Electric powertrain with rim traction torque limit protection

Abstract

An electric powertrain (120) includes a power source (122), an electric motor (124), and a multi-speed transmission (130). The powertrain (120) has an electronic controller (140). The controller (140) determines a respective rim traction torque limit (142, 144, 146) for an operating gear of the multi-speed transmission (130), and determines whether the rim traction torque demand exceeds the rim traction torque limit. Upon determining that the rim traction torque demand exceeds the rim traction torque limit, the controller (140) performs (i) shifting the multi-speed transmission (130) to a gear in which the respective rim traction torque limit is at or above the rim traction torque demand, or (ii) reduce the electric motor torque command to a level at which the rim traction torque is below a corresponding rim traction torque limit for an operating gear of the multi-speed transmission (130).

Description

Technical Field

[0001] The present patent disclosure relates generally to a machine having an electric powertrain and, more particularly, to an electric powertrain having a multi-speed transmission and a rimpull limiter protection system. Background Art

[0002] Many machines used in construction and mining environments include a powertrain for actuating traction devices (e.g., tires). More specifically, these powertrains typically include a power source that provides torque to one or more of the traction devices of the machine through a transmission. An internal combustion engine is a commonly used power source in the powertrain of such machines. The maximum transmission output of the powertrain is typically a function of the maximum engine capacity applied across the various gear ratios in the transmission. The speed and torque range of the internal combustion engine input to the transmission is limited, which is determined by the inability of the internal combustion engine to operate below a low idle speed. Therefore, the inherent minimum operating speed of the internal combustion engine produces a minimum transmission input speed design standard, and the transmission will never operate below this minimum transmission input speed design standard. As a result, there is a natural torque limitation for each gear that is limited by the lowest idle speed of the internal combustion engine.

[0003] Internal combustion engines may emit undesirable exhaust emissions and other pollutants during operation. In addition, improving the fuel efficiency of machinery has become increasingly important, for example due to rising costs associated with fossil fuels. One solution to these problems is to use an electric motor to provide torque to the traction device of the machine. However, the use of electric motors in the power train of a machine may cause other challenges. For example, it may be expensive to provide an electric motor of sufficient size to meet the torque and speed requirements of the machine.

[0004] One way to reduce the required size of an electric motor is by using a multi-speed transmission. However, using a multi-speed transmission to transfer torque from an electric motor causes other problems. For example, compared to an internal combustion engine, an electric motor generally has no lower speed limit and therefore has greater capability over the entire speed range of the motor. The battery used to power the electric motor is not speed-restricted. The battery can output full power at zero speed. Therefore, unlike an internal combustion engine, an electric motor can produce high torque at zero speed. As a result, when a multi-speed transmission is used with an electric motor, each of the gears of the multi-speed transmission may be subjected to relatively high motor torques associated with low motor speeds. However, it is very expensive to construct the gear train of the transmission to be able to withstand such torques.

[0005] U.S. Patent No. 7,766,791 (the "'791 Patent"), assigned to the assignee of the present application, describes a powertrain for a machine having a transmission, a differential coupled to the transmission, and a clutch associated with the differential. The clutch and differential are configured to selectively reduce the total tractive effort available to the machine by releasing the differential in response to torque produced by a power source. More specifically, the powertrain arrangement of the '791 Patent focuses on limiting the torque applied to the powertrain by employing an inter-axle open differential to reduce the tractive effort of the machine in order to prevent the introduction of potentially destructive torque into the powertrain. However, the '791 Patent fails to recognize the problems associated with the potentially destructive torque resulting from the use of a multi-speed transmission with an electric motor in a powertrain of a machine. Summary of the invention

[0006] In one aspect, the present disclosure describes an electric powertrain for driving a traction device of a machine. The electric powertrain includes a power source, an electric motor operably coupled to the power source, and a multi-speed transmission operably coupled to the electric motor. The multi-speed transmission is operable to shift between a plurality of gears, each gear being configured to adjust an electric motor output speed and an electric motor output torque to a corresponding transmission output speed and a transmission output speed range. The electric powertrain also includes an electronic controller. The electronic controller is configured to receive a first signal indicating a rimpull torque demand of the electric powertrain, the rimpull torque demand having an associated electric motor torque command. The electronic controller is further configured to receive a second signal indicating an operating gear in which the multi-speed transmission is operating. The electronic controller determines a corresponding rimpull torque limit for the operating gear of the multi-speed transmission. The electronic controller determines whether the rimpull torque demand exceeds the rimpull torque limit. Upon determining that the rimpull torque demand exceeds the rimpull torque limit, the electronic controller either (i) shifts the multi-speed transmission to a gear having a corresponding rimpull torque limit at or above the rimpull torque demand, or (ii) reduces the electric motor torque command to a level having a rimpull torque below the corresponding rimpull torque limit of the operating gear of the multi-speed transmission.

[0007] In another aspect, the present disclosure describes a machine comprising a machine frame and at least one traction device supported on the machine frame. An electric powertrain is supported on the machine frame for driving the at least one traction device. The electric powertrain comprises a power source, an electric motor operably coupled to the power source, and a multi-speed transmission operably coupled to the electric motor. The multi-speed transmission is operable to shift between a plurality of gears, each gear being configured to adjust an electric motor output speed and an electric motor output torque to a corresponding transmission output speed and a transmission output speed range. The electric powertrain further comprises an electronic controller. The electronic controller is configured to receive a first signal indicating a rimpull torque demand of the electric powertrain, the rimpull torque demand having an associated electric motor torque command. The electronic controller is further configured to receive a second signal indicating an operating gear in which the multi-speed transmission is operating. The electronic controller determines a corresponding rimpull torque limit for the operating gear of the multi-speed transmission. The electronic controller determines whether the rimpull torque demand exceeds the rimpull torque limit. Upon determining that the rimpull torque demand exceeds the rimpull torque limit, the electronic controller either (i) shifts the multi-speed transmission to a gear having a corresponding rimpull torque limit at or above the rimpull torque demand, or (ii) reduces the electric motor torque command to a level having a rimpull torque below the corresponding rimpull torque limit of the operating gear of the multi-speed transmission.

[0008] In another aspect, the present disclosure describes a method for controlling an electric powertrain of a machine. The electric powertrain includes a power source, an electric motor, and a multi-speed transmission operable to shift between a plurality of gears, each gear configured to adjust an electric motor output speed and an electric motor output torque to a corresponding transmission output speed and a transmission output speed range. The method includes receiving a first signal indicating a rimpull torque demand of the electric powertrain, the rimpull torque demand having an associated electric motor torque command; and receiving a second signal indicating an operating gear in which the multi-speed transmission is operating. The method also includes determining a corresponding rimpull torque limit of the operating gear of the multi-speed transmission; and determining whether the rimpull torque demand exceeds the rimpull torque limit. Upon determining that the rimpull torque demand exceeds the rimpull torque limit, the method includes either (i) shifting the multi-speed transmission to a gear having a corresponding rimpull torque limit at or above the rimpull torque demand, or (ii) reducing the electric motor torque command to a level at which the rimpull torque is below the corresponding rimpull torque limit of the operating gear of the multi-speed transmission. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 is a side elevation view of an exemplary machine having an electric powertrain according to the present disclosure.

[0010] Figure 2 yes Figure 1 Schematic diagram of the mechanical electric powertrain.

[0011] Figure 3 yes Figure 2 An exemplary graph of speed versus rimpull torque for an electric powertrain.

[0012] Figure 4 is shown for controlling Figure 2 A flow chart of an exemplary method of an electric powertrain. DETAILED DESCRIPTION

[0013] Referring now to the drawings, wherein like reference numerals will refer to like elements wherever possible, Figure 1 The mobile machine 100 is shown in a specific embodiment of a wheel loader, in which case it is used to load, transport, and deliver materials around a work site. However, although the present disclosure focuses on the mobile machine 100 in the embodiment of a wheel loader, aspects of the present disclosure may be applicable to other types of mobile machines that perform some type of operations associated with industries such as mining, construction, agriculture, transportation, etc. For example, the mobile machine 100 may be an off-highway truck, a motor grader, or other material moving machine configured to move around in a work environment.

[0014] In the illustrated embodiment, the machine 100 includes a machine frame 102. To facilitate maneuverability, such as making sharp turns, the machine frame 102 may be an articulated frame in which the front and rear ends are pivotally connected at an articulated joint 104. To enable the machine 100 to be moved around a work surface in a mobile manner, the machine frame 102 may be supported on a plurality of traction devices 106, such as rotatable wheels that may include rubber tires. The wheels may be designated as powered drive wheels for propelling the machine 100, steerable wheels for adjusting the direction of a wheel loader, or a combination thereof. Other suitable embodiments of the machine may include different traction devices 106, such as continuous tracks, which include a closed belt disposed around rollers and / or sprockets, whereby translation of the belt transports the machine over the work surface.

[0015] To contain material during operation, the machine 100 may include a work tool 108, in the illustrated embodiment a bucket, in which case the work tool is operably associated with a lift mechanism 110 that can vertically raise and lower the work tool 108 relative to a work surface. The lift mechanism 110 can be a mechanical linkage assembled from a plurality of rigid links connected by pivot joints that can articulate and move relative to each other to controllably shift or reposition the work tool 108. In particular, the work tool 108 can be pivotally disposed at a distal end of the lift mechanism 110, which in turn can be pivotally connected (via a pivot joint 116) to a front end of the machine frame 102. A tilt mechanism 112 can also be provided to pivot the work tool 108 relative to the lift mechanism 110. In other embodiments of the mobile machine, it should be appreciated that the work tool 108 can be other than a bucket, such as a fork, a blade, a drilling auger, etc.

[0016] In an embodiment, to accommodate an operator and / or operator input devices or controls for operating the machine, the machine 100 may include an onboard operator compartment 114. For example, input devices in the operator compartment 114 may include travel inputs that control mobile travel of the machine 100 and lift inputs that may manipulate the work tool 108. Examples of travel inputs and lift inputs may include hand wheels, joysticks, pedals, levers, knobs, keyboards, etc. The travel inputs may be configured to increase or decrease the travel speed of the machine 100 relative to the direction of travel to accelerate, slow down, and / or stop the travel of the machine.

[0017] refer to Figure 2 To provide power to one or more of the traction devices 106, the machine 100 includes an electric powertrain 120. The illustrated electric powertrain 120 includes a power source 122, which may include, for example, a battery pack supported on the machine frame 102. The battery pack may include one or more rechargeable batteries that store electrical energy, which may be used to drive the operation of the electric powertrain 120 of the machine 100. In other embodiments, the power source 122 may utilize electrical power supplied from, for example, an internal combustion engine operating in series with an associated generator or fuel cell.

[0018] The electric powertrain 120 also includes an electric motor 124 that is also supported on the machine frame 102. In particular, the electric powertrain 120 can be configured so that the power supply 122 provides electrical energy to power the electric motor 124. Although mentioned in the singular, more than one electric motor 124 can be used, such as two or more electric motors mechanically combined via gears or gear trains. The electric motor 124 can be any known AC or DC motor, such as a permanent magnet motor, an induction motor, a switched reluctance motor, or a hybrid configuration of the above, and can also be sealed, brushless and / or liquid-cooled. In addition, in some embodiments, the electric motor 124 can be configured and controlled so that the machine 100 can be slowed when using the electric motor 124 as a generator, thereby converting kinetic energy associated with the wheel loader into electrical energy that can be stored in the power supply 122 or other power storage device.

[0019] In the illustrated embodiment, the electric motor 124 has an associated inverter 126 that is configured to convert and control the power supplied by the power source 122 to the electric motor 124. For example, the inverter 126 may be configured to control the frequency of the power supplied to the electric motor 124, thereby controlling the speed and output torque of the electric motor.

[0020] To further adjust the speed and or torque generated by the electric motor 124, the electric powertrain 120 may include a multi-speed transmission 130. More specifically, the multi-speed transmission 130 may include a gear train or gearbox supported on the machine frame 102 that facilitates adjusting the power generated by the electric motor 124 and transmitting it to the traction device 106 of the machine 100. The multi-speed transmission 130 may be adapted to be operably coupled to the electric motor 124. Such coupling may be achieved, for example, by selectively using one or more clutches, such as a forward travel clutch and a reverse travel clutch. Similar to the power source 122 and the electric motor 124, the multi-speed transmission 130 may be supported on the machine frame 102.

[0021] The multi-speed transmission 130 may define a plurality of different gear ranges that may enable movement of the machine 100 in both a forward direction and a reverse direction. For example, the multi-speed transmission 130 may be configured to adjust the output speed and torque from the electric motor 124 to a plurality of ranges or settings, such as two, three, four or more forward output speed and torque ranges and one reverse speed and torque range.

[0022] The multi-speed transmission 130 may also include a transmission output shaft 132 through which the power output (e.g., rotational power output) received from the electric motor 124 may be delivered to other components of the electric powertrain 120. The transmission output shaft 132 may, in turn, be operably coupled to a differential 134. The differential 134 may then be configured to further deliver the power output to the traction device 106 to facilitate movement of the machine 100.

[0023] To facilitate controlled operation of the electric powertrain 120, the electric powertrain 120 may be operably associated with a control system embodied as an electronic controller 140, which is sometimes referred to as an electronic control module (ECM) or an electronic control unit (ECU). The electronic controller 140 may be a programmable computing device and may include one or more microprocessors for executing software instructions and processing computer-readable data. Examples of suitable microprocessors include programmable logic devices, such as field programmable gate arrays ("FPGAs"), dedicated or custom logic devices, such as application specific integrated circuits ("ASICs"), gate arrays, complex programmable logic devices, or any other suitable type of circuit or microchip. To store application software and data for controlled operation of the electric powertrain, the electronic controller 140 may include non-transitory computer-readable and / or writable memory, such as read-only memory ("ROM"), random access memory ("RAM"), EPROM memory, flash memory, or another more permanent storage medium, such as a magnetic or optical storage device. To interface and network with other operating systems on the machine 100, the electronic controller 140 may include an input / output interface to electronically send and receive non-transitory data and information. The input / output interface may be physically embodied as a data port, serial port, parallel port, USB port, jack, etc., to communicate via conductive wires, cables, optical fibers, or other communication bus systems via any suitable communication protocol such as CAN bus, WiFi, Bluetooth, or cellular communication standards. The electronic controller 140 may be associated with other software including any suitable instruction set, program, application, routine, library, database, etc. for performing its functions. Although in Figure 2 , electronic controller 140 is shown as a single discrete unit, but in other embodiments, electronic controller 140 and its functionality may be distributed among multiple different and separate components (including various components and functions located on machine 100 and / or at an off-board operator station).

[0024] In this case, the electronic controller 140 communicates with the inverter 126, the electric motor 124, and the multi-speed transmission 130. The data lines of the electronic communication network between the electronic controller 140 and these systems of the electric powertrain 120 are connected at Figure 2It is represented by dotted lines and may embody a CAN bus or similar protocol, and conductive wires or optical fibers may be used as the physical transmission medium.

[0025] In order to protect the electric powertrain 120 from damage or other problems associated with excessive torque, the electronic controller 140 may be configured to limit the rimpull torque generated by the multi-speed transmission 130 under certain circumstances. Specifically, the electronic controller 140 may be configured to impose a predetermined limit on the rimpull torque in one or more of the gears in which the multi-speed transmission 130 is operating. This rimpull torque limit is a function of the gear in which the multi-speed transmission 130 is operating, and represents the maximum rimpull torque that the electronic controller 140 will allow the multi-speed transmission 130 to generate for that particular gear. When a rimpull torque request is received that exceeds the rimpull torque limit, the electronic controller 140 may be configured to instruct the multi-speed transmission 130 to downshift to a gear in which the rimpull torque limit is lower than the rimpull torque request. Alternatively, if a lower gear is not available for some reason (e.g., a failure of one or more of the lower gears, or the multi-speed transmission 130 is already in the lowest gear), the electronic controller 140 may be configured to limit the torque command to the electric motor 124.

[0026] The desired rimpull torque may be considered a machine performance indicator that is a function of the ground speed of the machine 100. When the electric powertrain 120 is configured, each gear of the multi-speed transmission 130 will have a theoretical peak rimpull torque based on the maximum torque (at a given speed) operating envelope multiplied by the gear ratio. In general, this peak rimpull curve may exceed the desired rimpull curve because the available torque / speed envelope of the electric motor 124 is not perfectly matched to the multi-speed transmission 130. As a result, the desired rimpull curve of the machine may be a limitation on the theoretical peak rimpull torque capability of the machine. The rimpull torque limits of the present disclosure do not refer to (or include) such potential differences between the desired rimpull torque and the peak rimpull torque.

[0027] Figure 3 An exemplary graph of transmission output speed and rimpull torque for an electric powertrain 120 having four gears is provided. Figure 3In the example shown, a respective rimpull torque limit is applied to each of the second, third, and fourth gears of the multi-speed transmission 130. The rimpull torque limits are represented by the horizontal lines at the low speed end of the curve for each gear (second gear is shown as 142, third gear is shown as 144, and fourth gear is shown as 146), which illustrate how the rimpull torque stops increasing below a given transmission speed. These transmission speeds may correspond to normal downshift points in each discrete gear. The rimpull torque limits are particularly applicable to speeds below these normal downshift points (at Figure 3 , the downshift point between first and second gear is shown as 160, the downshift point between second and third gear is shown as 162, and the downshift point between third and fourth gear is shown as 164). The rimpull torque limit is generally lower than the maximum rimpull torque capability of the electric motor 124. Figure 3 In the embodiment shown, there is no rimpull torque limiting in first gear, but in some embodiments, first gear may also have rimpull torque limiting.

[0028] For example, in the event that machine 100 is decelerated from its maximum ground speed, multi-speed transmission 130 and electronic controller 140 are designed to shift at appropriate shift points (e.g., Figure 3 160, 162 and 164) to successively lower gears so that the multi-speed transmission 130 produces the desired rimpull curve (minus the horizontal rimpull torque limit lines 142, 144, 146, which can be viewed as Figure 3 170). If the multi-speed transmission 130 is not downshifted for some reason, the desired rimpull torque from a machine perspective will continue to increase as ground speed decreases. In this case, the electronic controller 140 (based on the nominal transmission shift points 160, 162, 164) limits the rimpull torque to the rimpull torque limit 142, 144, 146 of the currently engaged gear and ignores the command to increase rimpull torque associated with slowing the ground speed of the machine.

[0029] Rimpull torque is the force at the connection point between the traction device and the ground. Rimpull torque and transmission output torque are functionally equivalent, where rimpull torque represents the force generated at the traction device for a given transmission output torque. Rimpull torque and transmission output torque are used interchangeably herein.

[0030] Industrial Applicability

[0031] The present disclosure is applicable to any type of electric powertrain. The present disclosure is particularly applicable to electric powertrains having an electric motor and a multi-speed transmission. For example, the rimpull torque limiting of the present disclosure allows one or more gears of the multi-speed transmission to be designed to withstand torques that are less than the full output torque capacity of the electric motor. This rimpull torque limiting system can protect the multi-speed transmission from damage and excessive wear and associated durability issues. This can also significantly reduce the cost of the multi-speed transmission because the rimpull torque limiting system can reduce the need for a hardened design of the multi-speed transmission in which each of the gears and the associated transmission structure can withstand the full torque capacity of the electric motor. The reduced rimpull torque can also signal to the operator of the machine that, for example, there is a fault in the multi-speed transmission that prevents it from properly downshifting.

[0032] refer to Figure 4 And generally in accordance with the previous figures, an exemplary process 150 for applying rimpull torque limiting on the electric powertrain 120 is shown, which exemplary process may be performed by the electronic controller 140. The process 150 depicted in the flowchart for accomplishing these tasks may include a series of steps or instructions that are implemented as non-transitory computer executable software code in the form of an application or program executed by the electronic controller 140. It should be appreciated that the steps of the process 150 do not necessarily have to be performed in accordance with the present invention. Figure 4 Execute in the order shown in .

[0033] In step 152 of process 150, electronic controller 140 receives a signal indicative of a rimpull torque demand of electric powertrain 120. For example, such a rimpull torque demand may be initiated by an operator of machine 100. In step 154, electronic controller 140 receives a signal indicative of the gear currently being operated by multi-speed transmission 130 (e.g., from a multi-speed transmission). Next, in step 156, electronic controller 140 determines a rimpull torque limit applicable to the current gear of multi-speed transmission 130. For example, the rimpull torque limits applicable to each gear of multi-speed transmission 130 may be stored in a lookup table associated with electronic controller 140.

[0034] In step 158, the electronic controller 140 determines whether the rimpull torque demand from step 152 exceeds the rimpull torque limit from step 158. If the desired rimpull torque does not exceed the limit, the process may return to step 152 and the desired rimpull torque may be applied to the multi-speed transmission 130. If the desired rimpull torque does exceed the torque limit, the electronic controller 140 proceeds to reduce the rimpull torque below the rimpull torque limit. One method of accomplishing this is set forth in step 160, where the electronic controller 140 may instruct the multi-speed transmission 130 to shift to a lower gear having a rimpull torque limit that is higher than the current rimpull torque demand. As reflected in step 162, if the multi-speed transmission 130 is able to shift to a lower gear having a rimpull torque limit that is higher than the rimpull torque demand, the process 150 may return to step 152 and the desired rimpull torque may be applied to the multi-speed transmission 130. However, as previously described, there may be situations where the multi-speed transmission 130 is unable or unsuccessful to shift into a lower gear. In such situations, as shown in step 164, the electronic controller 140 may limit the torque command to the electric motor 124 to a level below the rimpull torque limit of the gear in which the multi-speed transmission is operating.

[0035] It should be appreciated that the foregoing description provides examples of the disclosed systems and techniques. However, it is contemplated that other embodiments of the present disclosure may differ in detail from the foregoing examples. All references to the present disclosure or its examples are intended to reference the specific examples discussed at the time, and are not intended to imply any limitation on the scope of the present disclosure more generally. All distinctions and unfavorable remarks about certain features are intended to indicate that these features are not preferred, but unless otherwise indicated, these features are not completely excluded from the scope of the present invention.

[0036] Unless otherwise indicated herein, 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, and each separate 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 clearly contradicted by context.

[0037] The use of the terms "a" and "an" and "the" and "at least one" or the term "one or more" and similar referents in the context of describing the present invention (especially in the context of the following claims) should be interpreted to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by the context. The use of the term "at least one" followed by a list of one or more items (e.g., "at least one of A and B" or "one or more of A and B") should be interpreted to mean one item (A or B) selected from the listed items or any combination of two or more of the listed items (A and B), unless otherwise indicated by the context or clearly contradicted by the context.

[0038] Accordingly, this disclosure includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Additionally, this disclosure encompasses any combination of the above-described elements in all possible variations thereof unless otherwise indicated herein or clearly contradicted by context.

Claims

1. An electric powertrain (120) for driving a traction device (106) of a machine (100), comprising: Power supply (122); an electric motor (124) operably coupled to the power source (122); a multi-speed transmission (130) operably coupled to the electric motor (124), the multi-speed transmission (130) operable to shift between a plurality of gears, each gear being configured to adjust the electric motor output speed and the electric motor output torque to a corresponding transmission output speed and transmission output speed range; as well as An electronic controller (140), the electronic controller being configured to: receiving a first signal indicative of a rimpull torque demand of the electric powertrain (120), the rimpull torque demand having an associated electric motor torque command; receiving a second signal indicating an operating range in which the multi-speed transmission (130) is operating; determining corresponding rimpull torque limits (142, 144, 146) for the operating ranges of the multi-speed transmission (130); determining whether the rimpull torque demand exceeds the rimpull torque limit (142, 144, 146); and Upon determining that the rimpull torque demand exceeds the rimpull torque limit, (i) shifting the multi-speed transmission (130) to a gear having the corresponding rimpull torque limit (142, 144, 146) at or above the rimpull torque demand, or (ii) reducing the electric motor torque command to a level having a rimpull torque below the corresponding rimpull torque limit (142, 144, 146) of the operating gear of the multi-speed transmission (130).

2. The electric powertrain (120) of claim 1, wherein the power source (122) is a battery pack.

3. The electric powertrain (120) of any one of the preceding claims, wherein the rimpull torque limit (142, 144, 146) is lower than the output torque capability of the electric motor (124).

4. The electric powertrain (120) of any preceding claim, further comprising a differential (134) operably coupled to the multi-speed transmission (130) for distributing torque generated by the electric motor (124) to traction devices (106) of the machine (100).

5. The electric powertrain (120) of any one of the preceding claims, further comprising an inverter (126) configured to convert and control the electric power supplied by the power source (122) to the electric motor (124).

6. The electric powertrain (120) of claim 5, wherein the controller (140) is in communication with the electric motor (124), the multi-speed transmission (130), and the inverter (126).

7. The electric powertrain (120) of any preceding claim, wherein the electric motor (124) is also configured to operate as a generator.

8. An electric powertrain (120) as claimed in any preceding claim, wherein a rimpull torque limit (142, 144, 146) for each operating gear is stored in the electronic controller (140).

9. The electric powertrain (120) of any one of the preceding claims, wherein at least the lowest gear of the multi-speed transmission (130) is free of rimpull torque limitation.

10. A machine (100) having an electric powertrain (120) according to claim 1, the machine comprising a machine frame (102), at least one traction device (106) supported on the machine frame (102), and wherein the electric powertrain (120) is supported on the machine frame for driving the at least one traction device.

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