Boost rotor power supply circuit and method for improving pulse motor efficiency

Abstract

A boost circuit and method are described for supplying a boosted voltage to a rotor of an electric machine when the electric machine is pulsed-switched on, the boosted voltage helping the rotor quickly overcome its starting inductance and quickly switch on the rotor. Thus, a much faster transition time is achieved whenever the motor transitions from an off state to an on state at the start of the pulse. By reducing the transition time, the overall efficiency of the motor is significantly improved.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Provisional Application No. 63 / 399,983, filed on August 22, 2022, and is incorporated herein by reference for all purposes. Background Art

[0003] The present application generally relates to pulsed control of a motor, wherein the motor is selectively controlled to operate between an off state and an on state during a pulse, and more specifically, to a boost circuit and method for supplying a boosted voltage to a rotor of the motor when the motor is pulsed on, the boosted voltage helping the rotor to quickly overcome its starting inductance to quickly turn on the rotor, so that the transition time of the motor from the off state to the on state at the beginning of the pulse is much faster.

[0004] Most electric machines typically include a stator with multiple poles and a rotor, and can be operated as either a generator or a motor. When operated as a motor, electrical energy is converted into mechanical energy. When operated as a generator, mechanical energy is converted into electrical energy. Therefore, the terms "electrical machine" or "machine" as used herein are intended to be interpreted broadly to mean both electric motors and generators.

[0005] Electric motors have relatively high energy conversion efficiencies provided they are operated at or near their optimal operating load. However, when operated below their optimal operating load, the energy conversion efficiency can be much lower. Since in many applications electric motors are required to operate below their optimal operating load, the overall efficiency of the machine is reduced, wasting energy required to operate the motor.

[0006] Motor pulse control is a known method of improving motor efficiency. Under selected operating conditions, the motor is intermittently switched from an off state to an on state during pulses. By operating the motor to generate output at a high efficiency level only during the on pulses, the overall efficiency of the machine is improved while generating the required output compared to conventional continuous operation below the optimum operating load of the machine.

[0007] The problem with pulsed control is that a relatively large amount of energy and time is required for each pulse to transition a given motor from the off state to the on state.

[0008] Therefore, there is a need to quickly and efficiently transition motors from an off state to an on state for each pulse, thereby operating such motors at higher efficiency levels. Summary of the invention

[0009] The present application relates to a boost circuit and method for supplying a boost voltage to the rotor of a motor just when the motor is pulsed on, the boost voltage helping the rotor to quickly overcome its starting inductance to quickly turn on the rotor. Therefore, whenever the motor transitions from an off state to an on state at the beginning of a pulse, a much faster transition time is achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The present invention and its advantages may best be understood by referring to the following description in conjunction with the accompanying drawings, in which:

[0011] Figure 1 is a graph illustrating pulsed operation of a motor according to a non-exclusive embodiment of the present invention.

[0012] Figure 2 is a functional block diagram illustrating a motor controller architecture according to a non-exclusive embodiment of the present invention.

[0013] Figure 3 is an operational flow chart illustrating steps implemented by a motor controller according to a non-exclusive embodiment of the present invention.

[0014] Figure 4A is a graph of torque versus efficiency for a motor operating at a fixed speed during the transition from zero to peak efficiency torque.

[0015] Figure 4B is the torque versus work loss relationship for an exemplary motor operating at a fixed speed during the transition from zero to peak efficiency torque.

[0016] Figure 5A is an exemplary boost circuit for boosting a power supply voltage applied to a rotor of a motor according to a non-exclusive embodiment of the present invention.

[0017] Figure 5B is an exemplary voltage rectifier for use by a voltage boost circuit according to a non-exclusive embodiment of the present invention.

[0018] Figure 6 is a flow chart illustrating steps for boosting the supply voltage applied to the rotor of an electric machine during pulsed operation according to a non-exclusive embodiment of the present invention.

[0019] In the drawings, like reference numerals are sometimes used to indicate like structural elements. It should also be understood that the depictions in the drawings are diagrammatic and not drawn to scale. DETAILED DESCRIPTION

[0020] Electric motors and generators are used in a wide variety of applications and under a wide variety of operating conditions. In general, many modern electric motors have relatively high energy conversion efficiencies. However, the energy conversion efficiency of most electric motors can vary greatly based on their operating load. Generally, when operating at or near their peak operating load, the efficiency of the motor is high. However, when operating at lower loads, the efficiency tends to be much lower.

[0021] The present application generally relates to pulsed control of electric machines (e.g., electric motors and generators) to improve their energy conversion efficiency when operating conditions permit. More specifically, under lower load operating conditions, the electric machine is pulsed and intermittently transitions between an off state and an on state during the pulses. By controlling the magnitude, duty cycle, and frequency of the pulses, the electric machine can be controlled to operate only at its higher efficiency level than conventional continuous motor control, thereby delivering a desired average torque output in a more energy efficient manner than before.

[0022] Applicant has filed and received several U.S. patents related to pulsed motor control of electric motors, including U.S. Patent 10,742,155 (TULA P200B), U.S. Patent 11,228,272 (TULA P200C), and U.S. Patent 10,944,352 (TULA P201). Each of the above-listed applications is incorporated herein by reference for all purposes.

[0023] Pulse machine control

[0024] refer to Figure 1 , which shows a graph 10 illustrating the basic operation of a pulsed machine control.

[0025] In this example, several assumptions are made, including:

[0026] The electric machine operates as an electric motor.

[0027] • As plotted along the vertical axis, the maximum torque output of the motor is 50 Nm.

[0028] The motor's peak efficiency range is approximately 95% of its peak output, or approximately 47.5 Nm of torque output.

[0029] In this example, the motor is required to generate an output torque of 10 Nm, which is well below its peak efficiency range.

[0030] Using normal operation, the motor is continuously operated to generate the required torque output of 10 Nm. Figure 1denoted by dashed line 12. A disadvantage of operating continuously at a torque output of 10 is that the motor is operating well below its peak efficiency range (eg, 47.5 Nm or more in this example).

[0031] With pulsed operation, on the other hand, the motor is pulsed on and off. Between the on pulses, the motor is off and generates almost no torque output. During the on pulses, the motor:

[0032] (1) is in the on state and operating at or near its peak efficiency (i.e., 50%); and

[0033] (2) The average torque output of the motor over time (during which the motor is intermittently pulsed between the off state and the on state) is sufficient to meet the determined torque request.

[0034] In this example, the frequency of the on pulses occurs once every five (5) time units (as plotted along the horizontal axis). As a result, the motor is pulsed on twenty percent (20%) of the time, as represented by pulse 14. By operating the motor at its peak output (e.g., 50) every five time units (i.e., twenty percent (20%) of the time), the required 10 Nm of torque is generated over time. However, because the motor is only operated at or near its peak efficiency during the pulses, the overall operating efficiency of the motor is significantly improved over conventional continuous operation.

[0035] Three-phase wound-field synchronous motor

[0036] In a three-phase wound field synchronous motor, the stator may include three coil windings excited by the three-phase AC input and a field winding on the rotor powered by the DC input. When the three-phase AC input passes through the three-phase armature windings, a rotating magnetic field (RMF) is generated. The rate of rotation of the RMF is called the synchronous speed (N) of the motor. s ). The interaction of the field winding field and the armature winding field generates an electromotive force (EMF) that causes the rotor to rotate.

[0037] Power Converters

[0038] refer to Figure 2 , which shows a diagram of a power controller 20 for pulsed operation of an electric machine. The power controller 20 includes a power converter 22, a DC power source 24, and an electric machine 26. In this non-exclusive embodiment, the power converter 22 also includes a pulse controller 28.

[0039] Power converter 22 may operate as a power inverter or a power rectifier depending on the direction of energy flow through the system.

[0040] When the electric machine 26 operates as a motor, the power converter 22 is responsible for generating three-phase AC power from the DC power source 24 to drive the electric machine 26. The three-phase input power, denoted as phase A, phase B and phase C, is applied to the windings of the stator of the electric machine 26 for generating RMF as described above.

[0041] During motor operation, the pulse controller 28 is responsible for selectively pulse-controlling the three-phase input power provided to the motor 26. During normal (i.e., continuous) operation, the three phases A, B, and C of the input power are continuous (i.e., not pulsed). During pulsed operation, the three phases A, B, and C are selectively pulse-controlled.

[0042] When the motor operates as a generator, the power converter 22 operates as a power rectifier, and the AC power from the motor 26 is converted to DC power and stored in the DC power source 24 .

[0043] The line depicting phases A, B, and C is shown with arrows on both ends, indicating that current may flow from power converter 22 to electric machine 26 when the machine is operating as a motor, or in the opposite direction when the machine is acting as a generator.

[0044] Pulse motor control

[0045] refer to Figure 3 , which shows a flow chart 30 showing the steps of the pulse controller 28 in pulse controlling the electric machine 26 when operating as an electric motor.

[0046] In an initial step 32 , the current motor output and the current motor speed are determined.

[0047] In decision step 34, it is determined whether the motor should be operated in continuous mode or pulsed mode based on the current motor output and the current motor speed. In other words, it is determined whether the desired motor torque is above or below the most efficient output torque range for the current motor speed (e.g., Figure 1 47.5Nm in the example).

[0048] In step 36 , if the current motor torque request is above the most efficient output torque for the current motor speed, the motor is operated in the continuous mode.

[0049] In an alternative step 38 , if the current motor torque request is below the most efficient output torque for the current motor speed, the motor is operated in a pulse mode.

[0050] In step 40 , the desired pulse magnitude, duty cycle and frequency for operation in the pulse mode are determined so that the average output power or torque over time matches the desired torque output.

[0051] In step 42 , the motor is operated in a pulse mode using the determined pulse magnitude, duty cycle and frequency of the pulses.

[0052] The above steps 32-42 are performed continuously while the motor is operating. At any given motor speed, there is a corresponding most efficient output torque at which the motor operates at or near its maximum efficiency. As the instantaneous motor output request and / or current motor speed changes, a decision is made to operate the motor in continuous mode or pulsed mode, as appropriate.

[0053] Conceptually, the more often the desired motor torque is lower than the most efficient output torque for the current motor speed, the more significantly the overall efficiency of the motor can be improved by pulsing the motor.

[0054] Pulse rise time

[0055] Current power converters are typically designed for continuous operation, rather than pulsed operation. Such power converters are typically required to transition from an unpowered state to an energized state relatively infrequently. As a result, to date, little design effort has been made to manage the transition time between when the machine is off and when it is pulsed on. Where any such effort has been made, the emphasis has typically been on achieving a smooth transition, rather than a fast transition. As a result, for most motors, the transition from an unpowered (off) state to an energized state (pulsed on) is relatively slow.

[0056] Applicants have discovered that for motor systems that frequently transition from an unpowered state to a peak efficiency state, such as in pulsed operation, further efficiency improvements can be achieved when the transition occurs as quickly as possible. With fast transitions, such as from zero torque to peak efficiency torque, the overall average efficiency is improved because the motor spends less time in the transition where the efficiency is below peak. This relationship is Figure 4A and Figure 4B Depicted in.

[0057] refer to Figure 4A , which shows a torque versus efficiency graph of an exemplary electric machine operating as a motor at a fixed speed (e.g., 6000 rpm). In the exemplary graph, a torque output range from 0.0 Nm to 250 Nm is plotted along the horizontal axis, while the efficiency of the motor from 0.0% to 100% is plotted along the vertical axis. Curve 46 depicts the transition of the motor from zero to peak efficiency torque. During this transition, as depicted by the shaded area 48, the motor operates at a much lower efficiency before reaching or approaching the peak efficiency of the motor as depicted by reference numeral 50.

[0058] refer to Figure 4B, provides a graph showing torque versus work loss for an exemplary motor operating at a fixed speed during a transition from zero to peak efficiency torque. In the graph, work loss (W) is plotted along the vertical axis, while the torque output of the motor is plotted along the horizontal axis. As shown by curve 52, during the transition from zero to peak efficiency torque, the work loss of the motor increases as the torque output increases. Therefore, the faster the transition time from zero to peak efficiency torque, the less work is done, and the less energy is consumed by the electric motor.

[0059] By substituting time for torque along the horizontal axis and then integrating the area under curve 52, the energy consumed by the electric motor for a given transition time can be calculated. For example, for the exemplary motor, 7234.5 joules of energy are used in a transition time of 0.5 seconds, while only 723.4 joules of energy are used in a transition time of 0.05 seconds. This comparison shows that the faster the transition time from zero to peak efficiency torque, the lower the energy consumed in losses. It should be noted that for this example, it is assumed that no acceleration of the load occurs, so no energy is added to the load inertia. Just as efficiency is improved by reducing the rise time, efficiency can also be improved by reducing the pulse fall time.

[0060] The transition from zero to peak efficiency torque, peak efficiency torque, and power loss of the motor will vary from motor to motor. Figure 4A and Figure 4B The relationship diagrams should be regarded as exemplary only, and should not be construed as limiting in any respect.

[0061] Boost rotor supply voltage

[0062] The applicant has found that by applying a boost voltage to the rotor at the beginning of each pulse, the transition time of the motor from the off state to the on state can be significantly reduced. By applying the boost voltage, the inherent on time determined by the inductance and resistance of the rotor is reduced, allowing the windings of the rotor to be quickly energized to the target operating current, thereby generating the desired rotor flux faster than without the boosted rotor voltage. By significantly reducing the transition time from the off state to the on state of each pulse, the overall efficiency of the pulse-controlled motor can be significantly improved.

[0063] As described below, the boost voltage applied to the rotor may be generated or otherwise provided in one of several different ways.

[0064] In one embodiment, an external power source (such as a battery or other power source) can be used to provide the boosted voltage. Alternatively, the boosted voltage can be generated internally in the motor.

[0065] refer to Figure 5A, which shows an exemplary electric machine 80 with a boost circuit 82. In the following explanation, the electric machine 80 is operated as a motor. However, as described above, the electric machine 80 can also be operated as a generator.

[0066] For this embodiment, many existing electrical components of the motor 80, as well as some additional components, are used to generate and store the boost voltage. As described in detail below, a storage device (such as a capacitor) is charged during the off state between pulses. Then, just as the motor begins to transition to the on state through the next on pulse, the charge on the storage device is used to "boost" the supply voltage that would otherwise be applied to the rotor. Therefore, the rotor is turned on faster than if the boost voltage was not used, significantly reducing the transition time of the motor from the off state to the on state. Since most of the existing elements of the motor 80 are used to generate the boost voltage for this embodiment, the benefits of faster transition times are achieved almost "for free", with little overhead in terms of additional circuit systems or components.

[0067] Electric machine 80 includes power converter 22 , pulse controller 28 , a stator 82 having three windings labeled A, B, and C, a rotor 84 , and a DC power source 85 (eg, a battery) coupled to first and second power rails 86 , 88 .

[0068] The power converter 22 includes three sets of transistor-diode pairs, labeled Q1-Q2, Q3-Q4, and Q5-Q6, which generate three-phase AC power from a DC power source 85 to three windings A, B, and C of the stator 82, respectively, as is known in the art.

[0069] As previously described, the pulse controller 28 determines whether the machine 80 should be operated in a continuous mode or a pulse mode. If the latter, the pulse controller 28 determines the magnitude, duty cycle, and frequency of the pulses based on factors such as the current speed of the motor and / or the instantaneous demand on the motor. In response, the pulse controller 28 controls the power converter 22 to selectively energize the windings A, B, and C of the stator 82 as needed to achieve the desired magnitude, duty cycle, and frequency of the pulses. Between pulses, the windings A, B, and C are de-energized and the motor 80 is in the off state. In the continuous mode, the pulse controller 28 directs the power converter 22 to continuously energize the windings A, B, and C of the stator 82.

[0070] Boost circuit 82 includes a rectifier 87, a storage device such as capacitor C1, and a controller 90 coupled between power rail 86 and another power rail 92. In addition, a unidirectional current device such as diode D1 is coupled between rails 86 and 92. For this arrangement, diode D1 allows current to flow from power rail 86 to rail 92, but does not allow current to flow in the reverse direction.

[0071] During pulse mode operation of the motor 80, the pulse controller 28 and the controller 90 cooperate to: (1) recharge the capacitor C1 to the target boost voltage when the motor 80 is in the off state between on pulses, and (2) supply the boost voltage from the capacitor C1 to the rotor 84 at the beginning of the transition of the next on pulse, in addition to the voltage from the DC power supply 85. By using the additional boost voltage at the beginning of the pulse, the rotor 84 is quickly energized and turned on more quickly than when no boost voltage is applied as described above.

[0072] As the rotor is rapidly energized, the charge on capacitor C1 is depleted. Once the rotor 84 has been fully energized, it is powered solely by the DC power supply 85 during the remainder of the on pulse. With this arrangement, the boost voltage is therefore only applied when it is most needed, which means at the start of each pulse when transitioning from the off state to the on state.

[0073] After the motor has transitioned from the on state to the off state at the end of each pulse, the power controller 22 is directed by the pulse controller 28 to energize at least one of the windings A, B, and / or C of the stator 82 for a short period of time, thereby recharging the capacitor C1 in the off state between the on pulses. Normally, during this transition, the winding is simply de-energized. However, by energizing at least one of the windings A, B, and / or C outside of the transition and switching any of the inactive phases to the negative bus voltage on the power rail 88, it induces an AC voltage in the rotor 84 as the rotor moves through the magnetic flux generated by the stator or when the phase is pulsed. In response, the rectifier 87 converts the AC voltage to a DC voltage, which is in turn stored on the storage plates of the capacitor C1. Once the charge on the capacitor C1 reaches the target boost voltage, the controller 90 directs the power converter 22 via the pulse controller 28 to stop energizing one or more windings A, B, and / or C of the stator. Thus, once storage of the target boost voltage is achieved, the controller 90 acts as a voltage clamp for limiting the voltage stored on capacitor C1. As a result, the desired boost voltage is (1) collected and stored on capacitor C1 and (2) available to the rotor 84 at the start of the transition to the on state for the next pulse.

[0074] In various embodiments, after a pulse ends, the excitation of one or more windings A, B, and / or C of the stator 82 may be varied significantly.

[0075] In one non-exclusive embodiment, the excitation is a reverse sinusoidal three-phase voltage waveform that is opposite to the waveform used to drive the motor 80 during a given on-pulse. For example, if the rotor 84 rotates clockwise at 4000 RPM during a given on-pulse, it will continue to rotate at that rate and direction immediately after the given on-pulse ends. If the stator is intentionally excited with a reverse rotating (counterclockwise) 4000 RPM magnetic field after the given on-pulse ends, the net effect is that the rotor 84 effectively rotates at 8000 RPM, which means more pole crossing and higher frequency of the resulting AC voltage induced in the rotor 84. In response, the AC voltage is rectified by the rectifier 87 and the resulting DC voltage is stored on the capacitor C1.

[0076] In yet another embodiment, one (or more) of windings A, B, and C may be statically energized while rotor 84 is rotating. As a result, rotor 84 will generate an AC voltage consistent with each pole crossing.

[0077] In yet another embodiment, windings A, B, and C may be energized using three-phase AC power, but at a lower frequency or speed than the rotation of rotor 84. Thus, the rotor will generate an AC voltage consistent with each pole crossing.

[0078] It should be noted that this document does not exhaustively list all possible embodiments for exciting one or more of the windings A, B, and C. Therefore, those embodiments mentioned herein should not be construed as limiting in any respect. Rather, any embodiment of at least one (or more) of the exciting windings may be used. However, for any such embodiment, at least one (or all) of the non-excited phases are selectively switched to the negative bus voltage on the power rail 88.

[0079] The above process of charging capacitor C1 to the target boost voltage is generally of relatively short duration, typically 2-3 milliseconds, before capacitor C1 is charged to its target boost level. Thereafter, during the remainder of the time that motor 80 is in the off state, one or more windings of the stator are de-energized until the next pulse begins.

[0080] In various embodiments, the magnitude of the boosted voltage collected and stored on capacitor C1 can vary widely. Regardless of the magnitude, the boosted voltage helps reduce the on-time of rotor 84. For example, if DC power source 85 provides 400 volts, and an additional 400 volts are collected and stored on capacitor C1 when motor 80 is in the off state between pulses, a total of 800 volts is available at the beginning of the next on pulse.

[0081] As the next pulse begins, the DC voltage on rail 86 and the boosted voltage on capacitor C1 are combined on rail 92 and provided to rotor 84 via rectifier 87. Using the voltage values ​​provided in the above non-exclusive example, 800 volts are provided to rotor 84 instead of just 400 volts. With the additional 400 volts, the windings of rotor 84 are quickly energized, producing the desired rotor flux much faster than if only 400 volts from power supply 85 were used. Thus, the boosted voltage is available just when more voltage is needed to speed up the turn-on of rotor 84.

[0082] When the windings of the rotor are energized during the starting process, the boost voltage on capacitor C1 is depleted, and thereafter, once the rotor 84 achieves steady-state operation within the remainder of the on pulse, the DC voltage provided by the power supply 85 is used to drive the rotor 84. With this arrangement, the boost voltage is applied to the rotor only when it is most needed, and for a very short period of time. As a result, the start-up time of the rotor is significantly reduced (e.g., typically 2-3 milliseconds) compared to the start-up time of up to 10-100 milliseconds required for a similar but non-boosted motor.

[0083] It should be noted that the on-inductance of the rotor of a given motor is typically much higher than that of its stator, due to the greater number of windings on the rotor relative to the stator. Therefore, the application of the boost voltage is most advantageous when applied to the rotor rather than the stator. However, the boost voltage can also be applied similarly to the stator.

[0084] H-bridge rectifier

[0085] Many electric machines typically rely on a transistor-diode H-bridge to help demagnetize and reduce the generation of back electromotive force (EMF) on the rotor 84. As described below, applicants have discovered that in addition to reducing back EMF, such an H-bridge can also be used (1) as a rectifier to convert the AC voltage generated by the rotor 84 to a DC voltage when charging the storage capacitor C1, and (2) to provide a circuit path for supplying a boost voltage and a supply voltage to the rotor 84 when powered on (e.g., during a conduction pulse or during continuous operation).

[0086] refer to Figure 5B , which shows an H-bridge rectifier 94. The H-bridge rectifier 94 includes a first transistor-diode pair Q7-Q8 and a second transistor-diode pair Q9 and Q10. The remaining components, namely the rotor 84, the DC power supply 85, the first power rail 86 and the second power rail 88, the diode D1, the storage capacitor C1, the controller 90 and the rail 92 operate as described above. In addition, for the sake of clarity, the above-mentioned Figure 5A The remaining components (eg, power converter 22, pulse controller 28, and stator 82) are discussed.

[0087] Immediately following the pulse, the H-bridge rectifier 94 converts the AC voltage generated by the rotor 84 into a DC voltage. When the AC voltage is positive, the diodes associated with transistors Q7 and Q10 are turned on, while the diodes associated with transistors Q8 and Q9 are turned off. When the AC voltage is negative, the diodes associated with transistors Q8 and Q9 are turned on, while the diodes associated with transistors Q7 and Q10 are turned off. The resulting DC voltage is stored on capacitor C1 via power rail 92. When capacitor C1 has reached the target boost voltage, the charging process is stopped as described above, which ideally occurs within 3-5 milliseconds after the end of the on pulse after the rotor drive circuit is disabled.

[0088] Alternatively, the H-bridge rectifier 94 is also used to provide a boost voltage and a supply voltage to the rotor 84 at the beginning of each pulse. This voltage on the supply rail 92 is provided to the rotor 84 by activating the transistor-diode pair Q7 and Q10 or Q9 and Q8. The target boost voltage stored by the capacitor C1 is preferably selected to (1) deliver sufficient current so that the current required by the rotor under nominal operation is achieved in the shortest possible time, and (2) the boost voltage on C1 is fully depleted when the rotor 84 is in nominal steady-state operation, meaning that the rotor 84 is powered only by the supply 84 via the rail 86, the diode D1, the supply rail 92, and the H-bridge rectifier 94. During normal operation (e.g., during continuous operation or once the rotor is fully powered during a pulse), the current in the rotor 84 is controlled by a pulse width modulation (PWM) drive of the H-bridge IGBT Q8 or Q10 as is known in the art.

[0089] It should be noted that when AC to DC rectification occurs, the rotor 84 is effectively demagnetized by the H-bridge rectifier 94, thereby reducing or eliminating back EMF.

[0090] The boost circuit of the present application as described herein can be used in a wide variety of applications, such as, but not limited to, electric vehicles (EVs), variable speed and load industrial motor applications, or any other application where pulse control operation can be used to achieve higher efficiency of the motor. Taking EV as an example, as a general rule, when the electric motor transitions from the off state to the on state at the beginning of each pulse, the faster the transition time, the higher the operating efficiency. With this in mind, components such as capacitor C1 and diode D1 are ideally selected or otherwise defined to achieve a conduction pulse transition time of at least 100 milliseconds, and if possible, a transition time of 10 milliseconds or even less, wherein the body diode or protection diode of the rotor H-bridge acts as a full-wave rectifier, boost voltage monitoring circuit system, and excitation of phases A, B, and / or C of the stator 82 during the off period. To achieve these goals, the size of capacitor C1 can range from 40uF or less to 100uF or more, and the boost voltage stored thereon can range from the bus voltage to any voltage that does not exceed the safe operating voltage of the H-bridge component operating limit with sufficient safety margin. It should be understood that the values ​​described herein are exemplary only and should not be construed as limiting in any respect. Rather, the size of capacitor C1 and the boosted voltage stored thereon may vary widely based on any given application or environmental setting.

[0091] Pulse control operation

[0092] refer to Figure 6 , which shows a flow chart 60 showing steps for boosting the power supply voltage applied to the rotor 84 of the motor 80 .

[0093] In decision step 62, the pulse controller determines whether the current on pulse has ended.

[0094] If the current pulse has ended, then in step 64, the pulse controller 28 transitions the motor 80 to the off state while instructing the power controller 22 to energize one or more windings of the stator 82 using any of the above-described embodiments or any other embodiments not listed herein.

[0095] In step 66 , the rotor 84 generates an AC voltage in response to energizing one or more windings of the stator 82 .

[0096] In step 68 , the rectifier 87 or the H-bridge rectifier 94 rectifies the AC voltage into a DC voltage.

[0097] In step 70 , the storage capacitor C1 is charged with a DC voltage.

[0098] In decision step 72, it is determined whether the capacitor has reached the target boost voltage. If the target has not been reached, charging continues as steps 66 to 70 are repeated. Typically, recharging to the target boost voltage is rapid, taking approximately 2-3 milliseconds.

[0099] In step 74, when the target boost voltage is reached, the stator windings of the stator 82 are de-energized. Thereafter, the stator 82 sleeps in the remainder of the off state until the next on pulse begins.

[0100] In step 76 , the pulse controller 28 determines when the motor is to transition on for the next pulse.

[0101] In step 78, the sum of the boost voltage and the voltage from power supply 85 is provided to the rotor so that it can be turned on quickly. Since the windings of rotor 84 are fully energized when the boost voltage dissipates, only the voltage from power supply 85 is provided to rotor 84 during the remainder of the on pulse.

[0102] Steps 62 to 78 are preferably repeated continuously. In this way, the storage capacitor C1 is continuously recharged to the target boost voltage immediately after the end of each pulse, so that the boost voltage is ready and available to the rotor at the beginning of the next on pulse. Therefore, for each on pulse, the time for transitioning between the off state and the on state is significantly reduced, thereby improving the overall operating efficiency of the motor.

[0103] Applicants have found that using a boosted voltage as described herein has reduced the transition time from the off state to the on state to approximately 2-3 milliseconds, which is a significant improvement over any non-boosted motor equivalent. As a result, the overall efficiency of such motors is significantly improved.

[0104] It should be noted that other longer or shorter transition times may be achieved using the boost described herein.The 2-3 millisecond turn-on times as described herein are illustrative only, and should not be construed in any way as limiting the scope of the present invention in any respect.

[0105] Generator Operation

[0106] Although the above description is primarily directed to the operation of the electric machine as a motor, this should in no way be construed as limiting. Rather, the boosted voltage to the windings of the rotor as described herein may also be used when operating such an electric machine as a generator during pulsed control operation.

[0107] Motor Type

[0108] It should be apparent from the above description that the described boost pulsed machine control can be used in a variety of different applications to improve the energy conversion efficiency of various different types of electric motors and generators. These include both AC and DC motor / generators. Several representative motor types that can benefit from the described boost embodiments of machine pulse control include both asynchronous and synchronous AC motors, including induction motors (IM), switched reluctance motors (SRM), synchronous reluctance motors (SynRM), permanent magnet synchronous reluctance motors (PMaSynRM), hybrid PMaSynRM; externally excited AC synchronous motors (SyncAC), permanent magnet synchronous motors (PMSM), eddy current motors, AC linear motors, AC and DC mechanically commutated motors, axial flux motors, etc. Representative DC motors include brushless DC motors, electrically excited DC motors, permanent magnet DC motors, series-wound DC motors, shunt-excited DC motors, brushed DC motors, compound DC motors, etc.

[0109] Motors and Vehicles

[0110] Electric vehicles are now commonplace and growing in popularity, with some forecasting that they will surpass or completely replace traditional internal combustion engine vehicles within the next decade or two.

[0111] For electric vehicles, one or more on-board motors are provided. When driving the vehicle, the motor acts as a motor to generate torque, which is then used to propel the vehicle. In the case of an electric vehicle, the motor is used exclusively to generate the required torque. The torque can be a positive torque that propels the vehicle, or a negative torque that converts the vehicle's kinetic energy into stored electrical energy. For hybrid vehicles, the on-board motor can be used exclusively, or can be used in conjunction with an internal combustion engine to propel the vehicle. With regenerative braking, the motor is typically used to convert mechanical energy into electrical energy, which is stored in a storage device (such as a battery or capacitor). The stored energy can be used by the motor when the motor is operated as a motor, or alternatively to power other electrical appliances on the vehicle (such as air conditioning, heaters, defrosters, various lighting systems, entertainment systems, etc.).

[0112] Pulsing the onboard motor using the boost voltage described herein is expected to significantly improve efficiency. This increased efficiency can increase the vehicle's range before requiring battery charging and / or refueling, as is the case with hybrid vehicles.

[0113] Additional Embodiments

[0114] Motors used in heating, ventilation, and air conditioning (HVAC) applications are another good example of an application that can benefit from pulsed control. Several factors contribute to pulsed motor control being well suited for HVAC applications. These include the following facts: (a) motors currently used in HVAC applications are primarily induction motors that do not contain permanent magnets; (b) a high percentage of motors used in HVAC applications (particularly including variable speed HVAC condensers and / or air handlers) operate in an operating region below their high efficiency region for a large portion of the time; and (c) the inertia of the fan or pump typically dominates the motor inertia, which tends to further mitigate potential NVH-related effects associated with pulses.

[0115] Although only a few embodiments of the present invention have been described in detail, it should be understood that the present invention may be implemented in many other forms without departing from the spirit or scope of the present invention. In different embodiments, the various pulse controllers and other control elements described may be implemented, grouped, and configured in a variety of different architectures. For example, in some embodiments, the pulse controller may be incorporated into a motor controller or an inverter controller, or it may be provided as a separate component. Similarly, for a generator, the pulse controller may be incorporated into a generator controller or a rectifier controller, and in a combined motor / generator, the pulse controller may be incorporated into a combined motor / generator controller or a combined inverter / rectifier controller. In some embodiments, the control functions described may be implemented in the form of an algorithm in software or firmware executed on a processor, which may take any suitable form, including, for example, a general purpose processor and a microprocessor, a DSP, etc.

[0116] In general, pulsed motor control schemes may be implemented in digital form, in algorithmic form, using analog components, or using a hybrid approach. The pulse generator and / or motor controller may be implemented as code executed on a processor, on programmable logic such as an FPGA (field programmable gate array), in a circuit system such as an ASIC (application specific integrated circuit), on a digital signal processor (DSP), using analog components, or any other suitable hardware. In certain embodiments, the control schemes described may be incorporated into object code for execution on a digital signal processor (DSP) incorporated into an inverter controller (and / or a generator and / or a rectifier controller in the context of a combined inverter / rectifier controller).

[0117] Therefore, the present embodiments are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalents of the appended claims.

Claims

1. A motor, comprising: stator; Rotor; a power converter configured to energize one or more windings of the stator; a pulse controller configured to selectively energize the one or more windings of the stator by controlling the power converter, thereby pulse-controlling the motor between an off state and an on state; as well as a boost circuit configured to store a boost voltage on a storage device when the motor is in the off state between on pulses, and to supply the boost voltage stored on the storage device to the rotor during a transition of the motor from the off state to the on state, The boosted voltage causes the rotor to turn on more quickly relative to a situation where the boosted voltage is not provided to the rotor during the transition, thereby reducing a transition time of the motor during transition from the off state to the on state. 2 . The electric machine of claim 1 , wherein the rotor is further configured to generate an AC voltage after the electric machine transitions from the on-state to the off-state. 3 . The electric machine according to claim 2 , further comprising a rectifier configured to rectify the AC voltage generated by the rotor and store a DC voltage on the storage device of the boost circuit.

4. The electric machine of claim 3, wherein the rectifier is an H-bridge rectifier comprising four transistor-diode pairs arranged in an H-bridge configuration.

5. The electric machine according to any one of claims 1 to 3, wherein the storage device of the boost circuit is a capacitor.

6. The electric machine according to any one of claims 1 to 5, wherein the boost circuit further comprises a controller configured to clamp storage of the boost voltage on the storage device and prevent the boost voltage from exceeding the target boost voltage once the storage device has reached the target boost voltage.

7. An electric machine according to any one of claims 1 to 6, wherein the boost circuit further comprises a controller configured to direct the power converter to energize the one or more windings of the stator within a sufficient period of time after a turn-on pulse to allow the storage device to be charged to the target boost voltage.

8. The electric machine of claim 7, wherein the one or more of the windings of the stator are energized until the storage device is charged to the target boost voltage using one of the following methods: (a) a reverse multi-phase sinusoidal voltage waveform which is opposite to the waveform used to drive the motor during a given on pulse; (b) statically; or (c) energizing using a frequency or speed different from the rotation of the rotor.

9. The electric machine according to any one of claims 1 to 8, wherein the boost circuit further comprises a controller, wherein the controller is configured to: When the electric machine is in the off state, causing the rotor to generate an AC voltage between the conduction pulses by directing the power converter to energize the one or more windings of the stator; and Once the storage device is charged to the target boost voltage, the rotor is stopped from generating the AC voltage by directing the power converter to stop energizing the one or more windings of the stator until the motor begins to transition to the next on pulse.

10. The electric machine according to any one of claims 1 to 9, wherein the stator, the rotor and the power converter are electrically coupled between a first power rail and a second power rail, and a supply voltage is provided on the first power rail by a DC power supply.

11. An electric machine according to any one of claims 1 to 10, wherein the stator has three windings and the power converter provides: When the motor is in the on-state, three-phase power supply to the three windings of the stator during the on-pulse; and Selectively energizing the one or more of the windings of the rotor between the on pulses when the electric machine is in the off state.

12. The electric machine of any one of claims 1 to 11, wherein the boost circuit comprises a rectifier coupled between the rotor and the storage device.

13. An electric motor according to any one of claims 1 to 13, wherein the boost circuit includes a controller configured to control recharging of the storage device in the off state between the conduction pulses of the motor and to stop the recharging of the storage device when the target boost voltage has been reached.

14. The electric machine of any one of claims 1 to 14, wherein the boost circuit maintains the boost voltage stored on the storage device, the storage device being electrically isolated from a power rail providing a supply voltage to the power inverter.

15. An electric machine according to any one of claims 1 to 15, wherein the boost voltage applied to the rotor during the transition of the electric machine from the off state to the on state helps to overcome the turn-on inductance of the rotor, so that the rotor can be turned on faster than when the boost voltage is not applied to the rotor.

16. A method for controlling pulsed operation of a motor, the method comprising: When the motor is pulsed on, a first voltage is applied to the rotor of the motor when the motor changes from an off state to an on state; as well as When the motor is pulsed on, an additional boost voltage is applied to the rotor of the motor when the motor is switched from the off state to the on state, The additional boost voltage helps overcome the turn-on inductance of the rotor, enabling the rotor to turn on faster than if the boost voltage was not applied to the rotor.

17. The method of claim 16, wherein the boost voltage is generated by: When in the off state, inducing the rotor to generate an AC voltage between on pulses of the motor; rectifying the AC voltage into a DC voltage; and When the motor is in the off state, the DC voltage is stored in a storage device between the on pulses, The DC voltage stored in the storage device is used as the boost voltage during the transition of the motor from the off state to the on state.

18. The method of claim 17, further comprising ceasing storage of the DC voltage on the storage device when the storage device has reached a target boost voltage.

19. The method of claim 18, wherein ceasing the storing of the DC voltage on the storage device because the storage device has reached the target boost voltage occurs in three (3) milliseconds or less.

20. The method according to any one of claims 16 to 19, further comprising: (a) energizing at least one winding of a stator when the motor is in the off state between on pulses; (b) generating an AC voltage in the rotor in response to the energization of the at least one winding of the stator when the motor is in the off state between on pulses; (c) rectifying the AC voltage into a DC voltage; as well as (d) The DC voltage is stored in a storage device, and when the motor is pulsed on, the DC voltage on the storage device is used as the boost voltage applied to the rotor when the motor is switched from the off state to the on state.

21. The method of claim 20, further comprising terminating (a) through (d) when the storage device has been charged to a target boost voltage.

22. The method of claim 20, wherein when the motor is in the off state between the on pulses, the energizing of at least one winding of the stator comprises one of the following: (a) a reverse sinusoidal voltage waveform which is opposite to the waveform used to drive the motor during a given on pulse; (b) statically; or (c) energizing using a frequency or speed different from the rotation of the rotor.

23. The method of any one of claims 16 to 22, wherein turning on the rotor with the boosted voltage occurs in three (3) milliseconds or less.

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