MAGNETIC BEARING FAULT-TOLERANT DRIVE SYSTEM
TECHNICAL FIELD
[0001] The present invention relates generally to electronic fault protection systems,
and more particularly, to a magnetic bearing drive system including electronic fault
protection architecture.
BACKGROUND
[0002] Rotational machines implement contact-less active magnetic bearings in
widespread applications ranging from oil-free compressors, pumps, flywheels for energy
storage, and rotational shafts. The bearing itself is levitated in a contact-less manner in
response to realizing an electromagnetic filed generated by an electronic magnetic bearing
driver circuit that includes a plurality of power electronic devices. Failure of one or more of
the power electronic devices such as an open-circuit fault, for example, can result in the loss
of the magnetic bearing levitation. A loss in bearing levitation at the time when a rotating
shaft (e.g., a rotor) is rotating at a high speed can cause severe damage to the mechanical
components.
SUMMARY
[0003] According to an embodiment, an electronic magnetic bearing fault-tolerant
drive module includes a first plurality of switching elements and a second plurality of
switching elements. At least one winding is interposed between the first plurality of
switching elements and the second plurality of switching elements. The first and second
switching elements are configured to selectively operate in a first mode and a second mode to
generate an electromagnetic field. The electronic magnetic bearing fault-tolerant drive
module is configured to detect one or more electrical faults including an open-circuit fault of
at least one of the first and second switching elements.
[0004] In addition to one or more of the features described above, or as an alternative,
further embodiments include:
[0005] a feature, wherein a diode connected across each switching element among the
first and second plurality of switching elements to form a plurality of bi-directional phase-leg
circuits;
[0006] a feature, wherein the first mode is configured to generate at least one winding
current in a first direction through the at least one winding in response to receiving a first
PWM output signal, and to generate the at least one winding current in a second direction
opposite the first direction through the at least one winding in response to receiving a second
PWM output signal;
[0007] a feature, wherein a first winding is interposed between a first bi-directional
phase-leg circuit and a second bi-directional phase leg circuit forming a first H-bridge circuit,
and a second winding is interposed between a second bi-directional phase-leg circuit and a
third bi-directional phase leg circuit forming a second H-bridge circuit;
[0008] a feature, wherein the first H-bridge circuit and the second H-bridge circuit
share a single common phase-leg, and wherein the first H-bridge circuit is configured to
control the first winding current through the first winding and the second H-bridge circuit is
configured to control a second winding current through the second winding, the second
winding current controlled to have an opposite direction with respect to the first winding
current; and
[0009] a feature, wherein each bi-directional phase-leg circuit includes a first
switching element configured to conduct current based on the first mode and inhibit current
based on the second mode, and a second switching element configured to inhibit current
based on the first mode and conduct current based on the second mode.
[0010] According to another embodiment, an electronic magnetic bearing faulttolerant
drive system includes an electronic magnetic bearing fault-tolerant drive module
configured to selectively operate in a first mode in response to receiving the first PWM
output signal and a second mode in response to receiving the second PWM output signal.
The electronic magnetic bearing fault-tolerant drive system further includes an electronic
fault detection module in electrical communication with the electronic magnetic bearing
fault-tolerant drive module. The electronic fault detection module is configured to output a
fault command signal in response to detecting an electrical fault of the electronic magnetic
bearing fault-tolerant drive system, where the fault command signal initiates transition from
the first mode to the second mode.
[0011] In addition to one or more of the features described above, or as an alternative,
further embodiments include:
[0012] a feature, wherein an electronic fault-tolerant current controller module
configured to selectively output a first PWM output signal and a second PWM output signal;
[0013] a feature, wherein in response to receiving the fault command signal, the
electronic fault-tolerant current controller module disconnects the first PWM output signal
and outputs the second PWM output signal to switch the electronic magnetic bearing faulttolerant
drive module from the first mode to the second mode;
[0014] a feature, wherein the magnetic bearing fault-tolerant drive module includes at
least one winding configured to generate an electromagnetic field in response to receiving a
winding current flowing in a first direction;
[0015] a feature, wherein the fault detection module detects an open-circuit fault of
the magnetic bearing fault-tolerant drive module based on a comparison between the at least
one winding current and a threshold value;
[0016] a feature, wherein the electronic magnetic bearing fault-tolerant drive module
includes a plurality of bi-directional phase-leg circuits connected to the at least one winding
to form at least one H-bridge circuit;
[0017] a feature, wherein the bi-directional phase-leg circuits are configured to
generate the winding current in a first direction in response to receiving the first PWM output
signal having a first phase and to generate the winding current in a second direction opposite
the first direction in response to receiving the second PWM output signal having a second
phase opposite the first phase;
[0018] a feature, wherein the plurality of bi-directional phase-leg circuits each
includes a first switching element configured to generate current based on the first mode and
inhibit current based on the second mode, and a second switching element configured to
inhibit current based on the first mode and generate current based on the second mode; and
[0019] a feature, wherein the at least one electrical fault includes an open-circuit fault
induced in response to a failure of the first switching element.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] The subject matter which is regarded as the invention is particularly pointed
out and distinctly claimed in the claims at the conclusion of the specification. The foregoing
and other features, and advantages of the invention are apparent from the following detailed
description taken in conjunction with the accompanying drawings in which:
[0021] FIG. 1A is an electrical schematic diagram of a fault-tolerant magnetic bearing
drive module according to an exemplary embodiment;
[0022] FIG. IB is a an electrical schematic diagram of the fault-tolerant magnetic
bearing drive module operating in a first mode according to an exemplary embodiment;
[0023] FIG. 1C is a an electrical schematic diagram of the fault-tolerant magnetic
bearing drive module operating in a second mode according to an exemplary embodiment;
[0024] FIG. 2 is a block diagram of a magnetic bearing fault-tolerant drive control
system according to an exemplary embodiment;
[0025] FIG. 3 is a flow diagram illustrating a fault identification procedure performed
by the magnetic bearing fault-tolerant drive system according to an exemplary embodiment;
and
[0026] FIG. 4 is a signal diagram illustrating operation of a magnetic bearing faulttolerant
drive system according to an exemplary embodiment.
DETAILED DESCRIPTION OF THE INVENTION
[0027] The following description is merely exemplary in nature and is not intended to
limit the present disclosure, its application or uses. It should be understood that throughout
the drawings, corresponding reference numerals indicate like or corresponding parts and
features. As used herein, the term module refers to processing circuitry that may include an
application specific integrated circuit (ASIC), an electronic circuit, a processor (shared,
dedicated, or group) and memory that executes one or more software or firmware programs, a
combinational logic circuit, and/or other suitable components that provide the described
functionality.
[0028] A magnetic bearing fault-tolerant drive system includes an electronic faulttolerant
magnetic bearing drive module configured to selectively operate in a first mode, i.e.,
a normal mode, and a second mode, i.e., an auxiliary mode. The fault-tolerant magnet
bearing drive module may include a three-phase converter and a plurality of switching
elements such as transistors, for example, to drive the three-phase converter. When operating
in the normal mode, a first plurality of switching elements is activated to generate a winding
current in a first direction, which in turn drives the three-phase converter and generates an
electromagnetic force that levitates the bearing of the rotary system.
[0029] When the auxiliary mode is selected (e.g., in response to detecting electrical
fault), the first plurality of switching elements is deactivated and a second plurality of
switching elements are activated to drive the three-phase converter. In this manner, the
winding current is generated in a second direction different from the first direction, while still
driving the three-phase converter. Since electromagnetic forces are determined by the
absolute value of winding current (i.e., is independent from the direction of the winding
current), a similar electromagnetic force can still be generated using the auxiliary mode and
levitation of the bearing can be maintained.
[0030] Turning now to FIG. 1A, an electrical schematic diagram of an electronic
fault-tolerant magnetic bearing drive module 100. According to a non-limiting embodiment,
the electronic fault-tolerant magnetic bearing drive module 100 is constructed as full-bridge
three-phase converter. The electronic fault-tolerant magnetic bearing drive module 100
includes a first bi-directional phase-leg circuit 102a, a second bi-directional phase-leg circuit
102b, and a third bi-directional phase-leg circuit 102c. The two windings' current (IA, Ic) are
drive by the three phase-leg circuits 102a- 102c, which can be viewed as two H-bridges 103a-
103b, which share a single common phase-leg. Each H-bridge circuit 103a- 103b is
configured to generate a respective winding current (IA, Ic) capable of flowing in first and
second opposing directions. Although three bi-directional phase-leg circuits 102a-102c are
shown, it is appreciated that bi-directional circuits with more than three phase-legs can be
used. For example, the electronic fault-tolerant magnetic bearing drive module 100 can be
constructed with two bi-directional phase-leg circuits or four bi-directional phase-leg circuits
without changing the scope of the invention.
[0031] The first bi-directional phase-leg circuit 102a includes a first switching
element 104a and a second switching element 104b. The second bi-directional phase-leg
circuit 102b includes a third switching element 104c and fourth switching element 104d. The
third bi-directional phase-leg circuit 102c includes a fifth switching element 104e and sixth
switching element 104f. According to a non-limiting embodiment, the switching elements
are insulated-gate bipolar transistors (IGBT). It is appreciated, however, that other
semiconductor switching elements can be used including, but not limited, metal oxide field
effect transistors (MOSFET). The electronic fault-tolerant magnetic bearing drive module
100 also includes diodes 106 connected across the collector and emitter of each switching
element 104a-104f. In this manner, the winding currents IA C can each be generated in
opposing first and second directions based on the phase (i.e., positive or negative) of the
signal that drives the switching elements 104a-104f as discussed in greater detail below.
[0032] Each bi-directional phase-leg circuit 102a- 102c is center-tapped with a
respective winding. For example, a first winding 108a includes a first end and a second end.
The first end is connected between to the emitter of the first switching element 104a and the
collector second switching element 104b. The second end is connected to the emitter of the
third switching element 104c and the collector of the fourth switching element 104d.
Accordingly, a first H-bridge circuit 103a is formed using the first winding 108a. Similarity,
a second winding 108b includes a first end and a second end. The first end is connected the
emitter of the third switching element 104c and the collector of the fourth switching element
104d. The second end is connected to the emitter of the fifth switching element 104e and the
collector of the sixth switching element 104f. Accordingly, a second H-bridge circuit 103b is
formed using the second winding 108b. According to an embodiment, the two H-bridge
circuits 103a-103b share a common phase-leg, e.g., phase-leg 102-b.
[0033] Turning now to FIG. IB, the electronic fault-tolerant magnetic bearing drive
module 100 is illustrated operating in a first mode, e.g., a normal mode. According to an
embodiment, each bi-directional phase-leg circuit 102a- 102c includes at least one activated
switching element and at least one deactivated switching element. The darkened lines
indicate the switching elements that are activated during the normal mode. In this case, for
example, the first switching element 104a, the fourth switching element 104d and the fifth
switching element 104e are in deactivated, while the second switching element 104b, the
third switching element 104c, and the sixth switching element 104f are activated. The
deactivated switching elements 104a, 104d, 104e inhibit current flow, while the activated
switching elements 104b, 104c and 104f conduct current flow. Accordingly, the activated
second switching element 104b and third switching element 104c generate and control a first
winding current IA flowing in a first direction through the first winding 108a. The activated
third switching element 104c and sixth switching element 104f generate and control a second
winding current Ic flowing in a second direction through the second winding 108b. The
second winding current Ic flows in a direction opposite the first direction of the first winding
current IA. The first winding current IA induces a first electromagnetic field in response to
flowing through the first winding 108a and the second winding current Ic generates a second
electromagnetic field in response to flowing through the second winding 108b. The first and
second electromagnetic fields magnetically levitate one or more bearings in a contact-less
manner.
[0034] Turning now to FIG. IC, the electronic fault-tolerant magnetic bearing drive
module 100 is illustrated operating in a second mode, e.g., an auxiliary mode. According to
at least one embodiment, the electronic fault-tolerant magnetic bearing drive module 100 is
switched from the normal mode to the auxiliary mode in response to detecting one or more
circuit faults including, but not limited to, an open-circuit fault. The open-circuit fault can
occur, for example, when one or more switching elements 104b, 104c, 104f activated during
the normal operating mode fails. According to an embodiment, each bi-directional phase-leg
circuit 102a- 102c includes at least one activated switching element and at least one
deactivated switching element. The darkened lines indicate the switching elements that are
activated during the auxiliary mode, while the non-darkened lines indicated the switching
elements that are de-activated.
[0035] When operating in the auxiliary mode, for example, the second switching
element 104b, the third switching element 104c, and the sixth switching element 104f are
deactivated, and the first switching element 104a, the fourth switching element 104d and the
fifth switching element 104e are activated. In this case, the activated switching elements
104a, 104d, 104e conduct current flow while the deactivated switching elements 104b, 104c
and 104f inhibit current flow. Accordingly, the activated first switching element 104a and
fourth switching element 104d generate and control a first winding current IA' flowing in a
first direction through the first winding 108a. The activated third switching element 104d
and fifth switching element 104e generate and control a second winding current Ic' flowing in
a second direction through the second winding 108b. The second winding current Ic' flows in
a direction opposite the first direction of the first winding current IA. Moreover, the first
winding current IA' generated during the auxiliary mode flows in an opposite direction (i.e.,
negative phase) with respect to the first winding current IA generated during the normal
mode. Similarly, the second winding current Ic' generated during the auxiliary mode flows in
an opposite direction (i.e., negative phase) with respect to the second winding current Ic
generated during the normal mode.
[0036] The first winding current IA' induces a first electromagnetic field in response
to flowing through the first winding 108a and the second winding current Ic' generates a
second electromagnetic field in response to flowing through the second winding 108b. The
electromagnetic fields are determined by the absolute value of winding current IA', Ic ' . Since
the magnetic bearing force is independent from the direction of the winding currents IA, IA',
Ic, and Ic', both the normal mode and the auxiliary mode can generate similar levitation
forces. Accordingly, one or more bearings can be maintained in a contact-less levitation state
without interruption when switching from the normal mode to the auxiliary mode.
[0037] Turning now to FIG. 2, an electronic magnetic bearing fault-tolerant drive
control system 200 is illustrated according to a non-limiting embodiment. The magnetic
bearing fault-tolerant drive system 200 implements an electronic fault-tolerant magnetic
bearing drive module 100 and is configured to detect various electrical faults including, for
example, an open-circuit fault caused by one or more failed switching elements 102a-102f.
In response to detecting the fault, the magnetic bearing fault-tolerant drive system 200 is
configured to control operation of the fault-tolerant magnetic bearing drive module 100. For
example, the magnetic bearing fault-tolerant drive system 200 is configured to switch the
fault-tolerant magnetic bearing drive module 100 from the normal mode to the auxiliary
mode in response to detecting an open-circuit fault.
[0038] The magnetic bearing fault-tolerant drive control system 200 includes an
electronic magnetic bearing fault-tolerant drive module 100, and electronic position control
module 202, an electronic fault-tolerant current controller module 204, and an electronic fault
detection module 206. The fault-tolerant magnetic bearing drive module 100 operates
according to the descriptions discussed in detail above. The position control module 202
determines a position error of a shaft coupled to a levitated bearing. In this manner, the
position of the bearing, and thus the shaft, dictates the position error. Based on the magnetic
force rated value, bias current I_bias is pre-determined, and in turn generates a first reference
winding current (ia_ref) and a second reference winding current (ic_ref).
[0039] The fault-tolerant current controller module 204 is in signal communication
with the position control module 202 to receive the first reference winding current signal
(ia_ref) and the second reference winding current signal (ic_ref). The fault-tolerant current
controller module 204 also receives winding current signals from one or more current sensors
configured to detect the winding currents flowing through the windings included in the faulttolerant
drive module 100. As illustrated in FIG. 2, for example, the fault-tolerant current
controller module 204 receives a first winding current signal (ia) indicative of the first
winding current (Ia) and a second winding current signal (ic) indicative of the second
winding current (Ic).
[0040] The fault-tolerant current controller module 204 further includes a first current
regulator unit 208a, a second current regulator unit 208b, a first pulse width modulation
(PWM) channel driver 210a, a second PWM channel driver 210b, and a PWM channel mixer
212. The first current PWM channel driver 210a generates a first PWM output signal 214a
that drives switching elements 104b, 104c, and 104f activated during the normal mode. The
second PWM channel driver 210b generates a second PWM output signal 214b that drives
switching elements 104a, 104d, and 104e activated during the auxiliary mode. The first
current regulator unit 208a receives first and second reference current signals (ia_ref), (ic_ref)
in positive phase, while the second current regulator unit 208b receives first and second
reference current signals (-ia_ref), (-ic_ref) in negative phase (i.e., inverse signals). Based on
a comparison between the reference current signals (ia_ref, - ia_ref, ic_ref, - ic_ref) and the
first and second winding current signals (IA, IC), the first and second PWM channel drivers
210a, 210b generate respective first and second PWM output signals 214a, 214b. A first
PWM channel 216a is in signal communication with gate terminals of the normal mode
switching elements 104b, 104c, and 104f and a second PWM channel 216b is in signal
communication with gate terminals of the auxiliary mode switching elements 104a, 104d, and
104e. In this manner the first PWM output signal 214a drives the normal mode switching
elements 104b, 104c, and 104f and the second PWM output signal 214b drives the auxiliary
mode switching elements 104a, 104d, and 104e.
[0041] The PWM channel mixer 212 processes the first and second PWM output
signals 214s, 214b along with a fault command signal 218 generated by the fault detection
module 206. The fault detection signal 218 commands the PWM channel mixer 212 to
selectively output either the first PWM output signal 214a or the second PWM output signal
216b. In this manner, the normal mode or the auxiliary mode of the fault-tolerant magnetic
bearing drive module 100 can be initiated, as discussed in greater detail below.
[0042] To initiate the normal mode of the fault-tolerant magnetic bearing drive
module 100, the positive phase reference current signals (ia_ref, ic_ref,) are sent to the
respective current regulators 208a, 208b. The corresponding duty cycles are also generated
and sent to the respective PWM channel drivers 210a, 210b. The first PWM output signal
214a for driving the normal mode switching elements 104b, 104c, 104f are generated and the
second PWM output signal 214b for driving the auxiliary mode switching elements 104a,
104d, 104e are inhibited (i.e., blocked) from reaching the second PWM channel 216b.
Accordingly, the normal mode of the fault-tolerant magnetic bearing drive module 100 is
initiated. When the fault command signal 218 is generated, negative phase reference currents
(-ia_ref, -ic_ref) are output to the second current regulator 208b. The corresponding duty
cycles are also generated and sent to the second PWM channel driver 210b. The second
PWM output signal 214b for driving the auxiliary mode switching elements 104a, 104d, 104e
are output to the second PWM channel 216, while the first PWM output signal 214a for
driving the normal mode switching elements 104b, 104c, 104f are inhibited from reaching the
first PWM channel 216a. Accordingly, the auxiliary mode of the fault-tolerant magnetic
bearing drive module 100 is initiated.
[0043] The fault detection module 206 is configured to detect one or more electrical
faults of the fault-tolerant magnetic bearing drive module 100 when operating in the normal
mode. According to an embodiment, the fault detection module 206 executes a systematical
fault identification procedure comprising a plurality of identification operations that
determine different in each control cycle. The identification procedure will now be described
with reference to FIG. 4. A first identification operation is configured to detect an overcurrent
protection scenario. For instance, if either of the winding currents IA, Ic exceeds the
over-current limit (I_limitl) at operation 300, a short-circuit fault, for example, is detected
and all the PWM outputs signals (i.e., 214a and 214b) are blocked at operation 302 such that
the whole motor drive system and the magnetic bearing drive 100 are deactivated.
[0044] If the winding currents IA, IC do not exceed the over-current limit (I_limitl) at
operation 300, a second identification operation to detect an external fault is performed at
operation 304. The detection of an external fault is based on a fault signal generated by the
fault- tolerant magnetic bearing drive module 100. If the fault- tolerant magnetic bearing drive
module 100 detects a fault at operation 304, such as a desaturation fault detected by a power
electronic device, the fault-tolerant control is activated and the fault tolerant command signal
commands the PWM channel mixer 212 to disconnect the first PWM output signal 214a and
output the second PWM output signal 214b. For example, a desaturation (DESAT) fault
protection driver configured with over-current DESAT protection can output can be
leveraged with the controller such that the controller can therefore detect the fault without
sensing current and turn-off the switch before failure. In this manner, the normal mode
switching elements 104b, 104c, 104f are deactivated and the auxiliary mode switching
elements 104a, 104d, 104e are activated such that the fault- tolerant magnetic bearing drive
module 100 is switched from the normal mode to the auxiliary mode at operation 306.
[0045] If a fault is not detected at operation 304, a third identification operation is
configured to detect an electrical fault based on a winding current total (i.e., IA+IC) and a
threshold value (I_limit2) at operation 308. When operating in the normal mode, a total (i.e.,
summation) of the first and second winding currents (IA+IC) will be approximately twice the
bias current (i.e., 2xl_bias). As mentioned above, the bias current (I_bias) has been pre
determined. Thus, the threshold value (I_limit2) can be based on a position of the bearing.
That is, I_limit2 can be set, for example, equal to approximately 1.5xl_bias. If IA+IC is less
than the I_limit2 at operation 308, an open-circuit fault is detected and the fault-tolerant
magnetic bearing drive module 100 is switched to the auxiliary mode at operation 310. If all
the three identification steps determine that no fault exists, the fault-tolerant magnetic bearing
drive module 100 continues to operate in normal mode at operation 312.
[0046] Referring to FIG. 4, a signal diagram illustrates operation of a magnetic
bearing fault-tolerant drive system according to a non-limiting embodiment. In this example,
the fault- tolerant magnetic bearing drive module 100 is initially operating in the normal
mode. The Channel 1 signal (Chi) indicates that a position of rotary shaft coupled to a
levitating bearing exists in a centered position. The Channel 2 signal (Ch2) indicates
operation of a central switching element gate signal. The Channel 3 signal (Ch3) and the
Channel 4 signal (Ch4) indicate the first and second winding currents (IA, Ic), respectively,
which are initially in positive phase. At time (tl), Ch2 is cut off due to, for example, an
open-circuit fault, and the first and second winding currents (IA, IC) begin to drop as indicated
by Ch3 and Ch4.
[0047] At approximately t2, the fault detection module 206 detects the fault and
generates the fault-tolerant command signal. The fault tolerant command signal commands
the PWM channel mixer 212 to inhibit the first PWM output signal 214a and output the
second PWM output signal 214b, thereby initiating the auxiliary mode of the fault-tolerant
magnetic bearing drive module 100. Accordingly, the first and second winding currents IA',
Ic' are generated in negative phase within approximately 1 millisecond (ms) from time tl. It
is appreciated that the detection time could also be less than 1 ms. In this manner, levitation
of the bearing can be maintained such that the positional axis of the rotary shaft is kept
centered between two position limits with small transient as indicated by Chi. Therefore, the
magnetic bearing fault-tolerant drive system 200 can effectively detect one or more faults
such as an open-circuit fault, for example, and successfully maintain levitation of the bearing
and axial position of a corresponding rotational shaft. In addition, the magnetic bearing faulttolerant
drive system 200 allows for re-starting the system with the back up working mode. It
is much easier than replacing the hardware and the maintenance cost is reduced.
[0048] While the invention has been described in detail in connection with only a
limited number of embodiments, it should be readily understood that the invention is not
limited to such disclosed embodiments. Rather, the invention can be modified to incorporate
any number of variations, alterations, substitutions or equivalent arrangements not heretofore
described, but which are commensurate with the spirit and scope of the invention.
Additionally, while various embodiments of the invention have been described, it is to be
understood that aspects of the invention may include only some of the described
embodiments. Accordingly, the invention is not to be seen as limited by the foregoing
description, but is only limited by the scope of the appended claims.

CLAIMS:
1. An electronic magnetic bearing fault-tolerant drive module, comprising:
a first plurality of switching elements and a second plurality of switching elements;
and
at least one winding interposed between the first plurality of switching elements and
the second plurality of switching elements, the first and second plurality of switching
elements configured to selectively operate in a first mode and a second mode to generate an
electromagnetic field.
2. The electronic magnetic bearing fault-tolerant drive module of claim 1, further
comprising a diode connected across each switching element among the first and second
plurality of switching elements to form a plurality of bi-directional phase-leg circuits.
3. The electronic magnetic bearing fault-tolerant drive module of claim 2,
wherein the first mode is configured to generate at least one winding current in a first
direction through the at least one winding in response to receiving a first PWM output signal,
and to generate the at least one winding current in a second direction opposite the first
direction through the at least one winding in response to receiving a second PWM output
signal.
4. The electronic magnetic bearing fault-tolerant drive module of claim 3,
wherein a first winding is interposed between a first bi-directional phase-leg circuit and a
second bi-directional phase leg circuit forming a first H-bridge circuit, and a second winding
is interposed between a second bi-directional phase-leg circuit and a third bi-directional phase
leg circuit forming a second H-bridge circuit.
5. The electronic magnetic bearing fault-tolerant drive module of claim 4,
wherein the first H-bridge circuit and the second H-bridge circuit share a single common
phase-leg, and wherein the first H-bridge circuit is configured to control the first winding
current through the first winding and the second H-bridge circuit is configured to control a
second winding current through the second winding, the second winding current controlled to
have an opposite direction with respect to the first winding current.
6. The electronic magnetic bearing fault-tolerant drive module of claim 5,
wherein each bi-directional phase-leg circuit includes a first switching element configured to
conduct current based on the first mode and inhibit current based on the second mode, and a
second switching element configured to inhibit current based on the first mode and conduct
current based on the second mode.
7. An electronic magnetic bearing fault-tolerant drive system comprising:
an electronic magnetic bearing fault-tolerant drive module configured to selectively
operate in a first mode in response to receiving the first PWM output signal and a second
mode in response to receiving the second PWM output signal;
an electronic fault detection module configured to output a fault command signal in
response to detecting an electrical fault of the electronic magnetic bearing fault-tolerant drive
system, the fault command signal initiating transition from the first mode to the second mode.
8. The electronic magnetic bearing fault-tolerant drive system of claim 7, further
comprising an electronic fault-tolerant current controller module configured to selectively
output a first PWM output signal and a second PWM output signal;
9. The electronic magnetic bearing fault-tolerant drive system of claim 8,
wherein in response to receiving the fault command signal, the electronic fault-tolerant
current controller module disconnects the first PWM output signal and outputs the second
PWM output signal to switch the electronic magnetic bearing fault-tolerant drive module
from the first mode to the second mode.
10. The electronic magnetic bearing fault-tolerant drive system of claim 9,
wherein the magnetic bearing fault-tolerant drive module includes at least one winding
configured to generate an electromagnetic field in response to receiving a winding current
flowing in a first direction.
11. The electronic magnetic bearing fault-tolerant drive system of claim 10,
wherein the fault detection module detects an open-circuit fault of the magnetic bearing faulttolerant
drive module based on a comparison between the at least one winding current and a
threshold value.
12. The electronic magnetic bearing fault-tolerant drive system of claim 11,
wherein the electronic magnetic bearing fault-tolerant drive module includes a plurality of b i
directional phase-leg circuits connected to the at least one winding to form at least one Hbridge
circuit.
13. The electronic magnetic bearing fault-tolerant drive system of 12, wherein the
bi-directional phase-leg circuits are configured to generate the winding current in a first
direction in response to receiving the first PWM output signal having a first phase and to
generate the winding current in a second direction opposite the first direction in response to
receiving the second PWM output signal having a second phase opposite the first phase.
14. The electronic magnetic bearing fault-tolerant drive system of 13, wherein the
plurality of bi-directional phase-leg circuits each includes a first switching element
configured to generate current based on the first mode and inhibit current based on the second
mode, and a second switching element configured to inhibit current based on the first mode
and generate current based on the second mode.
15. The electronic magnetic bearing fault-tolerant drive system of 14, wherein the
at least one electrical fault includes an open-circuit fault induced in response to a failure of
the first switching element.