Claims:
1. A safe torque off system for an alternating current motor wherein the system enables safe torque off (STO) using any or a combination of a software control and a hardware control.
2. The system of claim 1, wherein the system provides the software control using a digital logic module and the hardware control using a driver supply regulator.
3. The system of claim 2, wherein the digital logic module further provide for redundancy of signals to trigger the STO.
4. The system of claim 2, wherein various safe categories of the STO are implemented using same hardware.
5. The system of claim 2, wherein the system decelerates the alternating current motor slowly to stop upon triggering of the STO.
6. The system of claim 2, wherein the system further provides a Human Machine Interface for implementing the STO.
7. The system of claim 2, wherein notification of an STO command is provided to the digital logic module.
, Description:FIELD OF DISCLOSURE

[0001] The present disclosure relates to electrical motors. In particular, it pertains to a system for controlling alternating current motors.

BACKGROUND OF THE DISCLOSURE

[0002] The background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
[0003] Alternating Current (AC) motors (interchangeably termed as motor hereafter) working on principle of induction are very widely used in industrial applications since they are rugged, reliable and economical. Although traditionally used in fixed-speed service, such motors are increasingly being used as variable-frequency drives (VFDs) in variable-speed service. VFDs offer especially important energy savings opportunities for AC motors in variable-torque loads such as centrifugal fans, pumps and compressors.
[0004] A variable-frequency drive (VFD) (also termed adjustable-frequency drive, variable speed drive, AC drive, micro drive or inverter drive) controls an AC motor’s speed and torque by varying motor input frequency and voltage. Typically it has three main sub-systems: AC motor, main drive controller assembly (VFD Controller) and drive/operator interface. Many times, the motor and the VFD are considered as separate assemblies although strictly the VFD should include the motor as well.
[0005] The VFD controller is a solid-state power electronics conversion system consisting of three distinct sub-systems: a rectifier bridge converter, a direct current (DC) link, and an inverter. Voltage-source inverter (VSI) is by far the most common type of inverter. Most drives are AC-AC drives in that they convert AC line input to AC inverter output. However, in some applications such as common DC bus or solar applications, drives are configured as DC-AC drives. The most basic rectifier converter for the VSI drive is configured as a three-phase, six-pulse, full-wave diode bridge. In a VSI drive, the DC link consists of a capacitor which smoothes out the converter's DC output ripple and provides a stiff input to the inverter. This filtered DC voltage is converted to quasi-sinusoidal AC voltage output using the inverter's active switching elements. VSI drives provide higher power factor and lower harmonic distortion than phase-controlled current-source inverter (CSI) and load-commutated inverter (LCI) drives. VSIs use insulated-gate bipolar transistors (IGBTs) to enable switching required to deliver required voltage/frequency to the AC motor.
[0006] Safety is paramount in all industrial processes. Machineries driven by motors described above need to be handled carefully to avoid injuries and even death. One safety function that is almost universal on all such machines is an emergency stop function which when activated, either manually or through sensors, detects a person’s proximity to the machine or its motor and cuts off torque to the motor by triggering a safety contactor. Of course the contactor- or other contactors- could be triggered to provide a normal stop function as well for different purposes, for example, maintenance.
[0007] However, any contactor itself is a component – and just like any other part to ensure its correct performance it requires proper installation, maintenance and regular testing. If these are carried out incorrectly the contactor can itself fail, meaning that the machine might not stop or torque (machine’s motion) may resume unexpectedly. This is of course highly dangerous, for example, when maintenance of the machine/ associated assemblies is being carried out. When using a Variable Frequency Drive as elaborated above, Safe Torque Off (STO) brings the stopping function of the contactor into the drive itself, so that when a machine is instructed to stop- by triggering proximity sensors, for example- the drive itself shuts down the power to its motor, thus stopping the machine. It cannot then be restarted until the operator instructs it to.
[0008] Hence, once STO has been activated, an operator can be certain that no torque-generating energy can reach the motor, and if the motor cannot turn then the machine(s) coupled to the motor cannot move. This enables safe access to the machine’s moving parts for maintenance, cleaning etc. It should be understood that whilst STO prevents torque in the motor, it does not disconnect the VFD itself from the electrical power supply, and so any access to the electrical parts of the drive or the motor should only be attempted once the drive system has been isolated from the main supply. However this function in itself also means that, once STO is activated, the drive is ready at a moment’s notice to resume normal operations.
[0009] Present devices using means other than STO to stop motors require high capacity electromechanical switches/contactors with consequent high costs. Since they stop the motor abruptly, various components such as control switches of the inverter, motor, insulation etc. are stressed and can suffer damage or have a low operational life. The motor is stopped by storing its rotational energy into energy storing components in the device. Hence zero torque is not truly achieved and failure of the component that stores energy represents another risk.
[00010] While some devices exist for providing STO feature, they rely upon either hardware control or software control, but not both, neither do they provide for an HMI (human machine interface) to enable STO feature easily. Further, they do not provide for redundant STO signal capability and so, if by any chance, a sensor does not trigger signal required by STO, the STO feature itself becomes inoperative.
[00011] Hence there is a need in the art for a system that provides for redundant STO signal capability, can be enabled both via hardware as well as software, and can be controlled via an appropriate HMI.
[00012] All publications herein are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.
[00013] In some embodiments, the numbers expressing quantities or dimensions of items, and so forth, used to describe and claim certain embodiments of the invention are to be understood as being modified in some instances by the term “about.” Accordingly, in some embodiments, the numerical parameters set forth in the written description and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable. The numerical values presented in some embodiments of the invention may contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements.
[00014] As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
[00015] The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.
[00016] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all Markush groups used in the appended claims.

OBJECTS OF THE INVENTION

[00017] Some of the objects of the present disclosure, which at least one embodiment herein satisfies are as listed herein below.
[00018] It is an object of the present disclosure to provide for a safe torque off (STO) system that can be enabled both via hardware as well as software, and can be controlled via an appropriate HMI.
[00019] It is another object of the present disclosure to provide for a system as above that has redundant STO signal capability.
[00020] It is yet another object of the present disclosure to provide for a system as above wherein STO can be implemented with minimum hardware and different safe categories can be implemented using same hardware.
[00021] It is an object of the present disclosure to provide for a system as above wherein a motor using the system is decelerated slowly to stop thereby avoiding damage to various semiconductor switches of voltage source inverter using the system and to the motor itself.

SUMMARY OF THE INVENTION

[00022] The present disclosure relates to systems for controlling alternating current (AC) motors. In particular it pertains to a novel system for providing safe torque off in such motors.
[00023] In an aspect, present disclosure proposes a safe torque off system for an alternating current motor wherein the system can enable safe torque off (STO) using any or a combination of a software control and a hardware control.
[00024] In another aspect, proposed system can provide the software control using a digital logic module and the hardware control using a driver supply regulator.
[00025] In yet another aspect, the digital logic module can further provide for redundancy of signals to trigger the STO.
[00026] In an aspect, various safe categories of the STO can be implemented using same hardware.
[00027] In another aspect, the proposed system can decelerate the alternating current motor slowly to stop upon triggering of the STO.
[00028] In yet another aspect, the proposed system can further provide a Human Machine Interface for implementing the STO.
[00029] In an aspect, the proposed system can provide notification of an STO command to the digital logic module.
[00030] In another aspect, proposed invention elaborates upon a novel method of providing STO (Safe Torque Off) that disables torque generation of AC motor it is implemented upon. The motor stops rotating when the proposed system triggers an STO so that non-electrical maintenance work can be done without switching off the complete drive. The STO system proposed also prevents an unexpected start during such works.
[00031] In yet another aspect, proposed system disables torque generation of the motor through direct removal of power to IGBT (as provided in VSI) through hardware, while at the same time giving intimation to software. Proposed system also provides a provision for disabling of power being provided by IGBT driven VSI entirely through software control.
[00032] In an aspect, proposed system can provide for redundancy of input STO signal in case one signal is faulty. It can stop a motor with controlled deceleration using an appropriately configured HMI (human machine interface) for inverter protection. Further, it can enable direct hardware disabling of inverter power and can implement various safe categories using a single hardware arrangement.
[00033] Various objects, features, aspects and advantages of the present disclosure will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like features.

BRIEF DESCRIPTION OF DRAWINGS

[00034] The accompanying drawings are included to provide a further understanding of the present disclosure, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure. The diagrams are for illustration only, which thus is not a limitation of the present disclosure, and wherein:
[00035] FIG. 1 illustrates control of an AC motor using normal contactors ( Prior Art)
[00036] FIG. 2 illustrates various components of the proposed system to provide STO control in order to elaborate upon its working, in accordance with an exemplary embodiment of the present disclosure.
[00037] FIGs. 3A to 3C provide various safe categories that can be implemented using proposed system by means of flow diagrams, in accordance with an exemplary embodiment of the present disclosure.

DETAILED DESCRIPTION

[00038] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.
[00039] In the following description, numerous specific details are set forth in order to provide a thorough understanding of embodiments of the present invention. It will be apparent to one skilled in the art that embodiments of the present invention may be practiced without some of these specific details.
[00040] Embodiments of the present invention include various steps, which will be described below. The steps may be performed by hardware components or may be embodied in machine-executable instructions, which may be used to cause a general-purpose or special-purpose processor programmed with the instructions to perform the steps. Alternatively, steps may be performed by a combination of hardware, software, and firmware and/or by human operators.
[00041] Embodiments of the present invention may be provided as a computer program product, which may include a machine-readable storage medium tangibly embodying thereon instructions, which may be used to program a computer (or other electronic devices) to perform a process. The machine-readable medium may include, but is not limited to, fixed (hard) drives, magnetic tape, floppy diskettes, optical disks, compact disc read-only memories (CD-ROMs), and magneto-optical disks, semiconductor memories, such as ROMs, PROMs, random access memories (RAMs), programmable read-only memories (PROMs), erasable PROMs (EPROMs), electrically erasable PROMs (EEPROMs), flash memory, magnetic or optical cards, or other type of media/machine-readable medium suitable for storing electronic instructions (e.g., computer programming code, such as software or firmware).
[00042] Various methods described herein may be practiced by combining one or more machine-readable storage media containing the code according to the present invention with appropriate standard computer hardware to execute the code contained therein. An apparatus for practicing various embodiments of the present invention may involve one or more computers (or one or more processors within a single computer) and storage systems containing or having network access to computer program(s) coded in accordance with various methods described herein, and the method steps of the invention could be accomplished by modules, routines, subroutines, or subparts of a computer program product.
[00043] If the specification states a component or feature “may”, “can”, “could”, or “might” be included or have a characteristic, that particular component or feature is not required to be included or have the characteristic.
[00044] As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
[00045] Exemplary embodiments will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments are shown. These exemplary embodiments are provided only for illustrative purposes and so that this disclosure will be thorough and complete and will fully convey the scope of the invention to those of ordinary skill in the art. The invention disclosed may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Various modifications will be readily apparent to persons skilled in the art. The general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the invention. Moreover, all statements herein reciting embodiments of the invention, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Additionally, it is intended that such equivalents include both currently known equivalents as well as equivalents developed in the future (i.e., any elements developed that perform the same function, regardless of structure). Also, the terminology and phraseology used is for the purpose of describing exemplary embodiments and should not be considered limiting. Thus, the present invention is to be accorded the widest scope encompassing numerous alternatives, modifications and equivalents consistent with the principles and features disclosed. For purpose of clarity, details relating to technical material that is known in the technical fields related to the invention have not been described in detail so as not to unnecessarily obscure the present invention.
[00046] Thus, for example, it will be appreciated by those of ordinary skill in the art that the diagrams, schematics, illustrations, and the like represent conceptual views or processes illustrating systems and methods embodying this invention. The functions of the various elements shown in the figures may be provided through the use of dedicated hardware as well as hardware capable of executing associated software. Similarly, any switches shown in the figures are conceptual only. Their function may be carried out through the operation of program logic, through dedicated logic, through the interaction of program control and dedicated logic, or even manually, the particular technique being selectable by the entity implementing this invention. Those of ordinary skill in the art further understand that the exemplary hardware, software, processes, methods, and/or operating systems described herein are for illustrative purposes and, thus, are not intended to be limited to any particular named element.
[00047] Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims. Depending on the context, all references below to the "invention" may in some cases refer to certain specific embodiments only. In other cases it will be recognized that references to the "invention" will refer to subject matter recited in one or more, but not necessarily all, of the claims.
[00048] All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.
[00049] Various terms as used herein are shown below. To the extent a term used in a claim is not defined below, it should be given the broadest definition persons in the pertinent art have given that term as reflected in printed publications and issued patents at the time of filing.
[00050] The present disclosure relates to systems for controlling alternating current (AC) motors. In particular it pertains to a novel system for providing safe torque off in such motors.
[00051] In an aspect, present disclosure proposes a safe torque off system for an alternating current motor wherein the system can enable safe torque off (STO) using any or a combination of a software control and a hardware control.
[00052] In another aspect, proposed system can provide the software control using a digital logic module and the hardware control using a driver supply regulator.
[00053] In yet another aspect, the digital logic module can further provide for redundancy of signals to trigger the STO.
[00054] In an aspect, various safe categories of the STO can be implemented using same hardware.
[00055] In another aspect, the proposed system can decelerate the alternating current motor slowly to stop upon triggering of the STO.
[00056] In yet another aspect, the proposed system can further provide a Human Machine Interface for implementing the STO.
[00057] In an aspect, the proposed system can provide notification of an STO command to the Digital Logic Module.
[00058] In another aspect, proposed invention elaborates upon a novel method of providing STO (Safe Torque Off) that disables torque generation of AC motor it is implemented upon. The motor does not rotate when the safe torque off command is given to the drive so that non-electrical maintenance work can be done without switching off the complete drive. The STO system proposed also prevents an unexpected start during such works.
[00059] In yet another aspect, proposed system disables torque generation of the motor through direct removal of power to IGBT (as provided in VSI) through hardware, while at the same time giving intimation to software. Proposed system also provides a provision for disabling of power being provided by IGBT driven VSI entirely through software control.
[00060] In an aspect, proposed system can provide for redundancy of input STO signal in case one signal is faulty. It can stop a motor with controlled deceleration using an appropriately configured HMI (human machine interface) for inverter protection. Further, it can enable direct hardware disabling of inverter power and can implement various safe categories using a single hardware arrangement.
[00061] Various objects, features, aspects and advantages of the present disclosure will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like features.
[00062] FIG. 1 illustrates control of an AC motor using normal contactors ( Prior Art)
[00063] As illustrated in FIG.1, a power source 102 is connected via contactors 106 of appropriate rating and inverter 108 to an AC motor 104. In the absence of STO feature, these contactors need to be at least of same rating as of the system and hence necessarily incur high cost and maintenance. Besides, electromechanical switches used do not guarantee zero torque as energy may be stored in device even when it is at stop.
[00064] FIG. 2 illustrates various components of the proposed system to provide STO control in order to elaborate upon its working, in accordance with an exemplary embodiment of the present disclosure.
[00065] In an aspect, objective of proposed system is to provide a simpler and more reliable solution for safe torque off in AC motors. The technique must meet the standard of machine drives wherein it is required to remove the torque of the AC motors or any machine wherein emergency stop is required or maintenance of a mechanical part coupled to the motor/machine is required.
[00066] In an aspect, proposed system can comprise an STO control unit, means for disabling the pulses or power supply to the inverter switches, means for initiating shut-down or controlled stop for the motor, and means for detecting the eligibility of the safety signals for applying the safe torque off feature.
[00067] As illustrated in FIG. 2, proposed system can include an STO module 202, a Digital Logic Module 204, a Driver Supply Regulator 206, a controller 208 and a Gate Driver 210. All these components can be operatively connected so that the gate driver 210 can provide appropriate gate drive pulses to a VSI (Voltage Source Inverter) with Rectifier Module 212. Based upon these gate drive pulses, Module 212 can modulate input power it receives from source 102 and accordingly control alternating current motor 104. In an exemplary embodiment, motor 104 can be 3 phase, as illustrated.
[00068] In an aspect, controller 208 can be a 32 bit digital signal processor that can generate gate pulses and gate driver 210 can drive the generated gate pulses to Voltage Source Inverter in module 212. Driver supply regulator 206 can provide logic supply to gate driver 210.
[00069] In another aspect, digital logic module 204 can perform logical functions on received inputs, as required. Module 204 can have an arrangement of digital logic that can provide and detect if a safety command has been received and can also check redundancy of the signals, as elaborated hereunder.
[00070] In yet another aspect, STO module 202 can provide supply disable commands as illustrated at 202A and pulse disable commands as illustrated at 202B.Module 202 can give the two commands based on required safety criteria. These commands can be provided to digital logic module 204 and controller 208 as required.
[00071] In another aspect, digital logic module 204 can include ANDing of two STO signal inputs. Thus failure of only one STO signal would not disable the STO function and both the signals would have to fail for STO function to be disabled. In this fashion, proposed system can provide for redundancy of safety signals. In a similar fashion, by ANDing of multiple signal inputs proposed system can handle multiple safety parameters. Module 204 can implement an OR logic instead, if required, for same purposes, depending upon system design. For example, Module 204 can trigger an STO upon receipt of signal from a proximity sensor or based upon overheating of the motor.
[00072] In an aspect, the driver supply regulator 206 can disable supply to all inverter switches using a hardware implementation to ensure zero torque of motor 104. It can ensure an independent switch on/off of supply to gate driver 210, thus directly disabling gate pulses being provided to the VSI in module 212. Being a hardware implementation, regulator 206 includes no moving part as in case of electromechanical relays/contactors and thus can avoid their disadvantages while simplifying the STO feature implementation.
[00073] In another aspect, proposed system can provide for a controlled stop wherein the motor 104 is decelerated slowly by reducing its input frequency to zero in a gradient. Such controlled stop can avoid damage to various semiconductor switches of the voltage source inverter and to motor 104 itself.
[00074] In yet another aspect, proposed system can provide notification of safe-torque command (STO command) to the digital logic module 204 and accordingly implement fool-proof safe operating logic meeting the standards requirements.
[00075] In an aspect, proposed system can simplify Safe Torque Off implementation, with minimum hardware. Various Safe Categories as elaborated hereunder can be implemented with same hardware.
[00076] In an aspect, proposed system uses less number of sequencing hardware and less circuit components are used to disable power supply to the VSI, that being done through a single power supply enabler IC.
[00077] FIGs. 3A to 3C provide various safe categories that can be implemented using proposed system by means of flow diagrams, in accordance with an exemplary embodiment of the present disclosure.
[00078] As illustrated in FIG. 3A, proposed system can implement Safe Category 0 wherein, upon receiving an STO interrupt command the STO module 202 can supply driver supply off command to digital logic module 204 that can in turn provide a signal to driver supply regulator 206 to switch off supply to gate driver 210.
[00079] Once supply to gate driver 210 is switched off, motor 104 can be brought to an abrupt stop and maintenance work as required can be carried out. Controller 208 can wait for reset command, upon receipt of which it can re-initialize the system.
[00080] As illustrated in FIG. 3B, proposed system can implement Safe Category 1 wherein, upon receiving an STO interrupt command the STO module 202 can supply a pulse off command to digital logic module 204 and also start a timer. Controller 208 can accordingly decelerate the motor. After time as set in the timer has elapsed, STO module 202 can supply driver supply off command to digital logic module 204 that can in turn provide a signal to driver supply regulator 206 to switch off supply to gate driver 210.
[00081] Once supply to gate driver 210 is switched off, motor 104 can be brought to a stop after decelerating as explained above and maintenance work as required can be carried out. Controller 208 can wait for reset command, upon receipt of which it can re-initialize the system.
[00082] As illustrated in FIG. 3C, proposed system can implement Safe Category 2 wherein, upon receiving an STO interrupt command the STO module 202 can supply pulse off command to digital logic module 204 while controller 208 can start decelerating the motor 104. Controller 208 can maintain and ensure zero torque for the motor 104 and maintenance work can be carried out. Controller 208 can wait for reset command, upon receipt of which it can re-initialize the system.
[00083] As elaborated above, proposed system uses a simple hardware implementation for all Safe Categories 0, 1 and 2. The implementation provides for direct hardware disabling of gate pulses to stop the motor and also redundancy of STO input signals. Proposed system enables controlled stop command to the motor providing for controlled torque removal and protection accordingly to the motor, inverter and associated parts.
[00084] Although the proposed system has been elaborated as above to include all the main modules and components, it is completely possible that actual implementations may include only a part, division or combination of these in various combinations across multiple devices that can be operatively coupled with each other, including in the cloud. Further the modules can be configured in any sequence to achieve objectives elaborated.
[00085] As used herein, and unless the context dictates otherwise, the term “coupled to” is intended to include both direct coupling (in which two elements that are coupled to each other or in contact each other) and indirect coupling (in which at least one additional element is located between the two elements). Therefore, the terms “coupled to” and “coupled with” are used synonymously. Within the context of this document terms “coupled to” and “coupled with” are also used euphemistically to mean “communicatively coupled with” over a network, where two or more devices are able to exchange data with each other over the network, possibly via one or more intermediary device.
[00086] Moreover, in interpreting both the specification and the claims, all terms should be interpreted in the broadest possible manner consistent with the context. In particular, the terms “comprises” and “comprising” should be interpreted as referring to elements, components, or steps in a non-exclusive manner, indicating that the referenced elements, components, or steps may be present, or utilized, or combined with other elements, components, or steps that are not expressly referenced. Where the specification claims refers to at least one of something selected from the group consisting of A, B, C ….and N, the text should be interpreted as requiring only one element from the group, not A plus N, or B plus N, etc.
[00087] While some embodiments of the present disclosure have been illustrated and described, those are completely exemplary in nature. The disclosure is not limited to the embodiments as elaborated herein only and it would be apparent to those skilled in the art that numerous modifications besides those already described are possible without departing from the inventive concepts herein. All such modifications, changes, variations, substitutions, and equivalents are completely within the scope of the present disclosure. The inventive subject matter, therefore, is not to be restricted except in the spirit of the appended claims.

ADVANTAGES OF THE INVENTION

[00088] The present disclosure provides for a safe torque off (STO) system that is enabled both via hardware as well as software, and is controlled via an appropriate HMI.
[00089] The present disclosure provides for a system as above that has redundant STO signal capability.
[00090] The present disclosure provides for a system as above wherein STO is implemented with minimum hardware and different safe categories are implemented using same hardware.
[00091] The present disclosure provides for a system as above that a motor using the system is decelerated slowly to stop thereby avoiding damage to various semiconductor switches of voltage source inverter using the system and to the motor itself.