APPARATUS FOR INDICATING A STATUS OF AN APPARATUS THAT
ENERGIZES A PROTECTIVE DEVICE, AND ASSOCIATED METHOD
BACKGROUND
Field
The disclosed and claimed concept relates generally to an apparatus that is
configured to energize a protective device to open at least a portion of a circuit and.
more particularly, to an apparatus that performs a predetermined action when its
ability to initiate the opening of the circuit has dropped to a predetermined threshold.
Description of the Related Art
Numerous types of circuit interrupters are known. One type of circuit
interrupter is in the form of a relay that includes an current measurement circuit that
employs various algorithms to determine when to disconnect the power to a large
load, such as a motor, in certain predefined overload scenarios. Such circuit
interrupters may include an energy storage device such as an electrolytic capacitor to
energize a solenoid of a relay which causes another solenoid to change state to cause a
contactor to interrupt the circuit. While such circuit interrupters have generally been
effective for their intended purposes, such circuit interrupters have not been without
limitation.
As is generally understood, the energy storage capability of an electrolytic
capacitor can degrade over time, and elevated temperatures can accelerate such
degradation. Depending upon the degree of degradation, such a capacitor may store
an insufficient amount of energy to energize the solenoid that initiates the opening of
the circuit. Moreover, while certain overload conditions can occur in an extremely
short period of time, other overload conditions develop over several minutes or even
hours, and it is generally undesirable for equipment to suddenly stop operating.
whether because the power supply to the equipment has been interrupted or because
the equipment has overheated or otherwise failed. It thus would be desirable to
address these and other shortcomings known in the relevant art.
SUMMARY
Accordingly, an improved apparatus in the form of an overload relay includes
a number of current transformers that draw power from a circuit it protects in order to

evaluate the circuit and also to power itself. The current transformers charge a
capacitor which powers a processor and which can energize a solenoid to toggle a
normally CLOSED set of contacts to an OPEN condition to cause another solenoid to
open a contactor to interrupt the circuit to a load. Advantageously, the overload relay
further includes a capacitor analysis circuit which detects one or more operational
parameters of the capacitor and enables a processor of the overload relay to determine
when the energy storage capability of the capacitor has dropped to a predetermined
threshold. In the event of such a determination, the overload relay can perform any of
a number of predetermined actions, such as sending an indication that the overload
relay or the capacitor itself should be replaced in a given period of time or by causing
the capacitor to energize the solenoid to interrupt the circuit. The overload relay
further advantageously includes a visual indicator that includes an LED that is able to
provide a visual indication of a status of the overload relay.
Accordingly, an aspect of the disclosed and claimed concept is to provide an
improved overload relay that is self-powered and that includes a visual indicator that
provides an indication of a status of the overload relay.
Another aspect of the disclosed and claimed concept is to provide an improved
overload relay that is configured to protect a circuit and that provides an indication of
its potential inability to protect the circuit.
These and other aspects of the disclosed and claimed concept are provided by
an improved apparatus that is structured to at least initiate an opening of at least a
portion of a circuit. The general nature of the apparatus can be stated as including a
number of current transformers structured to draw current from the circuit to energize
the apparatus, a housing, a processor disposed on the housing and powered by the
number of current transformers, and a visual indicator connected with the processor
and structured to provide a number of visual indications representative of a status of
the apparatus, at least a portion of the visual indicator being powered by the number
of current transformers.
Other aspects of the disclosed and claimed concept are provided by an
improved method of indicating a status of an apparatus that is structured to at least
initiate an opening of at least a portion of a circuit. The apparatus includes a number
of current transformers structured to draw current from the circuit to energize the

apparatus, a housing, a processor disposed on the housing and powered by the number
of current transformers, and a visual indicator connected with the processor. The
general nature of the method can be stated as including powering at least a portion of
the visual indicator with the number of current transformers, and providing a number
of visual indications representative of a status of the apparatus.
BRIEF DESCRIPTION OF THE DRAWINGS
A further understanding of the disclosed and claimed concept can be
understood from the Description when read in conjunction with the accompanying
drawings in which:
Fig. 1 is a schematic depiction of an improved overload relay and a circuit that
it protects;
Fig. 2 is a flowchart depicting certain aspects of the improved overload relay
of Fig. 1; and
Fig. 3 is another flowchart depicting other aspects of the improved overload
relay of Fig. 1.
Similar numerals refer to similar parts throughout the specification.
DESCRIPTION
An improved overload relay 4 in accordance with the disclosed and claimed
concept is depicted schematically in Fig. 1. The overload relay 4 monitors and
controls a circuit that comprises three phases 8A, 8B, and 8C, collectively referred to
hereinafter with the numeral 8, that extend between a power source 12 and a load 16
which, in the depicted exemplary embodiment, is an electric motor. The circuit also
includes a main disconnect 20 that can be manually operated as well as a contactor
apparatus 24 that is operated by the overload relay 4 to interrupt the circuit.
The overload relay 4 comprises a housing 26 upon which are disposed three
current transformers 28A, 28B, and 28C, collectively referred to hereinafter with the
numeral 28, which are used to monitor the current through the phases 8 and to power
at least a portion of the overload relay 4. In powering the overload relay, the current
that is drawn from the phases 8 by the current transformers 28 is delivered to a boost
regulator 32 and then to a storage device which, in the exemplary embodiment herein.
is in the form of an electrolytic capacitor 36. Current drawn from the phases 8 by the

current transformers 28 is stored in the capacitor 36 which, in turn, powers various
functions of the overload relay 4.
The current transformers 28 are additionally connected with a current
measurement circuit 40 that is connected with a processor 44. The current
measurement circuit 40 enables the processor 44 to monitor the current in the phases 8
and to take action in certain predetermined circumstances. The processor 44 has
numerous algorithms incorporated thereon to evaluate the amount of current flowing
through the phases 8 as a function of time and it is configured to interrupt the circuit
when needed. For instance, the processor 44 might employ an algorithm whereby
current is monitored over time as an indication of the temperature of the motor. If the
current flowing through the circuit is at a sufficient level for a sufficient period of
time, the processor 44 might determine that the load 16 is in danger of overheating
and will determine that the circuit should be interrupted, by way of example.
Advantageously, the overload relay 4 further comprises a capacitor analysis
circuit 48 which serves as a detection system to detect certain operational parameters
of the capacitor 36, such as its voltage. While Fig. 1 schematically depicts the
capacitor analysis circuit 48 as being interposed electrically between the capacitor 36
and the processor 44, it is understood that other connection arrangements can be
employed without departing from the present concept. The operation of the capacitor
analysis circuit 48 will be discussed in greater detail elsewhere herein.
The overload relay 4 further comprises a protective device in the form of a
solenoid 52 which is of a latching type. In certain predefined circumstances, the
processor 44 can cause the solenoid 52 to be energized by the capacitor 36 to toggle a
set of normally CLOSED contacts 56 to an OPEN condition and to toggle a set of
normally OPEN contacts 60 to a CLOSED condition. Since the solenoid 52 is of a
latching type, a pulse of energy from the capacitor 36 causes the solenoid 52 to
change states and thus to toggle the normally CLOSED contacts 56 and the normally
OPEN contacts 60 to their OPEN and CLOSED alternate conditions, respectively,
regardless of whether the energy from the capacitor 36 ceases. That is, another pulse
of energy or a mechanical reset is required to cause the solenoid 52 to return to its
original, i.e., normal condition and to toggle the normally CLOSED contacts 56 and

the normally OPEN contacts 60 to their CLOSED and OPEN normal conditions,
respectively.
When the solenoid 52 is energized and toggles the normally OPEN contacts 60
to their CLOSED condition, an indicator 64 is energized, and the indicator 64 can be
in the form of a light, an alarm, etc. When the normally CLOSED contacts 56 are
toggled by the solenoid 52 to their OPEN condition, it interrupts an operating current
that had been flowing through the normally CLOSED contacts 56 to a solenoid 68 of
the contactor apparatus 24, and such interruption of the operating current causes the
solenoid 68 to change state and to operate the contactor, which interrupts the circuit to
the load 16. The solenoid 68 is of a non-latching type, such that the interruption of
operating current to the solenoid 68 due to the normally CLOSED contacts 56 being
toggled to their OPEN condition causes the solenoid 68 to change states and interrupt
the circuit.
The overload relay 4 further advantageously comprises an indictor which, in
the exemplary embodiment depicted herein, is a visual indicator 72 that comprises an
illumination source and a secondary, mechanical indicator. It is understood, however,
that the visual indicator 72 could alternately or additionally include an audible
indicator component without departing from the present concept. The illumination
source is the exemplary embodiment depicted herein is an LED 76 that is powered by
the capacitor 36 from current drawn from the circuit by the current transformers 28.
The secondary indicator is in the form of an exemplary mechanical reset 80 which
physically moves when the solenoid 52 changes state. That is. when the solenoid 52
is in a first state, the mechanical reset 80 is in a first physical position, as is depicted
schematically in solid lines in Fig. 1. However, if the solenoid 52 is energized by the
capacitor 36 and is caused to change state to a second state, the mechanical reset 80
physically moves to another position, as is indicated in dashed lines at the numeral 82.
which can be visually ascertained by a technician.
The overload relay 4 further comprises a communications interface 84 and a
user interface 88 connected with the processor 44 that enable interaction with the
overload relay 4. For instance, the communications interface 84 can be used to
communicate signals to a remote device such as a sensor or a computer device, by
way of example. The user interface 88 can be used to connect with a remote

computer device or other apparatus to enable a technician to interact with the overload
relay 4 to operate the overload relay 4 or to receive data from the overload relay 4. or
both, by way of example.
Advantageously, the LED 76 can provide visual indications of any of a
plurality of statuses of the overload relay 4. For instance, since the LED 76 is self-
powered, i.e., is powered by current drawn by the current transformers 28 from the
phases 8 of the circuit, the LED 76 will be in an unilluminated condition, i.e., will be
dark, during the initial charging of the capacitor 36. That is, the LED 76 will be
unilluminated when the capacitor 36 has stored therein insufficient energy to energize
the solenoid 52, which is one status of the overload relay 4.
Once the capacitor 36 has reached a desirable level of charge and has stored
therein enough energy to reliably energize the solenoid 52, the LED 76 is caused to
blink in a first predetermined fashion. For instance, the LED 76 can be caused to
blink one time per second, by way of example, to indicate that the capacitor 36 is
charged and that the overload relay 4 is functioning properly. This is another status of
the overload relay 4.
Depending upon the output from the current measurement circuit 40. the
processor 44 may cause the LED to blink in a second, predetermined fashion if a trip
condition is imminent but has not yet occurred. By way of example, the LED 76 can
be caused to blink twice per second, which would indicate still another status of the
overload relay 4.
In the event that the capacitor 36 is caused by the processor 44 to energize the
solenoid 52 and interrupt the circuit, the LED 76 likely will again be unilluminated
since current is not flowing through the phases 8 and the capacitor 36 will have been
substantially discharged from its energizing of the solenoid 52. However, since the
mechanical reset 80 will move to its second position, as is indicated at the numeral 82
the second position of the mechanical reset 80 in combination with the LED 76 being
in an unilluminated condition will indicate yet another status of the overload relay. In
this regard, it is understood that an unilluminated condition of the LED 76 in
combination with the mechanical reset 80 being in its first position (as is indicated at
the numeral 80 in Fig. 1) is what typically will serve as the indication that the status of
the overload relay 4 is that of being in an initial charging condition with the capacitor

36 being less than fully charged. It is also understood that the various statuses of the
overload relay 4 can be communicated to another device via the communications
interface 84.
Further advantageously, the capacitor analysis circuit 48 is operable to
determine the energy storage capability of the capacitor 36 in order to generate an
alarm or perform some type of predetermined action when the energy storage
capability has dropped to a predetermined threshold. The predetermined threshold
typically will be just above the amount of energy required to energize the solenoid 52.
That is, the predetermined action is performed if the capacitor 36 reaches a condition
where its ability to energize the solenoid 52 is potentially questionable.
The capacitor analysis circuit 48 can evaluate the energy storage capability of
the capacitor 36 in any of a variety of fashions. For instance, the capacitor analysis
circuit 48 may partially discharge the capacitor 36 and detect the voltage at one or
more times during the at least partial discharging process. By way of further example.
the capacitor analysis circuit 48 may cause the capacitor 36 to be charged at an energy
storage level greater than that to which it is typically charged and may evaluate the
degree to which the capacitor 36 maintains the extra charge by evaluating the voltage
of the capacitor 36 as a function of time. Numerous other methodologies can be
envisioned, such as those wherein evaluation of the capacitor 36 occurs without
directly monitoring any of the characteristics of the capacitor 36. Rather, such an
evaluation of the capacitor 36 could involve the evaluation of other factors such as the
duration of time during which the capacitor 36 has been in service, the ambient
temperature over time, the number of charge/discharge cycles of the capacitor 36. etc..
by way of example.
Advantageously, if the capacitor 36 is determined to have an energy storage
capability that has dropped to a predetermined threshold, the processor 44 can trigger
a visual alarm, an audible alarm, or both, and/or can communicate a signal over the
communications interface 84 to another device. Additionally or alternatively, the
processor 44 can trigger the capacitor 36 to energize the solenoid 52 and interrupt the
circuit. Furthermore, the LED 76 can be triggered to blink or be otherwise
illuminated in still another fashion, such as to blink three times per second, by way of
example. Other predetermined actions can be envisioned.

It is understood that the processor 44 or the capacitor analysis circuit 48 or
both can be involved in the determination that the energy storage capability of the
capacitor 36 has dropped to the predetermined threshold. It is also understood that
other criteria can be employed in determining whether the capacitor 36 or the
overload relay 4 itself should be replaced.
The predetermined action that is taken by the overload relay 4 in response to a
determination that the energy storage capability of the capacitor 36 has dropped to a
predetermined threshold can be interpreted in any of a variety of fashions. By way of
example, the visual or audible alarm may indicate the need to replace the capacitor 36
or the overload relay 4 within ninety days or at the next scheduled maintenance cycle.
Alternatively, the communications interface 84 may be employed to communicate to
another device a message representative of a warning that the capacitor 36 or the
overload relay 4 itself should be replaced within ninety days. Further advantageously,
the processor 44 can receive input from the current measurement circuit 40 to provide
a further indication that the capacitor 36 or the overload relay 4 itself should be
replaced immediately. In such a scenario, the initial warning of replacement in ninety
days may have been initially provided, but the temperature conditions of the load 16.
and thus potentially the ambient conditions, may have been determined by the current
measurement circuit 40 to be such that a more immediate replacement of the capacitor
36 or the overload relay 4 itself may be required.
The LED 76 is disposed on the housing 26 but can alternatively be disposed
elsewhere or can be in the form of a plurality of LEDs disposed in various locations
on and remote from the housing 26. Thus, a technician looking at the overload relay
4, and thus the housing 26, can advantageously ascertain a status of the overload relay
4.
An improved method of operating the overload relay 4 is depicted generally in
Fig. 2. Energy is stored, as at 104, in a storage device such as the capacitor 36. An
analysis operation is performed, as at 108, on the capacitor 36, with one or more
operational parameters of the capacitor 36 being detected, as at 112. If. as at 116. it is
determined that the energy storage capability of the capacitor 36 has dropped to a
predetermined threshold, a predetermined action is performed, as at 120. As
mentioned elsewhere herein, examples of such a predetermined action would include

any one or more of the triggering of a visual alarm, the triggering of an audible alarm,
the communicating of a signal over a communications interface to another device, and
the energizing of a protective device such as the solenoid 52. Other predetermined
actions will be apparent.
Another flowchart depicting other advantageous features of the overload relay
4 is depicted generally in Fig. 3. A visual indicator such as would include the LED 76
is self-powered, as at 204, such as by employing the current transformers 28 to draw
current from the circuit that is being protected by the overload relay 4. At least a first
visual indication is provided, as at 208, that is representative of a status of the
overload relay 4. As mentioned elsewhere herein, the LED 76 can blink in any of a
variety of fashions or can be unilluminated. When the LED 76 is unilluminated, the
condition of the mechanical reset 80 can be used to determine whether the overload
relay 4 is in an initial charging condition or whether it has already tripped. It is
understood that the visual indications can be supplemented by further
communications provided to an external device via the communications interface 84.
While specific embodiments of the invention have been described in detail, it
will be appreciated by those skilled in the art that various modifications and
alternatives to those details could be developed in light of the overall teachings of the
disclosure. Accordingly, the particular arrangements disclosed are meant to be
illustrative only and not limiting as to the scope of invention which is to be given the
full breadth of the claims appended and any and all equivalents thereof.

4. Overload relay (apparatus)
8ABC Phases (circuit)
12. Power Source
16. Load (motor)
20. Main Disconnect
24. Contactor apparatus
26. Housing
28ABC CTs
32. Boost Regulator
36. Storage Device (capacitor, stores energy)
40. Current Measurement Circuit
44. Processor
48. Capacitor Analysis Circuit (detection system, detects operational parameter
voltage)
52. Solenoid (overload relay, protective device, latching type)
56. Normally Closed Contacts (toggles)
60. Normally Open Contacts
64. Indicator
68. Solenoid (contactor apparatus, non-latching type)
72. Visual Indicator (could be and/or audible)
76. Illumination Source (LED)
80. Secondary Indicator (mechanical reset)
84. Communications Interface
88. User Interface

we claim:
1. An apparatus (4) structured to at least initiate an opening of at least a portion of a
circuit, the apparatus comprising:
a number of current transformers (28A, 28B. 28C) structured to draw current from the
circuit to energize the apparatus;
a housing (26);
a processor (44) disposed on the housing and powered by the number of current
transformers; and
a visual indicator (72) connected with the processor and structured to provide a number
of visual indications representative of a status of the apparatus, at least a portion of the visual
indicator being powered by the number of current transformers
the visual indicator comprising an illumination source (76) that is structured to blink in a
first predetermined fashion to indicate a first status of the apparatus and to blink in a second
predetermined fashion to indicate a second, different status of the apparatus.
2. The apparatus of Claim 1 wherein the apparatus that is structured to at least
initiate an opening of at least a portion of a circuit is an overload relay.
3. The apparatus of Claim 2 wherein the illumination source is an LED.
4. The apparatus of Claim 1 wherein the illumination source is structured to be
unilluminated to indicate at least one of a third status of the apparatus and a fourth status of the
apparatus.
5. The apparatus of Claim 4 wherein the visual indicator further comprises a
secondary indicator (80) that is movable between one position and another position, wherein the
secondary indicator in the one position in combination with the unilluminated condition of the
illumination source is indicative of the third status of the apparatus, and wherein the secondary
indicator in the another position in combination with the unilluminated condition of the
illumination source is indicative of the fourth status of the apparatus.
6. The apparatus of Claim 1 wherein the illumination source is disposed on the
housing.
7. A method of indicating a status of an apparatus (4) that is structured to at least
initiate an opening of at least a portion of a circuit, the apparatus including a number of current

transformers (28A, 28B, 28C) structured to draw current from the circuit to energize the
apparatus, a housing (26), a processor (44) disposed on the housing and powered by the number
of current transformers, and a visual indicator (72) that comprises an illumination source (76)
and that is connected with the processor, the method comprising:
powering at least a portion of the visual indicator with the number of current
transformers;
providing a number of visual indications representative of a status of the apparatus; and
at least one of:
blinking in a first predetermined fashion to indicate a first status of the apparatus.
and
blinking in a second predetermined fashion to indicate a second, different status
of the apparatus.
8. The method of Claim 7, further comprising:
blinking in a first predetermined fashion by blinking a predetermined number of times
per second; and
blinking in a second predetermined fashion by blinking another predetermined number of
times per second.
9. The method of Claim 7, wherein the illumination source comprises an LED. and
further comprising causing the LED to be unilluminated to indicate at least one of a third status
of the apparatus and a fourth status of the apparatus.
10. The method of Claim 9 wherein the visual indicator further comprises a secondary
indicator (80) that is movable between one position and another position, and further comprising
at least one of:
indicating the third status of the apparatus with the secondary indicator in the one
position in combination with the unilluminated condition of the illumination source, and
indicating the fourth status of the apparatus with the secondary indicator in the another
position in combination with the unilluminated condition of the illumination source.
11. An apparatus (4) structured to at least initiate an opening of at least a portion of a
circuit, the apparatus comprising:
a number of current transformers (28A. 28B. 28C) structured to draw current from the
circuit to energize the apparatus;

a housing (26);
a processor (44) disposed on the housing and powered by the number of current
transformers; and
a visual indicator (72) connected with the processor and structured to provide a number
of visual indications representative of a status of the apparatus, the visual indicator comprises an
illumination source (76) and a secondary indicator (80), at least a portion of the visual indicator
being powered by the number of current transformers; and
the secondary indicator being movable between one position and another position, the
secondary indicator in the one position in combination with the illumination source being in an
unilluminated condition being indicative of one status of the apparatus, and the secondary
indicator in the another position in combination with the illumination source being in an
unilluminated condition being indicative of another status of the apparatus.
12. The apparatus of Claim 11 wherein the illumination source is structured to be in
an illuminated condition to indicate either of a pair of different statuses of the apparatus.
13. The apparatus of Claim 12 wherein the illumination source in the illuminated
condition is structured to blink in a first predetermined fashion to indicate one different status of
the apparatus and to blink in a second predetermined fashion to indicate another different status
of the apparatus.
14. The apparatus of Claim 11 wherein the illumination source is disposed on the
housing.
15. The apparatus of Claim 11 wherein the apparatus that is structured to at least
initiate an opening of at least a portion of a circuit is an overload relay.

An improved overload relay includes a number of current transformers that
draw power from a circuit it protects in order to evaluate the circuit and also to power
itself. The overload relay advantageously includes a visual indicator that includes an
LED that is able to provide a visual indication of a status of the overload relay.