rotational speed of the rotor is communicated to the second microcontroller. When the second controller recognizes that the rotor exceeded the maximum permissible speed, it turns off the final stage that controls the motor.
"The advantage of this solution consists in that only a small number of electrical and electronic components are contained in the vacuum pump itself, namely, essentially the motor and the pump type recognition means. In its simplest form, the pump type recognition means is an electrical resistor the resistance value of which varies from pump to pump. In this way, a vacuum pump can be used in an environment in which because of radiation, the electronic components are subjected to a high load. Because it is the control electronics that determines the pump type, an arbitrary combination of the vacuum pump and the control electronics is possible. Expensive repairs of the vacuum pump in case of damage of the control electronics are eliminated, the defective control electronics is replaced in its entirety. Thereby, the servicing costs are reduced. This combination ability permits to replace the entire control electronics with a new model, which was difficult in the state-of-the-art, vacuum pump system. Because the second microcontroller that monitors the rotational speed and turns off the final stage, is arranged in the control unit, a more reliable protection against the speed exceeding the maximum permissible speed is obtained.
"According to an advantageous embodiment of the present invention, the second controller evaluates the pump type recognition means, which is provided in the vacuum pump, and determines the highest possible rotational speed for the vacuum pump and communicate it to the drive controller, e.g., over a serial data interface. This increase the reliability as the determination of the correct rotational speed is decoupled from the actual drive chain. It is a very effective embodiment as no additional components are necessary.
"According to a further advantageous embodiment of the present invention, the drive controller determines the rotational speed of the motor from a motor model and the phase currents. This embodiment is based on the knowledge that a synchronous motor operates best at a rotational speed with which a magnetic field, which is generated by the current flow through the winding, rotates. Thereby, both the operation and the protection against an excessive speed are effected without use of sensors. Therefore, there is no need for sensors in the vacuum pump, which further reduces the number of components.
"According to another embodiment, the second microcontroller determines the rotational speed from a signal generated by measurement of voltages applied to the phases. Because the rotational speed is determined from two different measurements, a separate rotational speed signal is communicated to each microcontroller, which increases the reliability of speed monitoring. Altogether, a redundant monitoring can be so formed that it is carried out through two channels, i.e., for each part of the monitoring system, there exists a second path.
"According to a further development of the present invention, the measurement of the currents and voltages on phases at current and voltage measurement points, which serves for determination of the rotational speed, takes place inside the control unit. This increases the ability to arbitrary combined control units with the vacuum pumps are and insures that for operation of the vacuum pump, only the pump type recognition system and the motor needs to be provided in the vacuum pump. In addition, the number of electrical connections, which are necessary between the control unit and the vacuum pump, is reduced.
"According to a further development of the present invention, the conductor through which the second controller turns off the final stage, is also connected with a corresponding input of the drive controller. Thereby, the drive controller recognizes an operational condition, which is not acceptable to it, and can undertake several controlled repeated starts.
"A still further embodiment of the present invention is based on measurement of voltage in the phases. These voltages are converted by an analog-to-digital converter, which is located in a section of the drive microcontroller, to a digital signal which is evaluated by the second microcontroller. As a result, additional converter components are not necessary.
"The novel features of the present invention, which are considered as characteristic for the invention, are set forth in the appended claims. The invention itself, however, both as to its construction and its mode of operation, together with additional advantages and objects thereof, will be best understood from the following detailed description of preferred embodiment, when read with reference to the accompanying drawings."
URL and more information on this patent, see: Losch, Wolfgang; Mueller, Andre. Vacuum Pump System. U.S. Patent Number 8613600, filed
Keywords for this news article include: Microcontroller,
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