WO1987000770A1 - Systeme prioritaire sur les signaux de protection contre des survitesses dans un appareil centrifuge - Google Patents

Systeme prioritaire sur les signaux de protection contre des survitesses dans un appareil centrifuge Download PDF

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Publication number
WO1987000770A1
WO1987000770A1 PCT/US1986/001488 US8601488W WO8700770A1 WO 1987000770 A1 WO1987000770 A1 WO 1987000770A1 US 8601488 W US8601488 W US 8601488W WO 8700770 A1 WO8700770 A1 WO 8700770A1
Authority
WO
WIPO (PCT)
Prior art keywords
signal
motor
rotor
overspeed
centrifuge
Prior art date
Application number
PCT/US1986/001488
Other languages
English (en)
Inventor
Robert J. Ehret
Original Assignee
Beckman Instruments, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Beckman Instruments, Inc. filed Critical Beckman Instruments, Inc.
Publication of WO1987000770A1 publication Critical patent/WO1987000770A1/fr

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B04—CENTRIFUGAL APPARATUS OR MACHINES FOR CARRYING-OUT PHYSICAL OR CHEMICAL PROCESSES
    • B04B—CENTRIFUGES
    • B04B9/00—Drives specially designed for centrifuges; Arrangement or disposition of transmission gearing; Suspending or balancing rotary bowls
    • B04B9/10—Control of the drive; Speed regulating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B04—CENTRIFUGAL APPARATUS OR MACHINES FOR CARRYING-OUT PHYSICAL OR CHEMICAL PROCESSES
    • B04B—CENTRIFUGES
    • B04B13/00—Control arrangements specially designed for centrifuges; Programme control of centrifuges
    • B04B13/003—Rotor identification systems
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/08—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for dynamo-electric motors
    • H02H7/093—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for dynamo-electric motors against increase beyond, or decrease below, a predetermined level of rotational speed

Definitions

  • This invention relates to an overspeed protection and shutdown system for centrifuge apparatus and, more particularly, to an improved overspeed shutdown system for centrifuge apparatus which is driven by an A.C. induction motor to shut, down the drive signal to the induction motor in the event that the conventional overspeed protection and shutdown circuit fails.
  • Biological research centrifuge apparatus require a wide variety of rotors interchangeably to be inserted on the rotor-receiving motor shaft hub so that a multiplicity of experimentation may be achieved by use .of a single centrifuge machine.
  • Each interchangeable rotor is of a different size and weight and may otherwise cause rotor mishap at differing maximum speeds depending on the strength and weight of the interchangeable rotor attached to the induction motor hub. Therefore, each rotor requires a separate identification and rating in order to assure safe usage of the centrifuge as the different rotors are interchanged during experimentation. It has been determined that the laboratory technician using the centrifuge rotor cannot always be relied upon to place the proper rotor into operation and run that rotor at no more than its rated speed.
  • U.S. Patent 3,436,637 there is disclosed one manner of overspeed shutdown protection.
  • U.S. Patent 3,436,637 describes an overspeed protection system having a transducer which detects through a phototransistor an optical signal whose frequency was a function of rotor speed of the centrifuge rotor. The detected frequency was mixed with a standard reference frequency to provide a difference frequency. The difference frequency was passed through a low pass filter to an alarm circuit for disconnecting the drive power to the centrifuge motor.
  • Each rotor had a maximum s.psed rating encoded as an integral part of its base in the farm of an optically detectable disc defining a plurality of sectors corresponding to the speed rating.
  • R.P.M. revolutions per minute
  • 14 sectors were sufficient to compare rotor speed with a local oscillator frequency of 15.5 kilocycles.
  • 19,787 R.P.M. 47 sectors were required to achieve the same comparison frequency.
  • As the rotor spins up to the speed of the reference frequency its difference from that frequency is diminished to within the range of the low pass filter.
  • the low pass filer for example, might be set at 40 cycles per second (Hz) so that when the frequency of. the rotor signal came within 40 Hz of the reference frequency, the system would shut down.
  • the low pass filter would activate a gate trigger signal, turning on a silicon-controlled rectifier (SCR) and diverting the main power current through a pathway other than the drive control circuit, shutting down the drive motor.
  • SCR silicon-controlled rectifier
  • Induction- motors have been used in centrifuges because they are brushless and not as likely to wear as D.C. motors.
  • An induction motor has current flow in its stator winding creating a rotating magnetic field for driving the motor and centrifuge rotor.
  • the frequency of the current signal imparted to the stator defines the synchronous speed of the motor.
  • An induction motor produces a driving torque at a speed below the synchronous speed. If the rotor speed is greater than the stator frequency, braking torque is produced. In either event, the induction motor must have slip.
  • the slip frequency is def-ined as the difference between the stator frequency and the actual rotational speed of the motor. During ordinary motor operation, it is desirable to maintain a constant slip frequency regardless of motor speed.
  • the system may cause the centrifuge motor to coast to a stop, thereby avoiding rotor mishap due to rotor overspeed.
  • This invention relates to an improved overspeed shutdown system for centrifuge apparatus wherein the improved system responds to a rotor overspeed alarm condition regardless of current and power control of the drive motor.
  • Induction motors require a tach signal which differs in frequency from the motor drive frequency signal in order to develop torque and be driven by an inverter. If one were to override and remove the tach signal and disconnect that signal from the inverter input, one could achieve motor shutdown even though the current command fails to control current and power to the drive motor.
  • a preferred embodiment which accomplishes this tach signal override configuration is disclosed in this application.
  • this alarm condition is signalled to a flip-flop or latch which responds to the alarm condition signal by changing state at its output from, for example, a normally logic "high” condition to a logic “low” condition.
  • This output signal is imparted, in the preferred embodiment, to one input of a logic gate, which preferably is a NOR or NAND logic gate. Also input to this logic gate is the tach signal from the drive motor. The tach signal is necessary for normal motor operation and is not usually interrupted by the logic gate. The improved alarm system places the tach signal at a second input to the logic gate.
  • the tach signal When the signal from the latch indicates alarm, the tach signal is inhibited and the inverter-motor controller no longer receives the tach signal necessary to drive the motor. In this manner, the induction drive motor may be shut down, regardless of the alarm system's ability to control current and power to the motor.
  • the drawing is a sole figure including a schematic diagram, partly in block form, of an improved overspeed shutdown system for a centrifuge apparatus constructed in accordance with the teachings of the present invention.
  • an overspeed shutdown system generally, having a number of elements in common with the overspeed shutdown system of prior U.S. Patent Nos. 3,436,637 and 4,284,931.
  • the circuitry of the invention is generally designed for use with centrifuge apparatus including a rotor 11 mounted for rotation on the drive shaft 12.
  • a full description of the alarm circuitry is provided by U. S. Patent 4,284,931, heretofore incorporated by reference.
  • a reflective disc 15 may be mounted on the underside of the rotor 11 which has alternating reflective and non-reflective sectors for the determination of the maximum safe rotor speed that a particular rotor is rated to operate at.
  • the tranducer means 13 detects a modulated light beam pattern eminating from the disc 15 when light, produced by the optical means 16, is reflected off the disc 15.
  • the transducer produces an alternating periodic real-time rotor signal corresponding in frequency to the modulated 'light beam. This rotor signal is transmitted along conductive pathway 14 for amplification by the amplifier 17.
  • the rotor signal is routed to frequency comparison circuitry comprising an exclusive OR gate 19 and a digital phase detector 35.
  • the rotor signal is compared to a synthesized reference signal generate by the oscillator 21, said oscillator 21 controlled by the crystal 22 in the preferred embodiment.
  • the comparison of the frequency of the rotor signal from the amplifier 17 with the reference signal from the oscillator 21 at the exclusive OR gate 19 results in an error output signal representing the difference between the rotor and reference signals. This error output signal is transmitted along conductive pathway 20 to the input of low pass filter 24."
  • the frequency of the rotor signal through amplifier 17 approaches the frequency of the reference signal.
  • the error signal is reduced to a very low frequency.
  • the pass band of the low pass filter 24 may be made extremely narrow. Only a very low frequency error signal may be passed through the filter 24 to the summing circuit 37, for further processing and transmission to the overspeed shutdown circuit 26 along pathway 27, for signaling an alarm condition.
  • This overspeed alarm system inherently has some delay due to the alarm system's use of the low pass filter 24.
  • the delay originates from the time that error signal falls below the threshold of the low pass filter 24 and continues until the time that power is disconnected from the drive motor by an alarm signal emanating from circuit 26.
  • This time delay is of great concern in the case of lightweight rotors which accelerate rapidly. In such a case, the rotor can be accelerated past its maximum rating, to a point where the frequency difference between the rotor and reference signals is greater than the bandpass of the low pass filter 24, so that this lightweight rotor may accelerate into overspeed avoiding detection by the alarm circuity.
  • the digital, phase detector 35 produces an output signal along pathway 36 which signifies an unambiguous response to the existence of an overspeed condition.
  • the output of digital phase detector 35 will have one polarity if the frequency of the signal from oscillator 21 exceeds the frequency of the signal from amplifier 17 and will have the opposite polarity if the frequency of the signal from amplifier 17 exceeds the frequency of the signal from oscillator 21.
  • the output signals from the amplifier 17 may be a symmetrical square wave; but, the output signals from the oscillator 21 are usually symmetrical square waves and therefore the edge of the square waves are more easily detected by the digital phase detector 35 than a low pass filter 24.
  • the output of this detector 35 is not as sharp as the output of the low pass filter 24, so the optimum overspeed detection system provides the output signals of the low pass filter 24 or the digital phase detector 35, whichever senses true alarm conditions, to the summing circuit 37.
  • the improved alarm signal system develops an input signal to the protection circuit 26 which is the reversed polarity of the normal negative polarity signal generated by the detector 35. This reversed polarity signal is detected by the overspeed shutdown circuit 26, and is conveyed to circuit 26 along pathway 36, through summing circuit 37, and along pathway 27.
  • the overspeed protection circuit 26 may be a silicon controlled rectifier (SCR) which is turned “on” when an alarm signal is generated at the output of the summing circuit 37. Turning “on” the SCR by tripping its gate diverts all current through the rectifier to ground and away from the power supply of the converter 29.
  • SCR silicon controlled rectifier
  • the improvement of this invention provides the structure for controlling the drive motor and shutting down the rotor even if control over the drive motor current and power fails.
  • the structure for providing an improved rotor overspeed safeguard system includes the circuitry shown generally as 100 within the dotted lines at the lower center of the Figure.
  • the improved rotor overspeed safeguard system includes a flip-flop or latch 102, which receives an alarm signal along pathway 30 at its set "S" input. This alarm signal to the input of latch 102 creates a logic change of state in the output "Q" of the latch 102. Once the output of latch 102 at "Q” changes state, it may be restored to its original setting only by a signal input to the reset "R" terminal over pathway 110. In the preferred embodiment, the latch 102 may only be reset by power transferred along pathway 70 through a manual control switch 115 or other switching device. The intent of this design is to require human intervention to disable an alarm signal once the alarm is sounded.
  • a motor tach signal is generated by a transducer 50 which detects the actual motor drive speed from drive motor 28 to produce a signal which is indicative of the true speed of the induction drive motor 28.
  • the motor tach signal generated by the output of the transducer 50 is conveyed to the input of the logic NOR gate 104 via conductive pathway 120.
  • the logic NOR gate 104 allows the motor tach signal to be transmitted along conductive pathway 60 for driving the inverter 29 which drives the motor 28 via pathways 40.
  • the motor tach signal must be transmitted on to the inverter 29 along pathway 60 to run the motor.
  • the logic gate 104 in the preferred embodiment, is a NOR gate. It may also be a HAND gate or an analog switch, such as a CD4051B, 4052B, or CD4053B COS/MOS analog multiplexer/demultiplexer manufactured by RCA.
  • Any data selector component such as a digitally controlled analog switch, may be substituted for the NOR gate as logic gate 104.) Inhibiting the tach signal shuts down the induction drive motor, even if the power supply remains- on, since without a tach signal, the induction drive motor 28 has insufficient torque and cannot function.
  • the preferred embodiment is illustrative of an improved rotor overspeed protection system.
  • the scope of the invention is not necessarily limited to the preferred embodiment. Many structural changes are possible and those changes are intended to be within the scope of this disclosure.
  • the tach signal is inhibited or diverted from the inverter 29 by means of a logic hardware system.
  • a computer which runs the motor drive during normal operation could be programmed for a subroutine which inhibits the tach signal from transducer 50 in the event of an overspeed alarm condition.

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  • Centrifugal Separators (AREA)

Abstract

Un système prioritaire sur les signaux de protection contre des survitesses invalide le signal tachimétrique provenant d'un tachimètre du rotor de l'appareil centrifuge, de telle sorte que le circuit de commande du moteur à onduleurs est incapable d'envoyer un signal d'entraînement du moteur multiphasé vers un moteur à induction à courant alternatif, et le rotor et le moteur de l'appareil centrifuge sont coupés, en réponse à un signal d'alarme provenant du circuit de protection contre les survitesses. Le signal prioritaire est produit de façon à assurer qu'une fois le circuit de protection contre les survitesses de l'appareil centrifuge a détecté une caractéristique d'un état d'alarme de survitesse du rotor, le signal tachimétrique qui entraîne l'onduleur est invalidé et retiré de la commande du moteur, de telle sorte qu'un moteur à induction à courant alternatif continuera de tourner par inertie jusqu'à s'arrêter même si la commande du courant du moteur à induction ne fonctionne pas correctement.
PCT/US1986/001488 1985-08-09 1986-07-16 Systeme prioritaire sur les signaux de protection contre des survitesses dans un appareil centrifuge WO1987000770A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US76428085A 1985-08-09 1985-08-09
US764,280 1985-08-09

Publications (1)

Publication Number Publication Date
WO1987000770A1 true WO1987000770A1 (fr) 1987-02-12

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Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US1986/001488 WO1987000770A1 (fr) 1985-08-09 1986-07-16 Systeme prioritaire sur les signaux de protection contre des survitesses dans un appareil centrifuge

Country Status (3)

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EP (1) EP0232324A1 (fr)
JP (1) JPS63500437A (fr)
WO (1) WO1987000770A1 (fr)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0321920A2 (fr) * 1987-12-23 1989-06-28 E.I. Du Pont De Nemours And Company Système centrifuge de commande avec deux processeurs
US5383838A (en) * 1991-01-07 1995-01-24 Beckman Instruments, Inc. Tachometer and rotor identification system for centrifuges
US5649893A (en) * 1996-05-22 1997-07-22 Hitachi Koki Co., Ltd. Centrifugal apparatus having series-implemented protection means
US6507161B2 (en) * 2000-04-14 2003-01-14 The Western States Machine Company Centrifuge motor control
US6602178B2 (en) * 2000-03-17 2003-08-05 Hitachi Koki Co., Ltd. Desk-top centrifuge having improved safety in the event of an operational failure
US6679820B2 (en) * 2000-04-11 2004-01-20 Kendro Laboratory Products, Lp Method for energy management and overspeed protection of a centrifuge
JP2019126807A (ja) * 2018-01-23 2019-08-01 エッペンドルフ アクチエンゲゼルシャフトＥｐｐｅｎｄｏｒｆ ＡＧ 要素の回転速度を監視するための方法および装置
CN111525497A (zh) * 2020-05-26 2020-08-11 广东博智林机器人有限公司 一种缓冲电路及电子设备

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3436637A (en) * 1966-07-29 1969-04-01 Beckman Instruments Inc Overspeed shutdown system for centrifuge apparatus
US3582699A (en) * 1969-06-12 1971-06-01 Damon Eng Inc Overspeed control for centrifuge
US4284931A (en) * 1979-03-14 1981-08-18 Beckman Instruments, Inc. Overspeed shutdown system for centrifuge apparatus
US4286203A (en) * 1979-03-14 1981-08-25 Beckman Instruments, Inc. Slip frequency control for variable speed induction motors
DE3305461A1 (de) * 1982-02-17 1983-08-25 Kabushiki Kaisha Kubota Seisakusho, Tokyo Automatischer diskriminator zum unterscheiden zwischen verschiedenen rotortypen
DE3436879A1 (de) * 1984-02-10 1985-08-14 Veb Kombinat Medizin- Und Labortechnik Leipzig, Ddr 7033 Leipzig Digitale ueberdrehzahl-schutzschaltung, insbesondere fuer zentrifugen

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3436637A (en) * 1966-07-29 1969-04-01 Beckman Instruments Inc Overspeed shutdown system for centrifuge apparatus
US3582699A (en) * 1969-06-12 1971-06-01 Damon Eng Inc Overspeed control for centrifuge
US4284931A (en) * 1979-03-14 1981-08-18 Beckman Instruments, Inc. Overspeed shutdown system for centrifuge apparatus
US4286203A (en) * 1979-03-14 1981-08-25 Beckman Instruments, Inc. Slip frequency control for variable speed induction motors
DE3305461A1 (de) * 1982-02-17 1983-08-25 Kabushiki Kaisha Kubota Seisakusho, Tokyo Automatischer diskriminator zum unterscheiden zwischen verschiedenen rotortypen
DE3436879A1 (de) * 1984-02-10 1985-08-14 Veb Kombinat Medizin- Und Labortechnik Leipzig, Ddr 7033 Leipzig Digitale ueberdrehzahl-schutzschaltung, insbesondere fuer zentrifugen

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0321920A2 (fr) * 1987-12-23 1989-06-28 E.I. Du Pont De Nemours And Company Système centrifuge de commande avec deux processeurs
EP0321920A3 (en) * 1987-12-23 1990-11-28 E.I. Du Pont De Nemours And Company Centrifuge control system having dual processors
US5383838A (en) * 1991-01-07 1995-01-24 Beckman Instruments, Inc. Tachometer and rotor identification system for centrifuges
US5752910A (en) * 1991-01-07 1998-05-19 Beckman Instruments, Inc. Variable threshold setting for rotor identification in centrifuges
US5649893A (en) * 1996-05-22 1997-07-22 Hitachi Koki Co., Ltd. Centrifugal apparatus having series-implemented protection means
US6602178B2 (en) * 2000-03-17 2003-08-05 Hitachi Koki Co., Ltd. Desk-top centrifuge having improved safety in the event of an operational failure
US6679820B2 (en) * 2000-04-11 2004-01-20 Kendro Laboratory Products, Lp Method for energy management and overspeed protection of a centrifuge
US6507161B2 (en) * 2000-04-14 2003-01-14 The Western States Machine Company Centrifuge motor control
JP2019126807A (ja) * 2018-01-23 2019-08-01 エッペンドルフ アクチエンゲゼルシャフトＥｐｐｅｎｄｏｒｆ ＡＧ 要素の回転速度を監視するための方法および装置
CN111525497A (zh) * 2020-05-26 2020-08-11 广东博智林机器人有限公司 一种缓冲电路及电子设备
CN111525497B (zh) * 2020-05-26 2022-06-24 广东博智林机器人有限公司 一种缓冲电路及电子设备

Also Published As

Publication number Publication date
EP0232324A1 (fr) 1987-08-19
JPS63500437A (ja) 1988-02-18

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