U.S. patent application number 14/620218 was filed with the patent office on 2016-08-18 for method and apparatus for detecting alternator rectifier diode short fault.
The applicant listed for this patent is General Electric Company. Invention is credited to Rajeev VERMA, Bret Dwayne WORDEN.
Application Number | 20160241176 14/620218 |
Document ID | / |
Family ID | 56621482 |
Filed Date | 2016-08-18 |
United States Patent
Application |
20160241176 |
Kind Code |
A1 |
VERMA; Rajeev ; et
al. |
August 18, 2016 |
METHOD AND APPARATUS FOR DETECTING ALTERNATOR RECTIFIER DIODE SHORT
FAULT
Abstract
Methods for detecting a short fault of an alternator rectifier
electronic component include sampling a field winding voltage or
current signal of an alternator, during operation of the
alternator, and determining a fault ripple period at which the
alternator field winding signal exceeds a fault threshold. A short
fault of an electronic component of a rectifier coupled to the
alternator is detected in the event that the fault ripple period
closely matches an alternator armature period. Alternatively or
additionally, the sampled field winding signal is band pass
filtered, and a short fault is detected in the event that an
amplitude of the band pass filtered field winding signal exceeds a
fault threshold. The methods can be implemented, for example, by an
apparatus that includes a hysteresis frequency counter, a frequency
comparator, and a countdown timer.
Inventors: |
VERMA; Rajeev; (Bangalore,
IN) ; WORDEN; Bret Dwayne; (ERIE, PA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
General Electric Company |
Schenectady |
NY |
US |
|
|
Family ID: |
56621482 |
Appl. No.: |
14/620218 |
Filed: |
February 12, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
Y02E 10/72 20130101;
H02P 9/48 20130101; Y02E 10/725 20130101; H02P 9/102 20130101 |
International
Class: |
H02P 9/00 20060101
H02P009/00 |
Claims
1. A method comprising: sampling a field winding signal of an
alternator, during operation of the alternator; determining a fault
ripple period at which the field winding signal exceeds a fault
threshold; and detecting a short fault of an electronic component
of a rectifier coupled to an output of the alternator in the event
that the fault ripple period closely matches an armature period of
the alternator.
2. The method of claim 1 wherein the short fault is detected only
if the fault ripple period closely matches the armature period
throughout a countdown.
3. The method of claim 2 wherein the countdown is at least twenty
times the armature period.
4. The method of claim 2 wherein the countdown is no more than
fifty times the armature period.
5. The method of claim 2 wherein the countdown is at least twenty
times the armature period and no more than fifty times the armature
period.
6. The method of claim 1 wherein the short fault is detected if a
difference between the fault ripple period and the armature period
is no more than 1 Hz.
7. The method of claim 1 wherein the fault threshold is at least
500% of a normal ripple amplitude.
8. The method of claim 1 wherein the fault threshold is at least
10,000% of a normal ripple amplitude.
9. The method of claim 1 wherein the fault ripple period is
determined by obtaining a spectral density of the field winding
signal.
10. A method comprising: sampling a field winding signal of an
alternator, during operation of the alternator; band pass filtering
the field winding signal that is sampled; and detecting a short
fault of an electronic component of a rectifier coupled to an
output of the alternator in the event that an amplitude of the band
pass filtered field winding signal exceeds a fault threshold.
11. The method of claim 10 wherein the band pass filtering is
accomplished by tuning a band pass filter with reference to a
sampled alternator armature frequency.
12. The method of claim 10 wherein the band pass filtering is
accomplished by using a filter set to a design range of values for
an alternator armature frequency.
13. The method of claim 10 wherein the band pass filtering is
accomplished by selecting one of a plurality of band pass filters
based on an operating condition of a prime mover that drives the
alternator.
14. The method of claim 10 wherein the band pass filtering is
accomplished by selecting one of a plurality of band pass filters
based on a rotational speed of the alternator.
15. The method of claim 10 wherein the fault threshold is set based
on an operating condition of a prime mover that drives the
alternator.
16. An apparatus comprising: a hysteresis frequency counter that is
operatively connected to sample a field winding signal of an
alternator and to output a value indicative of a fault ripple
frequency, based on a ripple of the field winding signal exceeding
a fault threshold; a countdown timer; and a frequency comparator
that is operatively connected to compare the fault ripple frequency
to an alternator armature frequency, and to actuate the countdown
timer in the event that the fault ripple frequency closely matches
the armature frequency; wherein the countdown timer is operatively
connected to be actuated by the frequency comparator, and is
configured to signal a short fault of an electronic component of a
rectifier coupled to an output of the alternator in the event that
the fault ripple frequency closely matches the armature frequency
for a countdown time.
17. The apparatus of claim 16 wherein the countdown timer is
configured to signal the short fault if a difference between the
fault ripple frequency and the armature frequency is no more than 1
Hz for the countdown time.
18. The apparatus of claim 16 wherein the fault threshold is at
least 500% of a normal ripple amplitude.
19. The apparatus of claim 16 wherein the fault threshold is at
least 10,000% of a normal ripple amplitude.
20. The apparatus of claim 16 wherein the countdown time is at
least twenty times an armature period of the alternator.
21. The apparatus of claim 16 wherein the countdown time is no more
than fifty times an armature period of the alternator.
22. The apparatus of claim 16 wherein the countdown time is at
least twenty times an armature period of the alternator and no more
than fifty times the armature period.
Description
BACKGROUND
[0001] 1. Technical Field
[0002] Embodiments of the invention relate generally to power
electronics. Other embodiments relate to detecting a shorted diode
or other electronic component in an alternator rectifier.
[0003] 2. Discussion of Art
[0004] Generally, electric vehicles develop tractive effort through
motors fitted to axles or wheel hubs of the vehicles. These motors
receive electrical power from a primary power supply, which may be
an electrochemical battery, an ultracapacitor, a photovoltaic
panel, or a thermochemical engine. If the primary power supply is a
thermochemical engine, it is typical for motion of the engine to
drive an alternator (AC generator), which rotates at a multiple of
the engine cycle rate. In order to provide a clean source of power
regardless of engine speed, the electricity generated in the
alternator is passed through an alternator rectifier, and possibly
additional power electronics, before delivery to the motors.
Nevertheless, rotation of the alternator unavoidably introduces a
small AC ripple to the electrical power delivered from the
alternator rectifier.
[0005] Typically, the alternator rectifier is a solid state device,
although it also can be built from discrete components. In any
case, if a diode of the alternator rectifier fails short (zero
resistance), a large or extremely large AC fault current may flow
down to other power electronics, so that continued operation can
present a risk of secondary damage to the power electronics as well
as to the motors.
[0006] Accordingly, some electric vehicles provide for an emergency
mode of operation of the vehicle in case of an alternator rectifier
diode fault. Also, some electric vehicles automatically enter the
emergency mode in response to detecting an alternator rectifier
diode fault.
[0007] Typically, alternator rectifier diode faults have been
detected on the basis of an abrupt or gradual increase in the
magnitude of AC ripple in the electrical power delivered from the
alternator rectifier. However, to avoid nuisance (false fault)
detections, diode fault detection has been disabled for normal
operation transients such as motor/alternator (regenerative
braking) transition, wheel slip, speed transients, power regulation
mode changes, etc. These customary exclusions from fault detection
produce the predictable problem that there is a possibility of not
detecting an alternator rectifier diode short during normal
operations.
[0008] In view of the above, it may be desirable to provide
apparatus and methods for reliably detecting an alternator
rectifier diode short during any normal operations of an electric
vehicle, including transients for which diode fault detection
previously has been disabled. Such apparatus and methods might also
be helpful toward detecting any alternator rectifier diode short
fault.
BRIEF DESCRIPTION
[0009] In an embodiment, a method (e.g., a method of controlling an
electrical power supply system) includes sampling a field winding
signal (voltage or current) of an alternator, during operation of
the alternator. The alternator is driven by a prime mover to
generate electricity. The method further includes determining a
fault ripple period at which the field winding signal exceeds a
fault threshold, and detecting a short fault in an electronic
component of a rectifier coupled to an output of the alternator in
the event that the fault ripple period closely matches an armature
period of the alternator. "Closely matches" means at or within
(i.e., no more than) a designated threshold.
[0010] For example, the method may include sampling a field winding
voltage of an alternator (during operation of the alternator),
determining a fault ripple period at which the alternator field
winding voltage exceeds a fault threshold, and detecting an
alternator rectifier diode short fault (i.e., a short fault of a
diode of a rectifier operably coupled to the alternator) in the
event that the fault ripple period closely matches an alternator
armature period.
[0011] In another embodiment, a method includes sampling a field
winding signal (voltage or current) of an alternator, during
operation of the alternator. The method further includes band pass
filtering the sampled field winding signal, and detecting a short
fault of an electronic component (e.g., diode) of a rectifier
coupled to an output of the alternator in the event that an
amplitude of the band pass filtered field winding signal exceeds a
fault threshold.
[0012] In another embodiment, an apparatus includes a hysteresis
frequency counter that is operatively connected to sample a field
winding signal (voltage or current) of an alternator, and to output
a value indicative of fault ripple frequency, based on a ripple of
the field winding signal exceeding a fault threshold. The apparatus
further includes a frequency comparator and a countdown timer that
is operatively connected to be actuated by the frequency
comparator. The frequency comparator is operatively connected to
compare the fault ripple frequency to an armature frequency of the
alternator, and to actuate the countdown timer in the event that
the fault ripple frequency closely matches the armature frequency.
The countdown timer is configured to signal a short fault of an
electronic component (e.g., diode) of a rectifier coupled to an
output of the alternator in the event that the fault ripple
frequency closely matches the armature frequency for a countdown
time, e.g., a time that exceeds a design transient duration.
DRAWINGS
[0013] The present invention will be better understood from reading
the following description of non-limiting embodiments, with
reference to the attached drawings wherein below:
[0014] FIG. 1 is a schematic view of an electrical generation
system and a fault detection apparatus, according to an
embodiment.
[0015] FIG. 2 shows graphically an alternator field winding voltage
signal and hysteresis envelope according to an aspect of the
invention.
[0016] FIG. 3 shows schematically an embodiment of a method for
detecting an electrical component short fault (e.g., alternator
rectifier diode short fault).
[0017] FIG. 4 is a schematic view of the fault detector apparatus
of FIG. 1 for implementing the method of FIG. 3, according to an
embodiment of the invention.
DETAILED DESCRIPTION
[0018] Reference will be made below in detail to exemplary
embodiments of the invention, examples of which are illustrated in
the accompanying drawings. Wherever possible, the same reference
characters used throughout the drawings refer to the same or like
parts, without duplicative description. Although exemplary
embodiments of the present invention are described with respect to
electric vehicles, embodiments of the invention also are applicable
for use in alternator-rectifier power systems generally, e.g., as
used with turbine generator sets or other generator sets.
[0019] As used herein, the terms "substantially," "generally," and
"about" indicate conditions within reasonably achievable
manufacturing and assembly tolerances, relative to ideal desired
conditions suitable for achieving the functional purpose of a
component or assembly.
[0020] FIG. 1 shows an electrical power supply system 10 that is
driven by an engine or other prime mover 12 (e.g., diesel engine,
gasoline engine, natural gas engine, multi-fuel engine,
hydro-turbine, wind turbine, steam turbine, etc.). The power supply
system 10 includes an alternator 14, which has a field winding 16
and a stator winding (armature) 18. Although the armature 18 is
shown as a three-phase winding, in other embodiments the armature
is single phase. The alternator is operably coupled to a mechanical
output (e.g., drive shaft) of the prime mover, for being driven by
the prime mover to generate electricity. The power supply system 10
also includes a rectifier 20, inputs of which are connected to an
electric output of the armature 18. The rectifier 20 is configured
to receive electrical power from the alternator at a first power
waveform, and to convert the electrical power to a different power
waveform, which is provided at load terminals 21 of a bus. For
example, the rectifier may be configured to convert an AC power
output of the alternator to DC power available on the bus, e.g.,
voltages +Ve and -Ve are present at the terminals 21, respectively,
when the system is operational. One or more loads 103 are operably
coupled to the terminals 21, e.g., the loads may include one or
more inverters for controllably converting DC power from the bus to
AC signals for powering one or more AC induction motors of an
electric vehicle. The rectifier 20 includes plural diodes 22, any
of which can compromise the functioning of the alternator rectifier
by failing short or open.
[0021] Although embodiments are described herein in relation to
diodes specifically, other embodiments are applicable to electronic
components more generally, which are operably connected in a
circuit of a rectifier to convert one or more voltage inputs (e.g.,
3-phase AC) to one or more voltage outputs (e.g., DC). Examples
include actively-controlled transistors, diode-connected
transistors, and the like.
[0022] The alternator field winding 16 is driven by an exciter 24,
which is connected to receive electrical power from a power source.
For example, the exciter 24 may be powered from the DC load
terminals 21. Alternatively or additionally, the exciter 24 can be
powered from a battery or from another power supply external to the
power supply system 10.
[0023] For detecting a short fault of an alternator rectifier diode
or other electronic component, a fault detector apparatus 100 is
operatively connected to the exciter 24 to sense (or receive
information about) an electrical signal (voltage and/or current) in
the field winding 16. The fault detector apparatus 100 also
receives information 105 about (i) a rotational speed of the
alternator (e.g., from an engine speed sensor) and/or (ii) a stator
(armature) frequency of the alternator, and outputs a signal 101,
indicative of a detected short fault, responsive to certain
conditions being met, as further discussed below. Although the
exciter 24 presumptively supplies DC to the field winding 16, in
fact magnetic back-coupling from the electrical field of the
armature 18 onto the field winding 16 will always superimpose a
small AC ripple voltage ("normal ripple") onto the exciter supply
voltage at approximately the rotational frequency of the armature
18 (e.g., between about 25-87 Hz). In this context, "small" means
on the order of no more than 1 V, e.g., less than 1 V. As mentioned
above, this relatively small normal ripple can cause nuisance
detections (spurious faults) during some normal operating
transients.
[0024] FIG. 2 shows graphically a time progression of a field
winding voltage 200, which includes both a baseline DC voltage 205
as well as either the small normal ripple 210 or an abnormally
large fault ripple 220 that will be coupled into the field winding
16 in the event that one of the alternator rectifier diodes 22
fails. FIG. 2 also shows a hysteresis envelope or fault threshold
230 that is used for distinguishing the fault ripple 220 from the
normal ripple 210. One aspect of the invention involves utilizing
the hysteresis envelope 230 in order to detect the fault ripple 220
and to screen out nuisance detections of the normal ripple 210. In
certain embodiments the hysteresis envelope 230 is set at a large
multiple of the normal ripple amplitude, e.g., at least five times
or 500% of the normal ripple amplitude or at least about 5 V. In
case certain normal operating transients might cause the normal
ripple 210 to exceed 500% of its customary amplitude, then the
fault threshold 230 may be set at a larger multiple, e.g., 1000% or
10,000% of the normal ripple amplitude. However, another mode for
distinguishing the fault ripple 220 from an unusual transient
amplitude of the normal ripple 210 is that normal operating
transients should not exceed a design transient duration 240 as
shown above the fault ripple 220.
[0025] In embodiments, the fault detection apparatus is configured
to receive and assess field winding current signals in a manner
similar to the voltage signals illustrated in FIG. 2. In other
words, the fault detection apparatus may be configured to sense (or
receive information relating to) voltages and/or currents in the
field winding.
[0026] FIG. 3 shows schematically a frequency comparison and
counting method 300 that is implemented by the fault detector
apparatus 100 for detecting a short fault of a rectifier electronic
component (e.g., alternator rectifier diode short fault). According
to the method 300, the apparatus 100 determines 302 a fault ripple
time period 304 at which the field winding signal (voltage or
current) 200 exceeds the fault threshold 230. The apparatus 100
then compares 306 the fault ripple period 304 to an armature
winding period 308. (For example, the armature winding period may
be determined based on the characteristics of the alternator and a
rotational speed of the armature, e.g., provided in information
105.) In the event that the fault ripple period 304 closely matches
the armature winding period 308 (meaning at or within, i.e., no
more than, a designated threshold 310 of the armature winding
period, e.g., at or within a 1 Hz (time equivalent of 1 second) or
about 5% frequency difference), the apparatus 100 triggers a
countdown 312 that is significantly longer than the armature
winding period 308 and also longer than the design transient
duration 240. For example, the countdown 312 may be a specific
multiple of the armature winding period 308, e.g., at least 20
times longer than the armature winding period 308, or in some
applications about 500 msec, so as to allow many confirmation
samples of the fault ripple period 304 for a period well beyond the
design transient duration 240. In certain implementations of the
method 300, the countdown 312 may be limited in duration (e.g., no
more than fifty times longer than the armature winding period 308)
so as to enable an emergency mode of operation before an actual
short fault, or an operating transient that significantly exceeds
the design transient duration 240, can cause significant damage to
other components. In the event that the fault ripple period 304
continues to closely match the armature winding period 308
throughout the countdown 312, then the fault detector apparatus 100
signals 314 a short fault (i.e., outputs the signal 101).
[0027] FIG. 4 is a schematic diagram of an embodiment of the fault
detector apparatus 100, e.g., as configured for implementing the
method 300. Components of the fault detector apparatus 100 include
a field winding signal terminal 102 (e.g., voltage sense terminal)
that is operatively connected to provide a voltage or current
signal received from the alternator field winding 16 to an active
or passive low pass frequency filter 104 and to a ripple subtractor
106. For example, the fault detector 100 may sample the field
winding voltage 200 via the terminal 102 at least once every 2 msec
(0.002 seconds). The low pass filter 104 may have a passband of
0-1.5 Hz for selecting only a DC component of the field winding
signal (e.g., field winding voltage 200). Thus, the low pass filter
104 can be configured to pass through to the subtractor 106 only a
DC amplitude 107 of the field winding signal. Because the terminal
102 also is directly connected to the subtractor 106, the
subtractor 106 is configured to output only the AC ripple 210 or
220 of the field winding voltage or current signal 200.
[0028] The subtractor 106 is operatively connected to supply the AC
ripple 210 or 220 to a hysteresis trigger 108 (e.g., a Schmitt
trigger or similar threshold circuit). The trigger 108 is set
according to the fault threshold 230 as discussed above. Thus, on
receiving a fault ripple 220 that exceeds the fault threshold 230,
the trigger 108 sends a high signal to a fault ripple timer 110.
Otherwise the trigger 108 sends a low signal to the fault ripple
timer 110.
[0029] In response to receiving a low signal from the trigger 108,
the fault ripple timer 110 increments its time value. In response
to receiving a high signal from the trigger 108, the fault ripple
110 outputs its current time value (the fault ripple period 304)
and resets. Together, the frequency filter 104, the ripple
subtractor 106, the trigger 108, and the fault ripple timer 110 are
operable as a hysteresis frequency counter 112 that is operatively
connected to sample the alternator field winding signal (e.g.,
alternator field winding voltage signal 200) and to output a value
(the fault ripple period 304) that is indicative of a fault ripple
frequency, based on the field winding voltage ripple 210 or 220
exceeding the fault threshold 230.
[0030] The frequency counter 112 is operatively connected to send
the fault ripple period 304 to a frequency comparator 114, which
also is operatively connected to receive a value of the armature
winding period 308. For example, the armature winding period 308
may be measured similarly to the fault ripple period 304, may be
obtained from a lookup table, or may be measured differently from
the fault ripple period 304 (e.g., by an optical tachometer). The
frequency comparator 114 is configured and operatively connected to
send a high signal to a countdown timer 116 in the event that the
fault ripple period 304 closely matches the armature winding period
308, e.g., is at or within 1 Hz.
[0031] The countdown timer 116 is operatively connected to receive
a high/low signal from the frequency comparator 114 and is
configured to initiate the countdown 312 after receiving a high
signal, to reset after receiving a low signal, or to trip 314 an
alarm 118 after completing a count.
[0032] Thus, in the event that the fault ripple period 304 closely
matches the armature winding period 308 (e.g., at or within 1 Hz or
about 5%) then the countdown timer 116 initiates the countdown 312
(e.g., a timeout period of 500 msec). In the event that, during the
countdown 312, a new measurement of fault ripple period 304 does
not closely match the armature winding period 308, then the
countdown timer 116 resets. In the event that the fault ripple
period 304 continues to closely match the armature winding period
throughout the countdown 312, then after completing the countdown
312 the countdown timer 116 trips the alarm 118 in order to signal
314 a short fault. Thus, the countdown timer 116 is configured to
signal 314 a short fault in the event that the fault ripple
frequency (inverse of the fault ripple period 304) closely matches
the armature frequency (inverse of the armature winding period 308)
for a time (the countdown 312) that exceeds the design transient
duration 240.
[0033] Some or all of these components can be implemented in
software or in a dedicated circuit, e.g., an ASIC or FPGA or
portion thereof. For example, FIG. 4 shows the frequency comparator
114, countdown timer 116, and alarm 118 all being implemented
within a control module 120. The control module may include a
controller (or processor) and a memory unit, which stores
non-transient instructions that are executed by the controller for
carrying out various operations as set forth herein.
[0034] The various signals (e.g., field winding signal, DC
component of the field winding signal, trigger output) may be
provided to a memory unit, system (e.g., vehicle) controller,
signal bus (for providing the signals to other points in the
apparatus), etc. 109.
[0035] Although FIG. 4 shows one embodiment of a fault detector 100
according to the invention, other embodiments are conceivable. For
example, rather than timing the fault ripple period 304 (counting
the fault ripple frequency) based on the output of the trigger 108,
embodiments of the invention could be implemented by sampling the
alternator field winding voltage 200, band pass filtering the
sampled voltage, and detecting a short fault 316 (e.g., alternator
rectifier diode short fault) in the event that an amplitude of the
band pass filtered field winding voltage exceeds a fault threshold.
The band pass filtering can be accomplished based on the alternator
armature frequency (inverse of the armature winding periodicity
308), for example, by tuning the filter 104 with reference to a
sampled alternator armature frequency or with reference to a design
range of values for alternator armature frequency, or by selecting
the filter 104 from among a plurality of band pass filters based on
an operating condition of the prime mover 12 or based on a
rotational speed of the alternator 14. The fault threshold may be
adjusted or set based on an operating condition of the prime mover
12. As another example, embodiments of the invention could be
implemented by obtaining a running spectral density of the
alternator field winding voltage 200 and identifying whether a
local maximum of the spectral density closely matches the
alternator armature frequency (inverse of the armature winding
period 308) and exceeds the fault threshold 230 for a time that
exceeds the design transient duration 240.
[0036] Thus, embodiments of the invention relate to a method that
includes sampling (e.g., with a fault detection apparatus) a field
winding signal (voltage or current signal) of an alternator, during
operation of the alternator. The method further includes
determining (e.g., with the fault detection apparatus) a fault
ripple period at which the alternator field winding signal exceeds
a fault threshold, and detecting (e.g., with the fault detection
apparatus) a short fault of a diode or other electronic component
of a rectifier (coupled to the alternator) in the event that the
fault ripple period closely matches an alternator armature period.
Some embodiments may detect the short fault only if the fault
ripple period closely matches the alternator armature period
throughout a countdown, e.g., at or within a 1 Hz frequency
difference. The fault threshold may be, e.g., at least 500% of a
normal ripple amplitude, or at least 10,000% of a normal ripple
amplitude. The countdown may be at least twenty times the
alternator armature period, and/or no more than fifty times the
alternator armature period. (Countdowns longer than fifty times the
alternator armature period may be applicable in situations,
depending on the particular characteristics of the alternator and
electrical power generation system, where additional confirmation
samples are deemed useful and/or where a mode of operation that is
triggered within a relatively short time of a possible fault is not
needed. Countdowns shorter than twenty times the alternator
armature period may be applicable in situations, again, depending
on the particular characteristics of the alternator and electrical
power generation system, where relatively fewer confirmation
samples are needed.) The fault ripple period may be determined by
obtaining a spectral density of the field winding voltage.
[0037] Other embodiments implement a method that includes sampling
(e.g., with a fault detection apparatus) a field winding signal
(current or voltage) of an alternator, during operation of the
alternator, and band pass filtering (e.g., with the fault detection
apparatus) the sampled field winding signal. The method further
includes detecting (e.g., with the fault detection apparatus) a
short fault of an electronic component (e.g., diode) of a rectifier
coupled to the alternator in the event that an amplitude of the
band pass filtered field winding signal exceeds a fault threshold.
The band pass filtering may be accomplished by tuning a band pass
filter with reference to a sampled alternator armature frequency,
or by using a filter set to a design range of values for an
alternator armature frequency, or by selecting one of a plurality
of band pass filters based on an operating condition of an engine
that drives the alternator. The band pass filtering may be
accomplished by selecting one of a plurality of band pass filters
based on a rotational speed of the alternator. The fault threshold
may be set based on an operating condition of an engine or other
prime mover that drives the alternator.
[0038] Other embodiments provide an apparatus that includes a
hysteresis frequency counter that is operatively connected to
sample an alternator field winding signal (voltage or current
signal) and to output a value indicative of fault ripple frequency,
based on a ripple of the field winding voltage exceeding a fault
threshold. The apparatus further includes a frequency comparator
and a countdown timer that is operatively connected to be actuated
by the frequency comparator. The frequency comparator is
operatively connected to compare the fault ripple frequency to an
alternator armature frequency, and to actuate the countdown timer
in the event that the fault ripple frequency closely matches the
armature frequency. The countdown timer is configured to signal a
short fault in the event that the fault ripple frequency closely
matches the armature frequency (e.g., at or within a 1 Hz frequency
difference) for a time that exceeds a design transient duration.
The fault threshold may be, e.g., at least 500% of a normal ripple
amplitude or at least 10,000% of a normal ripple amplitude. The
countdown may be at least twenty times the alternator armature
period, and/or no more than fifty times the alternator armature
period.
[0039] In embodiments, the fault detector apparatus is configured,
responsive to detecting a short fault, to one or more of generate a
signal for controlling a device to log information of the fault in
a memory unit, to generate a signal for controlling a device or
system in which the alternator rectifier is disposed (e.g., to
automatically control a vehicle in which the alternator rectifier
is disposed, to bring the vehicle to a designated mode of
operation, to stop the vehicle, to prevent the vehicle when stopped
from moving, to automatically or otherwise control movement of the
vehicle to a designated location, to automatically control a
generator to a de-rated or turned off mode of operation, etc.), to
generate a signal for automatically scheduling maintenance on the
alternator rectifier, and/or otherwise to generate a signal for
communicating information of the fault to another device or system
(e.g., either on-board or off-board a vehicle in which the
alternator rectifier is disposed).
[0040] In an embodiment, a method comprises sampling a field
winding signal of an alternator, during operation of the
alternator. The method further comprises determining a fault ripple
period at which the alternator field winding signal exceeds a fault
threshold. The method further comprises detecting a short fault of
an electronic component of a rectifier coupled to the alternator if
a difference between the fault ripple period and an alternator
armature period is no more than a designated threshold (e.g., no
more than the designated threshold throughout a countdown
time).
[0041] In another embodiment, an apparatus comprises a hysteresis
frequency counter, a countdown timer, and a frequency comparator.
The hysteresis frequency counter is operatively connected to sample
a field winding signal of an alternator and to output a value
indicative of a fault ripple frequency, based on a ripple of the
field winding voltage exceeding a fault threshold. The frequency
comparator is operatively connected to compare the fault ripple
frequency to an alternator armature frequency, and to actuate the
countdown timer in the event that a difference between the fault
ripple frequency and the armature frequency is no more than a
designated threshold. The countdown timer is operatively connected
to be actuated by the frequency comparator, and is configured to
signal a short fault of an electronic component of a rectifier
coupled to the alternator in the event that the difference (between
the fault ripple frequency and the armature frequency) is no more
than the designated threshold for a countdown time.
[0042] In another embodiment, an apparatus comprises a hysteresis
frequency comparator that is configured to: sample a field winding
signal of an alternator, during operation of the alternator;
determine a fault ripple period at which the alternator field
winding signal exceeds a fault threshold; and detect a short fault
of an electronic component of a rectifier coupled to the alternator
in the event that the fault ripple period closely matches an
alternator armature period.
[0043] In another embodiment, an apparatus comprises a hysteresis
frequency comparator that is configured to: sample a field winding
signal of an alternator, during operation of the alternator; band
pass filter the field winding signal that is sampled; and detect a
short fault of an electronic component of a rectifier coupled to
the alternator in the event that an amplitude of the band pass
filtered field winding voltage exceeds a fault threshold.
[0044] In another embodiment, an electrical power supply system
includes a prime mover, an alternator that is coupled for being
driven by the prime mover to generate electricity, a rectifier
coupled to an output of the alternator and configured to convert a
first power signal that is output by the alternator to a different,
second power signal, one or more loads coupled to receive the
second power signal, and a fault detection apparatus coupled to
receive information about the alternator in operation. The
rectifier includes plural diodes and/or other electronic
components. The fault detection apparatus is configured to sample a
field winding signal of the alternator, during operation of the
alternator. The fault detection apparatus is further configured to
determine a fault ripple period at which the field winding signal
exceeds a fault threshold, and to detect a short fault of one of
the electronic components of the rectifier in the event that the
fault ripple period closely matches an armature period of the
alternator. Responsive to detecting the short fault, the fault
apparatus is configured to generate a signal to control the
electrical power supply system, a device in which the electrical
power supply system is disposed (e.g., a vehicle), or some other
device.
[0045] In another embodiment, an electrical power supply system
includes a prime mover, an alternator that is coupled for being
driven by the prime mover to generate electricity, a rectifier
coupled to an output of the alternator and configured to convert a
first power signal that is output by the alternator to a different,
second power signal, one or more loads coupled to receive the
second power signal, and a fault detection apparatus coupled to
receive information about the alternator in operation. The
rectifier includes plural diodes and/or other electronic
components. The fault detection apparatus is configured to sample a
field winding signal of the alternator, during operation of the
alternator. The fault detection apparatus is further configured to
band pass filter the field winding signal that is sampled, and to
detect a short fault of one of the electronic components of the
rectifier in the event that an amplitude of the band pass filtered
field winding signal exceeds a fault threshold. Responsive to
detecting the short fault, the fault apparatus is configured to
generate a signal to control the electrical power supply system, a
device in which the electrical power supply system is disposed
(e.g., a vehicle), or some other device.
[0046] In another embodiment, an electrical power supply system
includes a prime mover, an alternator that is coupled for being
driven by the prime mover to generate electricity, a rectifier
coupled to an output of the alternator and configured to convert a
first power signal that is output by the alternator to a different,
second power signal, one or more loads coupled to receive the
second power signal, and a fault detection apparatus coupled to
receive information about the alternator in operation. The
rectifier includes plural diodes and/or other electronic
components. The fault detection apparatus includes a hysteresis
frequency counter that is operatively connected to sample a field
winding signal of the alternator and to output a value indicative
of a fault ripple frequency, based on a ripple of the field winding
signal exceeding a fault threshold. The fault detection apparatus
further includes a frequency comparator and a countdown timer that
is operatively connected to be actuated by the frequency
comparator. The frequency comparator is operatively connected to
compare the fault ripple frequency to an alternator armature
frequency, and to actuate the countdown timer in the event that the
fault ripple frequency closely matches the armature frequency. The
countdown timer is configured to generate a signal indicative of a
short fault of one of the electronic components of the rectifier in
the event that the fault ripple frequency closely matches the
armature frequency for a countdown time. The electrical power
supply system may be configured for the signal to be routed to
control the electrical power supply system, a device in which the
electrical power supply system is disposed (e.g., a vehicle), or
some other device.
[0047] In another embodiment, a vehicle includes an embodiment of
the aforementioned electrical power supply system, one or more
inverters coupled as one or more of the loads, and one or more
traction motors (motors used to propel a vehicle) connected to
receive electrical power from the inverters. The signal generated
responsive to detecting a short fault is routed to control the
electrical power supply system and/or movement of the vehicle.
[0048] It is to be understood that the above description is
intended to be illustrative, and not restrictive. For example, the
above-described embodiments (and/or aspects thereof) may be used in
combination with each other. In addition, many modifications may be
made to adapt a particular situation or material to the teachings
of the invention without departing from its scope. While the
dimensions and types of materials described herein are intended to
define the parameters of the invention, they are by no means
limiting and are exemplary embodiments. Many other embodiments will
be apparent to those of skill in the art upon reviewing the above
description. The scope of the invention should, therefore, be
determined with reference to the appended claims, along with the
full scope of equivalents to which such claims are entitled. In the
appended claims, the terms "including" and "in which" are used as
the plain-English equivalents of the respective terms "comprising"
and "wherein." Moreover, in the following claims, terms such as
"first," "second," "third," "upper," "lower," "bottom," "top," etc.
are used merely as labels, and are not intended to impose numerical
or positional requirements on their objects. Further, the
limitations of the following claims are not written in
means-plus-function format and are not intended to be interpreted
based on 35 U.S.C. .sctn.112, sixth paragraph, unless and until
such claim limitations expressly use the phrase "means for"
followed by a statement of function void of further structure.
[0049] This written description uses examples to disclose several
embodiments of the invention, including the best mode, and also to
enable one of ordinary skill in the art to practice embodiments of
the invention, including making and using any devices or systems
and performing any incorporated methods. The patentable scope of
the invention is defined by the claims, and may include other
examples that occur to one of ordinary skill in the art. Such other
examples are intended to be within the scope of the claims if they
have structural elements that do not differ from the literal
language of the claims, or if they include equivalent structural
elements with insubstantial differences from the literal language
of the claims.
[0050] As used herein, an element or step recited in the singular
and proceeded with the word "a" or "an" should be understood as not
excluding plural of the elements or steps, unless such exclusion is
explicitly stated. Furthermore, references to "one embodiment" of
the present invention are not intended to be interpreted as
excluding the existence of additional embodiments that also
incorporate the recited features. Moreover, unless explicitly
stated to the contrary, embodiments "comprising," "including," or
"having" an element or a plurality of elements having a particular
property may include additional such elements not having that
property.
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