Breaker/starter with auto-configurable trip unit

A combination circuit breaker/motor starter includes a circuit breaker trip unit having a microprocessor and at least one removably connectable contactor or other functional module. The functional module is encoded with an identifier, such that the microprocessor can determine the type of functional module and appropriate configuration parameters, such as trip times, for the particular application of the functional module. Power is supplied continuously to the trip unit during motor overload or short circuit conditions.

CROSS REFERENCE TO RELATED APPLICATION
 This is related to U.S. patent application Ser. No. 09/375,694 entitled
 Small-Sized Industrial Rated Electric Motor Starter Switch Unit filed
 concurrently herewith which is incorporated herein by reference.
 BACKGROUND OF THE INVENTION
 The present invention relates to an integrated circuit breaker/starter for
 a motor.
 In the field of motor control, it is known to control the operation of a
 motor (e.g., to start or stop the motor) using a contactor, which is a
 three pole switch which is electrically operated by a (usually)
 continuously energized solenoid operating coil. It is also known to
 provide thermal protection, i.e., overload protection, to a motor against
 overload conditions using a motor overload relay. Overload conditions
 occur when equipment is operated in an electrically undamaged circuit in
 excess of normal full-load rating, or when conductors carry current in
 excess of rated ampacity. Overload conditions persisting for a sufficient
 length of time will damage or overheat the equipment. Overload conditions
 do not include faults which require instantaneous protection such as a
 short circuit or ground fault or a loss of a phase. The terms "overload,"
 "overload protection" and "overload relay" are defined in the National
 Electrical Manufacturers Association (NEMA) standard ICS2, which is herein
 incorporated by reference. Typical overload relays have been implemented
 using bimetal relays, and more recently using electronics and current
 transformer sensors. A conventional motor starter is typically implemented
 by a combination of a contactor and a motor overload relay.
 Overload conditions result in a cumulative heating effect in motor
 circuits, and subsequently a cooling effect after the motor circuit is
 deenergized, such as with an overload relay. Therefore, the length of time
 that a motor can operate before overheating under overload conditions will
 vary if the motor is energized and deenergized too frequently. This
 cumulative heating and cooling effect is known as thermal memory, i.e.,
 operating memory as defined in NEMA standard ICS2.
 Typical overload relays, such as bimetal relays, compensate for thermal
 memory of the motor mechanically through the thermal memory of the bimetal
 components within the relays themselves. However, thermal memory, i.e.,
 the cumulative heating and cooling effect, changes between motor
 applications. Therefore, a bimetal relay must be matched to a particular
 motor and cannot be used to provide overload protection for more than one
 motor application.
 Electronic devices, e.g., electronic overload relays or electronic trip
 units, can compensate for thermal memory through software algorithms. The
 algorithms have adjustable parameters that can be changed from one motor
 application to another. However, unlike the bimetal relays, the ability to
 compensate for thermal memory is lost in prior art electronic devices when
 power is interrupted.
 To protect an electrical motor from electrical overload conditions, it is
 known to use a circuit breaker in combination with a motor starter. Motor
 control centers and combination starter panels both use motor combination
 starters. There are typically two types of circuit breakers used in motor
 starter applications. The first is an "inverse time" general circuit
 breaker, and the second (more common) type is the "instantaneous trip"
 only circuit breaker, which provide instantaneous protection from faults
 such as short circuits, ground faults or a loss of a phase. The
 instantaneous trip circuit breaker is more typically used in motor
 applications due to cost considerations, and because the use of an inverse
 time circuit breaker provides more protection than is typically needed.
 Further, inverse time circuit breakers are not typically configured for
 motor protection, as motor protection requires different trip times than
 typical circuit breaker applications.
 A typical motor application circuit is shown in FIG. 1. The circuit is
 connected between lines L1 and L2 and includes a normally-closed stop
 switch 10, a normally-open start switch 12, a contactor coil 14, and a
 conventional overload relay 15. The contactor coil 14 is energized or
 de-energized appropriately to operate contactors in a three-phase system,
 where each of three phase lines A, B, and C has a circuit breaker 16a,
 16b, and 16c, respectively, contactors 14a, 14b, and 14c, respectively,
 and motor overload protection 18a, 18b, and 18c, respectively. The circuit
 breakers 16a, 16b, and 16c are typically implemented by instantaneous trip
 circuit breakers.
 It would be desirable to consolidate the circuit breaker instantaneous trip
 with a motor starter overload protection. It would also be desirable to be
 able to vary or reconfigure the circuit breaker trip time for different
 motor applications. It would further be desirable to prevent the circuit
 breaker from tripping during a motor overload condition and to be able to
 provide a substantially continuous power supply to the motor electronics
 so that the occurrence of an overload condition and thermal memory can be
 remembered.
 SUMMARY OF THE INVENTION
 The present invention overcomes the problems described above, and achieves
 additional advantages, by providing for an integrated circuit
 breaker/motor starter which includes a controller or contactor arranged to
 control an electrical motor, and a motor overload relay/trip unit for
 providing thermal protection for the electrical motor, the overload relay
 being connected to the controller or contactor and being capable of
 receiving at least one removably connectable contactor module. The
 contactor module can be a circuit breaker, and can be encoded such that
 the connection of the module will provide an indication to the controller
 of desired trip time configuration. Thus, numerous module types can be
 readily connected or disconnected from the starter to adapt the integrated
 starter/breaker to a variety of motor control applications.

DETAILED DESCRIPTION
 Referring now to FIG. 2, a known circuit breaker for use with the
 integrated breaker/starter of the present invention is shown. It should be
 appreciated that the circuit shown in FIG. 2 is a single line diagram of
 the circuit breaker shown and described in U.S. Pat. No. 4,589,052. In the
 circuit breaker of FIG. 2, conductor 20 is sensed by means of current
 transformer CT which provides a current value which is rectified within
 rectifier 22. A voltage value indicative of the composite current is
 developed across a burden resistor Rb which is inputted to the integrated
 circuit trip unit 24 by means of negative bus 26. A power supply 28
 connecting between ground and the positive bus 30 receives its operating
 power from the same current transformers. When a trip output signal is
 generated within trip unit 24 a control signal is sent over line 32 to a
 driver circuit 34 for gating an SCR 36 which allows operating current to
 flow through the flux-shift trip coil 38 thereby tripping the circuit
 breakers 40. The integrated circuit trip unit or "chip" 24 is a 40-pin
 very large scale integration (VLSI) implementation. A plurality of digital
 switches (not shown) can be used for setting the various interrupting
 levels and time delays as well as the various options available within the
 chip 24. The interrupting levels can include the adjustable current
 setting, which varies the level of current the breaker will carry
 indefinitely without tripping, the long time (LT) overcurrent "pickup"
 value, the short time (ST) pickup value, ground fault pickup value and
 instantaneous pickup value. It should be appreciated that numerous other
 details of the operation are disclosed in U.S. Pat. No. 4,589,052, the
 entirety of which is incorporated by reference.
 Referring now to FIG. 3, a block diagram of a removably connectable
 contactor module according to an embodiment of the present invention is
 shown. The contactor module 50 is connected between terminals 52 and 54,
 and includes a voltage protection and rectification module 56, a control
 power supply module 58, and an over/under voltage module 60, each of which
 is connected to each of the others via a bidirectional link. The contactor
 module further includes a coil energizing module 62 which is connected
 between the power supply module 58 and the over/under voltage module 60,
 and the module 62 receives input from each of the module 58 and 60 over
 unidirectional links as shown. The contactor module further includes a
 coil-deenergizing module 64 which is connected by two conductors 65 to the
 coil energizing module 62. A contactor coil 14 is connected between the
 conductors 65. The coil energizing module controls the energizing of the
 coil 14, and the coil de-energizing module controls the de-energizing of
 the coil 66. The coil energizing module 62 includes an oscillator, a
 current level comparator, an energizing signal generator, and a single
 shot generator. While these elements are not explicitly shown in FIG. 3,
 they are generally well-known in the art.
 Referring now to FIG. 4, a block diagram of an integrated breaker/starter
 according to an embodiment of the present invention is shown. In this
 embodiment, the power supplies (28, 58) and operating systems (of the trip
 unit and of the module) are isolated. In this embodiment, the integrated
 breaker/starter includes a circuit breaker portion 70, which is
 substantially similar to the circuit breaker shown and described with
 respect to FIG. 2, and an add on contactor module portion 72, which is
 substantially similar to the module embodiment shown and described with
 respect to FIG. 3, with the exception that the power supply 58 and
 over/under voltage module 60 of the module of FIG. 3 have been omitted for
 ease of illustration. It should be appreciated that the module 72
 substantially replaces the coil 14 and conventional overload relay 15 of
 FIG. 1. The portions 70 and 72 are connected by an opto-isolator 76 and
 isolation transformer 78. The voltage protection and rectification module
 56 is connected between the start switch 12, located on a first line L1,
 and an output line L2. Lines L1 and L2 are connected to an incoming
 control voltage, fed from a control power transformer (CPT) or alternative
 power source, at a voltage which is typically 120 volts but can range up
 to approximately 600 volts. It should be noted that a conductor 11
 converts line L1 directly to the voltage protection/rectification module
 56, such that the module 56 receives a voltage supply after the stop
 switch 10 is operated. The contactor coil 66 is energized or de-energized
 as appropriate to operate the contactors 14.
 In operation, the current through the line 20 connected to the motor is
 sensed by current transformer CT, is rectified by rectifier 22, and the
 rectified output (a DC voltage) is provided to trip unit 24. The detected
 voltage (i.e., the rectified output) is compared (e.g., in a comparator
 associated with the trip unit) to a predetermined threshold to determined
 whether a short circuit, motor overload, or other predetermined condition
 has occurred. In the event of a short circuit condition, the trip unit
 acts in a conventional manner (e.g., as described with respect to FIG. 2)
 to provide a trip signal through driver 34, SCR 36, and trip coil 38 to
 cause the circuit breaker to trip. When the contactor module 72 is turned
 on, a pulse width modulator (PWM; not shown) is turned on for a time
 period determined by a single shot timer (not shown). This causes an
 energizing control signal to be provided to the coil energizing module 62
 through the opto-isolator to energize the coil 66 at an initial inrush
 current level. Upon the expiration of the time period set by the single
 shot timer, the energizing current is reduced to a holding current level
 which keeps the circuit sealed. In response to the detection of an
 overload condition (based on the output of the comparison described
 above), the pulse width modulator is turned off, and the coil 66 is
 de-energized. It should be appreciated that if the circuit breaker 40 is
 tripped, the power will be removed from the control electronics, and that
 during a motor overload condition, the circuit breaker will not trip. In
 both situations, the power supply 28 supplies power to the control
 electronics substantially without interruption via L1 and L2, and voltage
 protection/rectification module 56, so that the electronics can remember
 that a motor overload condition occurred even when power is interrupted.
 Therefore the overload protection can provide thermal memory. By not
 tripping the circuit breaker during a motor overload condition, the
 present invention can advantageously and effectively provide both motor
 overload and short circuit protection in an integrated circuit
 breaker/motor starter.
 Referring now to FIG. 5, a block diagram of an alternative embodiment of
 the present invention is shown, in which the power supplies and operating
 systems are not isolated. In this embodiment, the coil energizing module
 24/62, in addition to having the functions of the coil energizing module
 62 of FIG. 4, is further provided with the functions of the circuit
 breaker/overload trip unit 24 of FIG. 4. Thus, in the module 24/62 of FIG.
 5, there is provided a full circuit breaker trip unit, an internal
 overload trip means for controlling the contactor coil, and a coil
 energizing system including a current level comparator, oscillator,
 energizing signal generator, and a single shot generator.
 An alternative arrangement is shown in FIG. 6, and can be implemented by
 replacing module 24/62 with a microprocessor based combination motor
 starter module 63 having a trip unit and a coil control unit. The trip
 unit 63 in this alternative embodiment preferably has two independent
 outputs to breaker and contactor for instantaneous trip (via elements 34,
 36, and 38) and overload trip (via a driver 35 and a pulse width modulator
 module 37 connected between the power supply 28 and the coil and
 de-energizing modules 66, respectively). The trip unit 63 also preferably
 includes phase loss protection and an external power supply to provide
 thermal memory for proper overload protection. The coil control portion
 preferably performs full contactor coil control (i.e., over/under
 voltage), an oscillator, a current level comparator, an energizing signal
 generator, and a single shot generator.
 Still another alternative arrangement is shown in FIG. 7. In this
 alternative, an integrated breaker/starter scheme without isolation is
 shown, with a relay scheme, including multiple coils 66a, 66b, multiple
 SCRs 65a, 65b, relay coil 67 and relay 69 substantially replacing the PWM
 module and de-energizing module 37 of FIG. 6. The microprocessor-based
 combination starter module 63 is substantially the same as in FIG. 6.
 Referring to FIGS. 4 & 5, it will be appreciated that the electronic trip
 unit 24 contained in the main circuit breaker unit initiates the operation
 of both the circuit breaker 40 and the contactor 14, but that operation of
 the contactor 14 is performed by the add-on module 72. Thus, the trip unit
 24 must be approximately configured to initiate operation of the contactor
 14 according to the desired application. Referring now to FIG. 8, a
 simplified block diagram of a first exemplary connection scheme for the
 trip unit module 70 and an add-on module 14. In the embodiment of FIG. 8,
 the trip unit module 70 includes an A/D converter 80 which connects with
 the add-on module 72. One suitable A/D converter is described in U.S. Pat.
 No. 4,589,052. The A/D converter converts a coded signal provided by the
 add-on module 72 to a digital output identification signal, and provides
 this output signal to microprocessor 82 (contained within the circuit
 breaker trip unit). The microprocessor 82 receives the digitized
 identification signal from the A/D converter, and performs a configuration
 sequence and automatic configuration routine and determines the
 appropriate trip time for the circuit breaker and other circuit
 parameters. In this matter, the trip point can be automatically
 reconfigured for a wide variety of applications.
 Referring now to FIG. 9 a simplified block diagram of a second exemplary
 connection scheme for the trip unit module 70 and add-on module 72. In the
 embodiment of FIG. 9, the A/D converter of FIG. 8 has been replaced by a
 plurality of connections directly between the add-on module 72 and the
 trip unit module 70. It should be appreciated that the connection scheme
 of FIG. 8 accommodates a relatively large number of possible connection
 combinations, but can add to the complexity and cost of the trip unit if
 there is no spare analog/digital converter associated with the
 microprocessor. In contrast, the connection scheme of FIG. 9 is relatively
 simpler and cheaper, but requires the use of multiple microprocessor
 input/output lines.
 It should be appreciated that while the invention has been described using
 a removably connectable contactor module, the present invention can
 accommodate any of number of removably connectable modules, connected as
 shown and described with respect to FIGS. 8-9. In each case, the
 connectable modules are encoded or identified such that when the module is
 connected to the trip unit module, the microprocessor associated with the
 trip unit module can determine the appropriate trip times, contactor coil
 pickup and hold current, and other parameters which are specific to a
 particular application.
 FIG. 10 is a flow chart describing the steps for providing circuit breaker
 and motor starter protection according to one embodiment of the present
 invention. In step 100, a suitably programmed microprocessor associated
 with a circuit breaker determines that a removably connectable module has
 been connected to the circuit breaker unit. In step 102, the
 microprocessor determines (e.g., from identification coding contained in
 the removably connectable module) the type of connectable module and/or
 appropriate configuration parameters (e.g., circuit breaker trip time,
 contactor coil closing time, contactor coil pickup and hold current, etc.)
 for the particular connectable module. In step 104, the microprocessor
 runs an automatic configuration routine based on the information
 determined in step 102 to automatically configure the trip times and other
 configuration parameters. In step 106, the circuit breaker monitors motor
 current to determine whether a predetermined condition (e.g., a short
 circuit condition or a motor overload condition) has occurred. If a
 predetermined condition occurs, the microprocessor automatically initiates
 the appropriate remedial action. For a short circuit condition, the
 microprocessor will output a control signal to cause the circuit breaker
 to trip, and for a motor overload condition (assuming the connectable
 module is a contactor module), the microprocessor will output a control
 signal to cause the contactor coil to be de-energized to open the
 contactor. For a different application, the connectable module can be
 removed and replaced with a different module, and the microprocessor will
 automatically reconfigure the parameters for the new application.
 FIG. 11 is a flow chart describing the steps for providing circuit breaker
 and motor starter protection according to another embodiment of the
 present invention. In step 110, a suitably programmed microprocessor
 associated with a circuit breaker determines that a removably connectable
 module has been connected to the circuit breaker unit. In step 112, the
 microprocessor determines (e.g., from identification coding contained in
 the removably connectable module) the type of connectable module and/or
 appropriate configuration parameters (e.g., circuit breaker trip time,
 contactor coil closing time, contactor coil pickup and hold current, etc.)
 for the particular connectable module. In step 114, the microprocessor
 runs an automatic configuration routine based on the information
 determined in step 112 to automatically configure the trip times and other
 configuration parameters. In step 116, the circuit breaker monitors motor
 current to determine whether a predetermined condition (e.g., a short
 circuit condition or a motor overload condition) has occurred. In step
 118, the microprocessor provides a trip signal to breaker as a system
 backup in event of an overload trip via a contactor malfunction. This
 backup overload breaker trip function sets up the electronic trip unit to
 provide backup overload protection. This backup function trips the breaker
 in the event the overload trip fails and the breaker still detects that an
 overload current is still flowing. At a specific point later in the cycle,
 this fault system allows sufficient time for the primary trip means to
 react. This fault function is configured within the programming of the
 microprocessor to provide the backup overload trip function. If a
 predetermined condition occurs, the microprocessor automatically initiates
 the appropriate remedial action. For a short circuit condition, the
 microprocessor will output a control signal to cause the circuit breaker
 to trip, and for a motor overload condition (assuming the connectable
 module is a contactor module), the microprocessor will output a control
 signal to cause the contactor coil to be de-energized to open the
 contactor.
 Referring now to FIGS. 12 and 13, trip time curves of a standard inverse
 time breaker configuration, and a motor configuration are shown. As will
 be apparent from FIG. 13, the motor overload trip times according to
 embodiments of the present invention are selectable between e.g., class
 10, class 20, and class 30.
 While the exemplary embodiments have been described assuming a contactor
 add-on module, it should be emphasized that the invention offers a major
 benefit by accommodating many types of modules for many types of motor
 applications. In addition to National Electrical Manufacturer's
 Association (NEMA) or International Electro-Technical Commission (IEC)
 contactor modules, fused limiter modules (which respond to high short
 circuit, high current applications), enhanced trip unit modules (a higher
 level trip unit with metering functions), ground fault protection modules,
 and communication modules (for communicating motor information to a remote
 processor). The simple "plug and play" aspect of the present invention
 assures reliable operation and avoids use mistakes by automatically
 reconfiguring breaker/starter parameters for specific applications.
 While the foregoing description includes numerous specific details, these
 details are for purposes of explanation only, and are not intended to
 limit the scope of the invention. The details and embodiments described
 above can be varied in many ways without departing from the spirit and
 scope of the invention, as defined by the following claims and their legal
 equivalents.