U.S. patent application number 14/541786 was filed with the patent office on 2016-05-19 for contact wear detection by spectral analysis shift.
The applicant listed for this patent is SCHNEIDER ELECTRIC USA, INC.. Invention is credited to Gerald B. CARSON, John B. McCONNAUGHEY, Barry N. RODGERS, Craig S. WALLACE, II.
Application Number | 20160139206 14/541786 |
Document ID | / |
Family ID | 54544956 |
Filed Date | 2016-05-19 |
United States Patent
Application |
20160139206 |
Kind Code |
A1 |
CARSON; Gerald B. ; et
al. |
May 19, 2016 |
CONTACT WEAR DETECTION BY SPECTRAL ANALYSIS SHIFT
Abstract
A contact wear detector includes an electrical contact 100
having a base layer 110 composed of a first material and a
contacting layer 120 composed of a second material, to electrically
contact an opposing contact in the circuit. The base layer is
capable of having portions exposed through worn areas 125 of the
contacting layer. The first material of the base layer is
configured to form an arc 210 between the portions of the base
layer exposed through the worn areas and the opposing contact when
the contacts separate. The arc thus formed emits light 212 having a
characteristic optical spectrum of the first material. An optical
detector 220 is proximate to the electrical contacts, to detect the
characteristic optical spectrum of the light emitted by the arc
between the portions of the base layer exposed through the worn
areas and the opposing contact.
Inventors: |
CARSON; Gerald B.; (Raleigh,
NC) ; WALLACE, II; Craig S.; (Whitakers, NC) ;
McCONNAUGHEY; John B.; (Raleigh, NC) ; RODGERS; Barry
N.; (Raleigh, NC) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SCHNEIDER ELECTRIC USA, INC. |
Palatine |
IL |
US |
|
|
Family ID: |
54544956 |
Appl. No.: |
14/541786 |
Filed: |
November 14, 2014 |
Current U.S.
Class: |
324/415 |
Current CPC
Class: |
G01R 31/3272 20130101;
G01R 31/333 20130101; H01H 1/02372 20130101; H01H 33/66 20130101;
G01R 31/327 20130101; H01H 1/0015 20130101; H03K 17/18 20130101;
H02H 3/04 20130101; G01R 31/3274 20130101; H01H 2001/0026
20130101 |
International
Class: |
G01R 31/327 20060101
G01R031/327 |
Claims
1. A contact wear detector, comprising: an electrical contact
having a base layer composed of a first material and a contacting
layer composed of a second material, the contacting layer being
configured to electrically contact an opposing contact in a switch,
the base layer being capable of having portions exposed through
worn areas of the contacting layer, the first material of the base
layer being configured to form an arc between the portions of the
base layer exposed through the worn areas and the opposing contact
when the contacts separate, the arc thus formed emitting light
having a characteristic optical spectrum of the first material; and
an optical detector proximate to the electrical contact, the
optical detector being configured to detect the characteristic
optical spectrum of the light emitted by the arc between the
portions of the base layer exposed through the worn areas and the
opposing contact.
2. The contact wear detector, of claim 1, wherein the first
material of the base layer is brass and the second material of the
contact layer is zinc.
3. The contact wear detector, of claim 1, wherein the electrical
contact is a component of a switch comprising one of a contactor, a
circuit breaker, and a relay.
4. The contact wear detector, of claim 1, wherein both the
electrical contact and the optical detector are components of a
single package.
5. The contact wear detector, of claim 1, wherein both the first
material of the base layer and the second material of the
contacting layer contribute to forming an arc with the opposing
contact when the contacts separate, the arc thus formed emitting
light having characteristic optical spectra of both the first
material and the second material; and the optical detector
proximate to the electrical contact being configured to detect the
characteristic optical spectra of both the first material and the
second material.
6. The contact wear detector, of claim 5, wherein contact wear is
detected by an increase in spectrum intensity emitted from the
first material of the base layer.
7. The contact wear detector, of claim 5, wherein contact wear is
detected by a decrease in spectrum intensity emitted from the
second material of the contacting layer.
8. The contact wear detector, of claim 1, wherein the first
material of the base layer is composed of multiple materials that
have mutually distinctive optical spectra, so that there is a
gradual change in composition of the first material being eroded by
arc erosion.
9. The contact wear detector, of claim 1, wherein the second
material of the contacting layer is composed of multiple materials
that have mutually distinctive optical spectra, so that there is a
gradual change in composition of the second material being eroded
by arc erosion.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The invention disclosed relates wear detection in electrical
contacts.
[0003] 2. Discussion of the Related Art
[0004] The switching of electrical currents produces arcing between
switch contacts, having the potential to cause considerable damage
to the contacts. Metal atoms are eroded and ionized from the
contact, resulting in arc erosion. Arc erosion on the contacts of a
switch impair good contact joint integrity when the switch is fully
closed.
[0005] Contact wear detection is needed to indicate whether switch
contacts need replacement. Often, the contacts are either replaced
too early or too late in the life cycle, merely on an external
schedule or after a set number of operations. Earlier attempts to
detect contact wear focused a source of ultraviolet light on a
fluorescent trace material previously applied to an electrical
contact. The amount of optical fluorescence detected from the
UV-illuminated trace material, was related to the amount of wear of
the contacts.
SUMMARY OF THE INVENTION
[0006] In accordance with an example embodiment of the invention, a
contact wear detector in a switch includes an electrical contact
having a base layer composed of a first material and a contacting
layer composed of a second material. Either one or both of the
switch contacts may have a base layer of the first material that is
coated with a contacting layer of the second material.
[0007] Each time the contacts open, an arc occurs, wherein the
presently exposed surface of the contact is locally heated, causing
evaporation of some of the material of the exposed surface, which
is ionized forming a plasma between the separating contacts.
[0008] Ions of the evaporated material composing the arc, emit
light having the characteristic optical spectrum of the material of
the exposed surface.
[0009] The characteristic optical spectrum of the light emitted
from the arc, is detected and analyzed by an optical detector in
the switch and connected electronics.
[0010] For new switch contacts, only the second material coating is
presently exposed and the arc plasma is composed primarily of
second material ions that emit the characteristic optical spectrum
of second material, which is detected and recognized by the optical
detector and connected electronics.
[0011] As time goes on, the second material coating is eroded,
causing the formation of worn areas in the second material coating,
which expose the underlying first material.
[0012] When the contacts open and an arc occurs, the presently
exposed surface of the first material in the worn areas, is locally
heated, causing evaporation of some of the first material, which is
ionized forming the plasma between the separating contacts.
[0013] The ions of the evaporated first material composing the arc,
emit light having the characteristic optical spectrum of first
material.
[0014] The characteristic optical spectrum of first material, in
the light emitted from the arc, is detected and analyzed by the
optical detector in the switch and connected electronics,
indicating the worn condition of the contacts.
[0015] In example embodiments, the first material in the base layer
may be brass and the second material in the contacting layer may be
zinc. In other example embodiments, the first material may be
brass, copper, nickel, or aluminum and the second material may be
silver, tin, gold, or tungsten carbide. The electrical contact may
be a component of a contactor, a circuit breaker, or a relay, as
well as a switch.
[0016] The invention enables simpler maintenance scheduling,
provides early detection of excessive contact wear, promotes
extended life of electrical contacts, and eliminates the need to
disassemble complex equipment to determine the contact status of
component switches.
DESCRIPTION OF THE FIGURES
[0017] Example embodiments of the invention are depicted in the
accompanying drawings that are briefly described as follows:
[0018] FIG. 1A shows an electrical contact having a base layer
composed of a first material and a contacting layer composed of a
second material, the contacting layer being configured to
electrically contact an opposing contact in a switch.
[0019] FIG. 1B shows the electrical contact of FIG. 1A, wherein the
contacting layer has become worn in areas as a result of arc
erosion, the base having portions exposed through the worn areas of
the contacting layer. The figure further shows the first material
of the base layer forming an arc between the portions of the base
layer exposed through the worn areas and the opposing contact when
the contacts separate. The figure further shows the arc thus formed
emitting light having a gradually increasing component from the
first material, which is detected by an optical detector proximate
to the contacts.
[0020] FIG. 2 shows the light emitted from the arc formed between
the contact of FIG. 1B and an opposing contact of a switch, when
the contacts separate. The light is shown being detected by the
optical detector proximate to the contracts. The optical detector
and associated electronics detect the characteristic optical
spectrum of the light emitted by the arc between the portions of
the base layer exposed through the worn areas and the opposing
contact.
[0021] FIG. 3 shows an example of a single package, such as a
circuit breaker, with the optical detector located proximate to the
switch contacts of FIG. 2, the optical detector configured to
detect the light emitted from the arc formed between the contacts
when they separate. The optical detector and the associated
electronics of FIG. 2, detect the characteristic optical spectrum
of the light emitted by the arc, thereby detecting an amount of
wear of the contacts.
[0022] FIG. 4A shows an example spectral image of brass, indicating
a large peak in the irradiance at a wavelength of 520 nm for
brass.
[0023] FIG. 4B shows an example spectral image of zinc, indicating
there is no peak in the irradiance at 520 nm for zinc.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
[0024] FIG. 1A shows an electrical contact 100 having a base layer
composed of a first material, such as brass, and a contacting layer
120 composed of a second material, such as zinc. The contacting
layer 120 may be configured to electrically contact an opposing
contact 100' in a switch 205 shown in FIG. 2.
[0025] Each time the contacts 100 and 100' open, an arc 210 occurs,
as shown in FIG. 1B. The presently exposed surface of the contact
100 is locally heated, causing evaporation of some of the material
of the exposed surface, which is ionized forming a plasma between
the separating contacts 100 and 100'. Ions of the evaporated
material composing the arc 210, emit light 212 shown in FIG. 1B,
the light 212 having the characteristic optical spectrum of the
material of the exposed surface of the contact 100. The
characteristic optical spectrum of the light emitted from the arc
210, may be detected by an optical detector 220 shown in FIG. 1B
proximate to the contacts and analyzed by connected electronics
230, 240, and 250 shown in FIG. 2.
[0026] For new switch contacts 100 and 100', only the second
material, such as zinc, in the contacting layer 120, is presently
exposed. The plasma of the arc 210 is composed primarily of second
material, (e.g., zinc) ions that emit the characteristic optical
spectrum of the second material, (e.g., zinc). The characteristic
optical spectrum of the second material, (e.g., zinc). is detected
and recognized by the optical detector 220 and connected
electronics 230, 240, and 250.
[0027] As time goes on, the second material of the contacting layer
120 is eroded by arc erosion, causing the formation of worn areas
125 in the second material coating, which expose the underlying
first material of the base layer 110, as shown in FIG. 1B. As the
contacts wear, there may be a transition period during which both
the first material of the base layer 110 and the second material of
the contacting layer 120 are eroding and may contribute to the arc
210. When both materials are contributing to the arc, the light 212
will be emitted from both materials. The appearance of the optical
spectrum of the first material of the base layer 110 may be gradual
as the contacting layer 120 is worn away.
[0028] In alternate embodiments, the first material of the base
layer 110 and/or the second material of the contacting layer 120
may be composed of multiple materials that have mutually
distinctive optical spectra, so that there may be a gradual change
in the composition of the material being eroded by arc erosion.
Correspondingly, there is a gradual change in the optical spectrum
of the light emitted by the arc as the contacting layer 120 is worn
away.
[0029] FIG. 1B shows the electrical contact 100 of FIG. 1A, wherein
the contacting layer 120 has become worn in areas 125 as a result
of arc erosion, so that the base layer 110 may have portions
exposed through the worn areas 125 of the contacting layer 120.
[0030] When the contacts 100 and 100' open and the arc 210 occurs,
the presently exposed surface of the base layer 110 of the first
material, such as brass, in the worn areas 125, is locally heated,
causing evaporation of some of the first material (e.g., brass),
which is ionized forming the plasma between the separating contacts
100 and 100'. The ions of the evaporated first material (e.g.,
brass) composing the arc 210, emit light 212 having the
characteristic optical spectrum of first material (e.g.,
brass).
[0031] FIG. 1B shows the optical detector located proximate to the
contact 100. The characteristic optical spectrum of first material
(e.g., brass), in the light 212 emitted from the arc 210, is
detected by the optical detector 220 in the single package, i.e.
packaging, 200 of the switch 205 and analyzed by the connected
electronics 230, 240, and 250 shown in FIG. 2, indicating the worn
condition of the contacts.
[0032] As discussed above, as the contacts wear, there may be a
transition period during which both the first material of the base
layer 110 and the second material of the contacting layer 120 may
be involved in the arc 210, and the light 212 will be emitted from
both materials. The optical detector 220 and connected electronics
may discriminate between the spectra for the first and second
materials. The optical detector 220 and connected electronics may
detect an increase in the spectrum intensity emitted from the first
material of the base layer 110, as an indication of contact wear In
other embodiments of the invention, the optical detector 220 and
connected electronics may detect a decrease in the spectrum
intensity emitted from the second material of the contacting layer
120, as an indication of contact wear.
[0033] FIG. 2 shows the light 212 emitted from the arc 210 formed
between the contact 100 of FIG. 1B and the opposing contact 100' of
the switch 205, when the contacts 100 and 100' separate. The light
200 is shown being detected by the optical detector 220 in the
single package 200, for example a circuit breaker, which also
contains the switch 205. The optical detector 220 and associated
electronics 230, 240, and 250 detect the characteristic optical
spectrum of the light 212 emitted by the arc 210 between the
portions of the base layer 110 exposed through the worn areas 125
and the opposing contact 100'.
[0034] The optical detector 220 may be located proximate to the
contacts 100 and 100' on the inside of the single package 200 and
the associated electronics 230, 240, and 250 may be connected to
the optical detector 220 and located on the outside or remotely of
the single package 200.
[0035] The associated electronics may include scaling and
digitizing circuitry 230, signal processing and decision circuitry
(analog or digital) 240, and communication and human-machine
interface (HMI) components for indication 250.
[0036] The optical detector 220 may be a cadmium sulfide photocell
that is tuned to detect the light 212 having the characteristic
optical spectrum of first material (e.g., brass) of the base layer
110. Adjustment and tuning circuitry 225 may be connected to the
optical detector 220 to fine-tune the sensitivity of the light
sensor/optical detector 220. For example, a cadmium sulfide optical
detector 220 may be tuned to detect the 520 nm irradiance peak of
brass in the base layer 110.
[0037] In example embodiments, the first material in the base layer
110 may be brass and the second material in the contacting layer
120 may be zinc. In other example embodiments, the first material
in the base layer 110 may be copper, nickel, or aluminum and the
second material in the contacting layer 120 may be silver, tin,
gold, or tungsten carbide. The electrical contact 100 may be a
component of any switch including but not limited to a contactor, a
circuit breaker, or a relay.
[0038] FIG. 3 shows a circuit breaker as an example of the single
package 200, with the optical detector 220 located proximate to the
switch contacts 100 and 100' of FIG. 2. The optical detector 220 is
configured to detect the light 212 emitted from the arc 210 formed
between the contacts 100 and 100' when they separate. The
associated electronics of FIG. 2 may be connected to the optical
detector 220 and located outside the circuit breaker. The optical
detector 220 detects the characteristic optical spectrum of the
light 212 emitted by the arc 210, thereby detecting an amount of
wear of the contacts 100 and 100' of the circuit breaker.
[0039] The example circuit breaker is shown in the ON state 40 with
the operating handle 4 in an ON position. The figure shows the
operating handle 4 pivotally mounted on a pivot 10 to the inside of
the case 3. The operating handle 4 is operatively coupled to a
contact operating mechanism 20 in the case 3, to open the contacts
100 and 100' when the user moves the operating handle 4 toward the
ON position. The figure shows a cam 19 of the operating handle 4
being operatively coupled to a current-responsive tripping
mechanism 22 in the case 3, to open the contacts 100 and 100' in
response to a current-responsive tripping mechanism 22 having
detected an over-current in the circuit breaker. The optical
detector 220 is positioned in the case 3, proximate to the contacts
100 and 100', to detect the light 212 emitted from the arc 210
formed between the contacts 100 and 100', when they are separated
either by manual actuation of the operating handle or in response
to the current-responsive tripping mechanism.
[0040] Two common materials used in making contacts are brass and
zinc. FIG. 4A shows an example spectral image of brass and FIG. 4B
shows an example spectral image of zinc. Comparing the spectra of
these two materials shows a large peak in the irradiance at a
wavelength of 520 nm for brass, which is not present in the
irradiance for zinc. Thus, brass as the base layer 110 and zinc as
the contacting layer 120 may be used to indicate the wear of the
contacts 100 and 100'. If the contact 100 were coated with zinc,
the 520 nm peak in irradiance would only appear after the zinc wore
through.
[0041] The invention enables simpler maintenance scheduling,
provides early detection of excessive contact wear, promotes
extended life of electrical contacts, and eliminates the need to
disassemble complex equipment to determine the contact status of
component switches.
[0042] Although specific example embodiments of the invention have
been disclosed, persons of skill in the art will appreciate that
changes may be made to the details described for the specific
example embodiments, without departing from the spirit and the
scope of the invention.
* * * * *