WO2009053519A1 - Safety coupling for a frequency converter controlled motor drive - Google Patents

Safety coupling for a frequency converter controlled motor drive Download PDF

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Publication number
WO2009053519A1
WO2009053519A1 PCT/FI2008/000116 FI2008000116W WO2009053519A1 WO 2009053519 A1 WO2009053519 A1 WO 2009053519A1 FI 2008000116 W FI2008000116 W FI 2008000116W WO 2009053519 A1 WO2009053519 A1 WO 2009053519A1
Authority
WO
WIPO (PCT)
Prior art keywords
bridge
frequency converter
control pulses
branch
controlled
Prior art date
Application number
PCT/FI2008/000116
Other languages
French (fr)
Inventor
Jari Pekola
Tapio Haring
Petri MÄKI-ONTTO
Original Assignee
Abb Oy
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 Abb Oy filed Critical Abb Oy
Publication of WO2009053519A1 publication Critical patent/WO2009053519A1/en

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Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K5/00—Casings; Enclosures; Supports
    • H02K5/04—Casings or enclosures characterised by the shape, form or construction thereof
    • H02K5/12—Casings or enclosures characterised by the shape, form or construction thereof specially adapted for operating in liquid or gas
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P25/00—Arrangements or methods for the control of AC motors characterised by the kind of AC motor or by structural details
    • H02P25/16—Arrangements or methods for the control of AC motors characterised by the kind of AC motor or by structural details characterised by the circuit arrangement or by the kind of wiring
    • H02P25/22—Multiple windings; Windings for more than three phases
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K5/00—Casings; Enclosures; Supports
    • H02K5/04—Casings or enclosures characterised by the shape, form or construction thereof
    • H02K5/12—Casings or enclosures characterised by the shape, form or construction thereof specially adapted for operating in liquid or gas
    • H02K5/136—Casings or enclosures characterised by the shape, form or construction thereof specially adapted for operating in liquid or gas explosion-proof
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P27/00—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage
    • H02P27/04—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P9/00—Arrangements for controlling electric generators for the purpose of obtaining a desired output
    • H02P9/14—Arrangements for controlling electric generators for the purpose of obtaining a desired output by variation of field
    • H02P9/26—Arrangements for controlling electric generators for the purpose of obtaining a desired output by variation of field using discharge tubes or semiconductor devices
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P2207/00—Indexing scheme relating to controlling arrangements characterised by the type of motor
    • H02P2207/07—Doubly fed machines receiving two supplies both on the stator only wherein the power supply is fed to different sets of stator windings or to rotor and stator windings
    • H02P2207/076—Doubly fed machines receiving two supplies both on the stator only wherein the power supply is fed to different sets of stator windings or to rotor and stator windings wherein both supplies are made via converters: especially doubly-fed induction machines; e.g. for starting

Definitions

  • the object of the invention is a safety coupling in a frequency converter controlled motor drive according to the preamble of Claim 1.
  • Explosive atmospheres appear in the process industry, particularly in oil and gas refining industry. Conveyors, pumps and other continuously or periodically operating drives are frequently used as actuators in these industries. Among the motors driving actuators, frequency converter controlled motors with small air gaps may be particularly problematic.
  • Safety measures include the use of mechanical or corresponding safety guards to protect the equipment that may cause an unforeseen increase in the total accident risk.
  • bearing and shaft voltages in a motor or generator caused by a voltage source frequency converter may endanger the bearings and may also directly ignite an explosion. Removal of these above-mentioned unwanted voltages for example by using various filters or insulation of bearing surfaces is expensive and inconvenient.
  • the objective of the invention is to create a new, safe and functionally reliable frequency converter controlled motor drive for dangerous areas.
  • the invention is characterized by the features specified in the characteristics section of Claim 1.
  • the characteristics of some other preferred embodiments of the invention are characterized by dependent claims.
  • an actuator in an explosive atmosphere is driven by a motor that is controlled with a dual bridge inverter (DBI), in which the motor output of the frequency converter consists of two synchronized branches with opposite phases, both of which may consist of one or more parallel inverter bridges.
  • the motor output branches are controlled with simultaneous control signals with opposite phases, created in a control unit common to both branches. Due to the simultaneousness requirement of control signals it is essential that the motor output branches are not controlled with higher level signals generally used for the so-called master-slave drives, such as current, frequency, speed or moment, the use of which does not guarantee simultaneous branch connections, as it is well known.
  • Separate cables will be used to connect the branches of the said motor output to the two branch windings of the motor driving the said actuator.
  • the polarity of one of these branch windings is reversed.
  • the said branch windings may consist of one or more internal branches.
  • a dual-bridge inverter DBI can be utilized to prevent common-mode voltages from accessing the electrical machine or an actuator driven by the machine.
  • the stator winding will have an even number of branches, in which case the first bridge is used to control the odd branches of each branch pair, and the other bridge will supply the even branch of each branch pair, the control signals to the even branch being reverse to and simultaneous with the control pulses of the first bridge.
  • the frequency converter is connected to a power grid with a dual network bridge including a first network bridge controlled by the first control pulses of the network bridge, and a second network bridge controlled by the second control pulses of the network bridge, the second control pulses being reverse to the first control pulses.
  • a dual network bridge including a first network bridge controlled by the first control pulses of the network bridge, and a second network bridge controlled by the second control pulses of the network bridge, the second control pulses being reverse to the first control pulses.
  • FIG. 1 illustrates a connection principle used in the invention
  • FIG. 1 is a schematic illustration of a coupling to enable a frequency converter to supply and control an electrical machine, implementing a solution according to the invention.
  • the frequency converter includes a network rectifier 4 connected to an alternating-current network 2 and used to create a direct- current voltage into the frequency converter's intermediate circuit 6.
  • a capacitor 8 has been connected to the intermediate circuit between the intermediate circuit conductors 10 and 12 using a known method.
  • direct current is conducted from the intermediate circuit to the inverter component 15, consisting of two identical inverters 14 and 16 that contain a six-pulse bridge, and using IGBT semiconductor switches.
  • Pulse width modulation is used to convert direct voltage into alternating voltage by connecting the positive and negative voltages of the direct voltage to the stator windings of the electrical machine so that an alternating voltage according to the control is created in the windings.
  • Alternating voltage consists of voltage pulses.
  • the motor stator winding consists of two separate branch windings, in which case the first branch winding 18 consists of windings U 1 , V 1 and W 1 and the second branch winding 20 consists of windings U 2 , V 2 , and W 2 .
  • Branch windings 18 and 20 are parallel connected so that their conductors do not touch at any point.
  • the first branch winding 18 is supplied by the inverter 14, and the other branch winding 20 is supplied by the inverter 16.
  • the first and second branch winding are identical, but they are supplied from opposite ends. This is illustrated by the schematic winding diagram in Figure 1.
  • the first ends 22, 24 and correspondingly 26 (marked with black dots) of the windings Ul, Vl and Wl of the first branch winding 18 have been connected to the output of the inverter 14, and the opposing ends have been connected to the star point 27.
  • the first ends (marked with black dots) of the windings of the second branch winding 20 have been connected to the star point 28, and the opposing ends have been connected to the output of the inverter 16.
  • Inverters 14 and 16 are controlled by the control device 30.
  • the control signals generated by the device are conducted by cable 32 to the semiconductor switches of inverter 14.
  • the same control signals are conducted by cable 34 to the reverse operator 36 and further with cable 38 to the semiconductor switches of inverter 16.
  • the voltages supplied by inverters 14 and 16 to branch windings 18 and 20 are therefore of the same magnitude but opposite phase, resulting in the branch windings inducing a unidirectional field.
  • Both inverters 14 and 16 generate common-mode voltages that are due to the sum of voltages over windings not equaling to zero at all times.
  • the switches of inverters 14 and 16 are simultaneously controlled in the opposite phases, both create common-mode voltages of identical magnitude, canceling each other out.
  • FIG 2 contains a schematic illustration of a solution according to the invention.
  • Pump 42 driven by the motor 44 has been fitted inside the explosive atmosphere 40.
  • Motor rotor 46 is bearing-mounted with bearings 50 to the motor end plates 48.
  • Motor 44 is controlled by an inverter as shown in connection with Figure 1.
  • Inverters 14 and 16 of the inverter component 15 have been installed outside the explosive atmosphere 40, and the motor is supplied by motor cables 52 taken into the explosive atmosphere.

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Control Of Multiple Motors (AREA)
  • Control Of Ac Motors In General (AREA)
  • Control Of Electric Motors In General (AREA)

Abstract

The object of the invention is a coupling arrangement when using a frequency converter (14, 16) to control an electrical machine (44) connected to an actuator, at least the electrical machine (44) being located in an explosive atmosphere (40). High frequency modulation is used to create an alternating frequency voltage in the electrical machine (44) connected to a frequency converter (14, 16). At least two branches isolated from each other exist in the motor stator winding. The frequency converter is a dual bridge inverter consisting of two essentially identical bridges (14, 16). The first bridge (14) is used to supply the first branch winding of the stator through the first supply cable, and the second bridge (16) is used to supply the second branch winding through the second supply cable. The first bridge (14) is controlled by the first control pulses and the second bridge (16) is controlled by the second control pulses, the second control pulses being simultaneous with and reverse to the first control pulses.

Description

SAFETY COUPLING FOR A FREQUENCY CONVERTER CONTROLLED MOTOR DRIVE
The object of the invention is a safety coupling in a frequency converter controlled motor drive according to the preamble of Claim 1.
In explosive atmospheres, potentially dangerous situations must be prevented and the damage caused by any accidents must be limited with safety measures to a minimum. Design guidelines and standards contain instructions and regulations that must be met when working in a danger zone and when manufacturing or operating machines in explosive atmospheres or in the vicinity of such atmospheres. For example, an electrical machine using brushes, the use of which may in normal operation include spark formation, cannot be used in explosive atmospheres.
Explosive atmospheres appear in the process industry, particularly in oil and gas refining industry. Conveyors, pumps and other continuously or periodically operating drives are frequently used as actuators in these industries. Among the motors driving actuators, frequency converter controlled motors with small air gaps may be particularly problematic.
Safety measures include the use of mechanical or corresponding safety guards to protect the equipment that may cause an unforeseen increase in the total accident risk. For example, bearing and shaft voltages in a motor or generator caused by a voltage source frequency converter may endanger the bearings and may also directly ignite an explosion. Removal of these above-mentioned unwanted voltages for example by using various filters or insulation of bearing surfaces is expensive and inconvenient.
The objective of the invention is to create a new, safe and functionally reliable frequency converter controlled motor drive for dangerous areas. In order to achieve this, the invention is characterized by the features specified in the characteristics section of Claim 1. The characteristics of some other preferred embodiments of the invention are characterized by dependent claims.
According to the invention, an actuator in an explosive atmosphere is driven by a motor that is controlled with a dual bridge inverter (DBI), in which the motor output of the frequency converter consists of two synchronized branches with opposite phases, both of which may consist of one or more parallel inverter bridges. The motor output branches are controlled with simultaneous control signals with opposite phases, created in a control unit common to both branches. Due to the simultaneousness requirement of control signals it is essential that the motor output branches are not controlled with higher level signals generally used for the so-called master-slave drives, such as current, frequency, speed or moment, the use of which does not guarantee simultaneous branch connections, as it is well known. Separate cables will be used to connect the branches of the said motor output to the two branch windings of the motor driving the said actuator. The polarity of one of these branch windings is reversed. The said branch windings may consist of one or more internal branches. With the invention, a dual-bridge inverter (DBI) can be utilized to prevent common-mode voltages from accessing the electrical machine or an actuator driven by the machine.
According to one embodiment of the invention, the stator winding will have an even number of branches, in which case the first bridge is used to control the odd branches of each branch pair, and the other bridge will supply the even branch of each branch pair, the control signals to the even branch being reverse to and simultaneous with the control pulses of the first bridge.
According to another embodiment of the invention, the frequency converter is connected to a power grid with a dual network bridge including a first network bridge controlled by the first control pulses of the network bridge, and a second network bridge controlled by the second control pulses of the network bridge, the second control pulses being reverse to the first control pulses. This will also enable reversing the so-called front end common-mode voltage.
In the following, the invention will be described in detail with the help of certain embodiments by referring to the enclosed drawings, where
— Figure 1 illustrates a connection principle used in the invention and
- Figure 2 illustrates an application according to the invention.
Figure 1 is a schematic illustration of a coupling to enable a frequency converter to supply and control an electrical machine, implementing a solution according to the invention. The frequency converter includes a network rectifier 4 connected to an alternating-current network 2 and used to create a direct- current voltage into the frequency converter's intermediate circuit 6. A capacitor 8 has been connected to the intermediate circuit between the intermediate circuit conductors 10 and 12 using a known method. In this embodiment of the invention, direct current is conducted from the intermediate circuit to the inverter component 15, consisting of two identical inverters 14 and 16 that contain a six-pulse bridge, and using IGBT semiconductor switches. Pulse width modulation is used to convert direct voltage into alternating voltage by connecting the positive and negative voltages of the direct voltage to the stator windings of the electrical machine so that an alternating voltage according to the control is created in the windings. Alternating voltage consists of voltage pulses. When one six-pulse bridge is used to supply the motor stator windings, momentary switch positions have the effect that the common-mode voltage over the motor windings is not always zero as it is for a sinusoidally varying three-phase voltage. According to the invention, the motor stator winding consists of two separate branch windings, in which case the first branch winding 18 consists of windings U1, V1 and W1 and the second branch winding 20 consists of windings U2, V2, and W2. Branch windings 18 and 20 are parallel connected so that their conductors do not touch at any point. The first branch winding 18 is supplied by the inverter 14, and the other branch winding 20 is supplied by the inverter 16. The first and second branch winding are identical, but they are supplied from opposite ends. This is illustrated by the schematic winding diagram in Figure 1. The first ends 22, 24 and correspondingly 26 (marked with black dots) of the windings Ul, Vl and Wl of the first branch winding 18 have been connected to the output of the inverter 14, and the opposing ends have been connected to the star point 27. Correspondingly, the first ends (marked with black dots) of the windings of the second branch winding 20 have been connected to the star point 28, and the opposing ends have been connected to the output of the inverter 16.
Inverters 14 and 16 are controlled by the control device 30. The control signals generated by the device are conducted by cable 32 to the semiconductor switches of inverter 14. The same control signals are conducted by cable 34 to the reverse operator 36 and further with cable 38 to the semiconductor switches of inverter 16. The voltages supplied by inverters 14 and 16 to branch windings 18 and 20 are therefore of the same magnitude but opposite phase, resulting in the branch windings inducing a unidirectional field. Both inverters 14 and 16 generate common-mode voltages that are due to the sum of voltages over windings not equaling to zero at all times. When the switches of inverters 14 and 16 are simultaneously controlled in the opposite phases, both create common-mode voltages of identical magnitude, canceling each other out.
The sum of the output voltages of inverters 14 and 16 is zero at all times, so the inverter operation will cause no common-mode voltage. No currents caused by common-mode voltage are thus induced in the magnetic circuit of the motor. As a consequence, no circulating, spark-inducing currents closing their circuit through the bearings exist in the actuator frame components fastened to the stator and rotor of the motor. As there is no common-mode voltage, no capacitive coupled so-called bearing voltages causing danger of explosion will emerge between the motor components.
Figure 2 contains a schematic illustration of a solution according to the invention. Pump 42 driven by the motor 44 has been fitted inside the explosive atmosphere 40. Motor rotor 46 is bearing-mounted with bearings 50 to the motor end plates 48. Motor 44 is controlled by an inverter as shown in connection with Figure 1. Inverters 14 and 16 of the inverter component 15 have been installed outside the explosive atmosphere 40, and the motor is supplied by motor cables 52 taken into the explosive atmosphere.
In the above, the invention has been described with the help of certain embodiments. However, the description should not be considered as limiting the scope of patent protection; the embodiments of the invention may vary within the scope of the following claims.

Claims

1. A coupling arrangement when using a frequency converter (4, 14, 16) to control an electrical machine (44) connected to an actuator, at least the electrical machine (44) being located in an explosive atmosphere (40), high frequency modulation being used to create an alternating frequency voltage in the electrical machine (44) connected to the frequency converter (4, 14, 16), characterized in that the motor stator winding contains at least two branches (18, 20) isolated from each other; in that the frequency converter is a dual-bridge inverter consisting of two essentially identical bridges (14, 16); in that the first bridge (14) supplies the first branch winding (18) of the stator through the first supply cable and the second bridge (16) supplies the second branch winding (20) of the stator through the second supply cable; and in that the first bridge (14) with the first control pulses (32) and the second bridge (16) is controlled with the second simultaneous control pulses (38) being reverse to the first control pulses.
2. Arrangement according to Claim 1, characterized in that there are an even number of branches (18, 20) in the stator winding, and in that the first bridge is used to control the odd branches of each branch pair and the second bridge supplies the even branch of each branch pair, the control pulses of the second bridge being reverse to the control pulses of the first bridge.
3. Arrangement according to Claim 1, characterized in that the frequency converter is connected to a power grid with a dual network bridge including a first network bridge controlled by the first control pulses of the network bridge, and a second network bridge controlled by the second control pulses of the network bridge, the second control pulses being reverse to the first control pulses.
4. Arrangement according to Claim 1, characterized in that the frequency converter (4, 14, 16) is located outside the explosive atmosphere (40), electrical energy being conducted by motor cables (52) from the frequency converter to the motor (44) located in the explosive atmosphere (40).
PCT/FI2008/000116 2007-10-26 2008-10-24 Safety coupling for a frequency converter controlled motor drive WO2009053519A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FI20070814 2007-10-26
FI20070814A FI20070814L (en) 2007-10-26 2007-10-26 Safety coupling of a frequency converter-controlled motor operation

Publications (1)

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WO2009053519A1 true WO2009053519A1 (en) 2009-04-30

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WO (1) WO2009053519A1 (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2731253A3 (en) * 2012-09-19 2016-03-02 Kabushiki Kaisha Toshiba System for driving electromagnetic appliance and motor driven vehicle
WO2019115350A1 (en) * 2017-12-14 2019-06-20 Continental Automotive Gmbh Electrical drive assembly, in particular for operating a hybrid electric vehicle/electric vehicle

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2004036721A1 (en) * 2002-10-21 2004-04-29 Abb Oy Arrangement for protecting an electric machine

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2004036721A1 (en) * 2002-10-21 2004-04-29 Abb Oy Arrangement for protecting an electric machine

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
"Industry Applications Conference, 1999, Oct.", article VON JOUANNE A. ET AL: "A reduced switch dual-bridge inverter topology for the mitigation of bearing currents, EMI and DC-link voltage variations", pages: 1945 - 1949, XP010355130 *
MAKI-ONTTO, P ET AL.: "Reduction of capacitive and induced shaft voltages in an induction motor drive using dual-bridge inverter approach", 'ELECTRICAL ENGINEERING' (2006) 88, IN: ARCHIV FUR ELEKTROTECHNIK, August 2006 (2006-08-01), pages 465 - 472, XP019419650 *
WANG, F: "Motor shaft voltages and bearing currents and their reduction in multilevel medium-voltage PWM voltage-source-inverter drive applications", INDUSTRY APPLICATIONS, IEEE TRANSACTIONS ON, vol. 36, 2000, pages 1336 - 1341, XP011022852 *

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2731253A3 (en) * 2012-09-19 2016-03-02 Kabushiki Kaisha Toshiba System for driving electromagnetic appliance and motor driven vehicle
US9379597B2 (en) 2012-09-19 2016-06-28 Kabushiki Kaisha Toshiba System for driving electromagnetic appliance and motor driven vehicle
WO2019115350A1 (en) * 2017-12-14 2019-06-20 Continental Automotive Gmbh Electrical drive assembly, in particular for operating a hybrid electric vehicle/electric vehicle

Also Published As

Publication number Publication date
FI20070814A0 (en) 2007-10-26
FI20070814L (en) 2009-04-27

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