Electricity: motive power systems – Switched reluctance motor commutation control
Reexamination Certificate
2000-08-21
2001-08-14
Ip, Paul (Department: 2837)
Electricity: motive power systems
Switched reluctance motor commutation control
C318S245000, C318S434000, C318S599000
Reexamination Certificate
active
06274991
ABSTRACT:
BACKGROUND OF THE INVENTION:
Field of the Invention
The invention relates to a method for detecting the rotational speed of electronically commutated fans, in which the rotational speed is indicated by a clock signal having a corresponding number of clock pulses per unit time. The invention also relates to a circuit configuration for detecting the rotational speed of electronically commutated fans, including a device for producing a clock signal with a corresponding number of clock pulses per unit time corresponding to the rotational speed of the fan.
Relatively powerful power supply units need electronically commutated fans to cool them. Electronically commutated fans cause current fluctuations on their power supply lines, which vary from fan to fan and not only from fan type to fan type.
In order to monitor and to control the fans, the rotational speed of the fans has to be detected electronically to derive a clock signal therefrom having an appropriate or corresponding number of clock pulses per unit time.
It is known for special fans to be used which pass an internal clock signal to the exterior from the electronic commutation through an additional line as a clock signal as mentioned above (see Papst Catalog, Equipment Fans, 94/95, Papst-Motoren GmbH & Co KG, Karl-Maier-Stra&bgr;e 1, D-78112 St. Georgen/Schwarzwald, P.O. Box 1435, in the Chapter entitled “Equipment fans for DC voltage” and “Variants”). The disadvantage thereof is that such special fans are expensive.
It is also known for the current fluctuations which are caused by a fan to be detected by a current measurement resistor, to be filtered out through a high-pass filter, and then to be supplied to a pulse former in order to form the clock pulses of the clock signal mentioned above (German Published, Non-Prosecuted patent application 26 17 131, corresponding to U.S. Pat. No. 4,097,789). The disadvantage thereof is that the level and the form of the current fluctuations which are caused by the fan on its power supply lines differ to such an extent from fan to fan that matching to each fan is required.
Furthermore, German Published, Non-Prosecuted Patent Application DE 196 01 040 A1 discloses a method and a circuit configuration for detecting the rotational speed of electronically commutated fans, in which the rotational speed is indicated by a clock signal with an appropriate number of clock pulses per unit time, and a DE Company Document: “Motor Control Seminar 1986”, page E15, SGS Halbeiter Bauelemente GmbH, April 1986, discloses the use of maximum current gradients for measuring current fluctuations which are caused by fans on the power supply lines as a function of the rotational speed, and deriving clock signals for rotational speed information therefrom.
SUMMARY OF THE INVENTION:
It is accordingly an object of the invention to provide a method and a circuit configuration for detecting the rotational speed of electronically commutated fans, which overcome the hereinafore-mentioned disadvantages of the heretofore-known devices and methods of this general type and with which the rotational speed of electronically commutated fans can be detected at low cost and in a simple way.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method for detecting the rotational speed of electronically commutated fans, which comprises indicating a rotational speed of an electronically commutated fan with a clock signal having a corresponding number of clock pulses per unit time; forming the clock pulses of the clock signal with a pulse former having a comparator serving as an input stage; measuring maximum current gradients of current fluctuations caused by the fan on power supply lines of the fan as a function of the rotational speed; and automatically adapting an amplification range and switching threshold of the comparator in dependence on a result of the measurement.
With the objects of the invention in view, there is also provided a circuit configuration for detecting the rotational speed of electronically commutated fans, comprising a device for producing a clock signal with a corresponding number of clock pulses per unit time corresponding to a rotational speed of an electronically commutated fan having power supply lines; a pulse former forming the clock pulses of the clock signal; a comparator serving as an input stage for the pulse former; a device for detecting maximum current gradients of current fluctuations caused by the fan on the power supply lines; and a device for automatically adapting an amplification range and switching threshold of the comparator.
The method and the circuit configuration make expensive special fans superfluous, so that the rotational speed can be detected at low cost. Furthermore, the respective matching measures to any fan which is used are superfluous, so that the rotational speed can likewise be detected in a simple way. So-called normal fans of all types may be used. The adaptation to a respective fan is carried out automatically.
Empirical measurements on a large number of different fans and fan types have shown that the current fluctuations which are caused by them on their power supply lines generally occur with considerably more severe negative current gradients than positive gradients. More accurate results thus allow rotational speed detection based on the negative current gradients of the current fluctuations. However, in the relatively small number of fans and fan types in which the positive current gradients are more severely pronounced than the negative current gradients, the negative current gradients are still sufficiently strongly pronounced that reliable and accurate detection of the rotational speed of the fans can always be ensured.
Thus, in accordance with another mode of the invention, the negative current gradients of the current fluctuations which are caused by a fan on its power supply lines are used to evaluate the rotational speed.
In accordance with a further mode of the invention, not only the amplification range and the switching threshold of a comparator, but also the determined maximum negative current gradients are matched in an appropriate ratio, which results in the provision for rotational speed detection immediately assuming a steady state once again.
In accordance with an added mode of the invention, the automatic adaptation is carried out in discrete steps. The implementation complexity is thus less than for continuous matching.
The above-mentioned considerations in this case apply not only to the method but also to the circuit configuration.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a method and a circuit configuration for detecting the rotational speed of electronically commutated fans, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.
REFERENCES:
patent: 4475070 (1984-10-01), Wilkerson
patent: 4527101 (1985-07-01), Zavis et al.
patent: 4823060 (1989-04-01), Doemen
patent: 4924420 (1990-05-01), Hadley et al.
patent: 4928045 (1990-05-01), Doemen
patent: 4955431 (1990-09-01), Saur et al.
patent: 5153492 (1992-10-01), Landseadel
patent: 5448143 (1995-09-01), Pecone
patent: 5654654 (1997-08-01), Franklin
patent: 5717302 (1998-02-01), Sakai et al.
patent: 5718373 (1998-02-01), Kim et al.
patent: 5731671 (1998-03-01), Adam et al.
patent: 5862301 (1999-01-01), Gontowski
patent: 5889469 (1999-03-01), Mykytiuk et al.
patent: 6008603 (1999-12-01), Jones et al.
patent: 6023139 (2000-02-01), Chin
patent: 26 17 131 A1 (
Greenberg Laurence A.
Ip Paul
Lerner Herbert L.
PCS PC-Systeme Entwicklungs-und Produktionsgesellschaft mbH & Co
Stemer Werner H.
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