Method for driving a single-phase motor and single-phase motor
By using stator coils and permanent magnet rotors in single-phase motors, combined with drive and control electronics, and adjusting the duty cycle and electrical polarity of the PWM cycle, the phase current measurement problem during the starting phase of sensorless single-phase motors is solved, achieving reliable starting and driving.
Patent Information
- Application Number
- CN201980102573.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2019-11-29
- Publication Date
- 2025-10-10
- Estimated Expiration
- 2039-11-29
AI Technical Summary
Existing technologies have difficulty in reliably starting and driving sensorless single-phase motors. In particular, phase current measurement is challenging during the starting phase.
The system uses an electric motor stator with stator coils and a rotatable permanent magnet motor rotor, combined with switchable drive electronics and control electronics. By adjusting the effective duty cycle and electrical polarity within the PWM cycle, the phase current is measured using a current sensor to ensure reliable measurement during the starting phase.
The reliable starting and driving of single-phase motors in the starting stage is achieved, especially for sensorless single-phase motors, which can accurately measure phase current under low duty cycle conditions and improve the reliability of the drive.
Smart Images
Figure CN114830521B_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a method for driving a single-phase motor, in particular a method for driving a sensorless single-phase motor, and a single-phase motor, in particular a sensorless single-phase motor. Background Art
[0002] A single-phase electric motor typically has a permanent magnet motor rotor that is driven by energizing stator coils of the motor stator with AC drive energy, wherein the drive energy is commutated, i.e., the polarity of the drive energy varies as a function of the current rotational position of the motor rotor. In particular, in sensorless electric motors, i.e., electric motors that do not include any rotor position sensor, the drive energy can be commutated as a function of the phase currents generated by the drive energy in the stator coils.
[0003] Electric motors are typically driven using a pulse-width modulated (PWM) drive energy signal, meaning the drive energy is periodically switched on and off during a defined PWM cycle. In this case, the effective drive energy level is not defined by varying the drive energy amplitude, but rather by the PWM duty cycle, i.e., the effective on-time within one PWM cycle.
[0004] However, because the phase current in a single-phase motor typically exhibits significant transient effects and has a relatively long settling time in response to the switching of drive energy, reliable phase current measurement is impossible, or at least challenging, for traditional motor drive methods based on PWM drive energy signals. Phase current measurement is particularly challenging during the startup phase, when the stator coils are excited with a drive energy signal with a relatively low duty cycle, meaning that the stator coils are only excited for a relatively short time during each PWM cycle. Summary of the Invention
[0005] The technical problem to be solved by the present invention is to reliably start and drive a single-phase motor, in particular a sensorless single-phase motor, by using a PWM drive energy signal.
[0006] The aforementioned object is achieved by a method for operating a single-phase electric motor having the features of claim 1 or a single-phase electric motor having the features of claim 4 .
[0007] A single-phase electric motor according to the present invention has a stationary motor stator with stator coils. Preferably, the motor stator includes a substantially U-shaped ferromagnetic stator body that defines two opposing magnetic poles. Typically, single-phase electric motors have a single stator coil positioned opposite the open end of the U-shaped stator body. Preferably, the motor stator has a laminated stator body, i.e., a stator body made from a stack of ferromagnetic metal sheets.
[0008] The single-phase motor according to the present invention also has a rotatable motor rotor. Typically, the motor rotor is a permanent magnet motor rotor. The motor rotor can be a permanently magnetized, integral rotor body, or alternatively, a ferromagnetic rotor body with at least one attached permanent magnet. Typically, the motor rotor of a single-phase motor has two diametrically opposed magnetic poles.
[0009] The single-phase electric motor according to the invention also has a switchable drive electronics device, which is electrically connected to the stator coil to excite the stator coil. The drive electronics device is designed to excite the stator coil with a PWM drive energy signal having a defined effective duty cycle. Typically, the drive electronics device includes a plurality of semiconductor switches, preferably four semiconductor switches, for selectively electrically connecting the stator coil to a specified supply energy, or electrically disconnecting the stator coil from the supply energy, to generate the PWM drive energy signal. The PWM duty cycle is usually defined as the total on-time within a PWM period. Therefore, the effective duty cycle in this context defines the effective time share of the drive energy signal PWM period during which the stator coil is excited by the supply energy and thus defines the effective drive energy level.
[0010] The drive electronics are further designed to commutate the effective drive energy provided to the stator coil, i.e., to alternate the effective electrical polarity of the drive energy. In particular, the electrical polarity of the drive energy is alternated by selectively electrically connecting a first end or an opposite second end of the stator coil to a supply voltage terminal, wherein the corresponding other end of the stator coil is simultaneously electrically connected to a ground terminal.
[0011] The single-phase electric motor according to the present invention also has a control electronic device for switching the drive electronic device to generate a pwm drive energy signal. In particular, the control electronic device is electrically connected to the semiconductor switch of the drive electronic device and selectively switches the semiconductor switch to generate a pwm drive energy signal with a defined effective duty cycle and commutates the drive energy as needed. Typically, the drive electronic device is switched based on a periodic (preferably triangular) trigger signal, wherein the typically constant and unchanging period of the trigger signal defines the PWM period. In particular, when the trigger signal reaches a defined on / off threshold, the semiconductor switch is typically switched to on / off each time, wherein the threshold and therefore the switching moment are controlled by the control electronic device to provide a defined effective duty cycle and a defined effective electrical polarity of the pwm drive energy signal. The control electronic device typically includes a microcontroller.
[0012] The single-phase electric motor according to the present invention further includes a current sensor for measuring the phase current flowing through the stator coils when the stator coils are energized by the supply energy. Preferably, the current sensor comprises a simple sensing resistor electrically connected in series with the stator coils and includes means for measuring the voltage drop across the sensing resistor. However, the current sensor may be any device that allows measurement of the current flowing through the stator coils.
[0013] The method for driving a single-phase electric motor according to the present invention comprises switching the drive electronics to a first conductive state during a first on-time interval of a PWM cycle of a drive energy signal. In particular, the semiconductor switches of the drive electronics are switched in such a way that the stator coils are energized by the supply energy during the first on-time interval.
[0014] The method for driving a single-phase electric motor according to the present invention further comprises switching the drive electronics to a second conductive state during a second on-time interval of the same PWM cycle. In particular, the semiconductor switches of the drive electronics are switched in such a way that the stator coil is energized by the supply energy during the second on-time interval.
[0015] The method for driving a single-phase electric motor according to the present invention further comprises switching the drive electronics into an off-state between the two on-time intervals. In particular, the semiconductor switches of the drive electronics are switched in such a way that the stator coils are electrically decoupled from the energy supply during the off-state, so that the stator coils are not energized during the off-state.
[0016] The method for driving a single-phase electric motor according to the present invention further comprises measuring the phase current flowing through the stator coil using a current sensor. The phase current can be measured at one or more defined times within the first or second switch-on time interval, or alternatively, the phase current can be measured substantially quasi-continuously.
[0017] Typically, the two on-time intervals of a PWM cycle always have the same interval length, with the interval length of each on-time interval being half the total on-time specified by the defined effective duty cycle. According to the present invention, if the defined effective duty cycle is below a first duty cycle threshold, the two on-time intervals of a PWM cycle of the drive energy signal have different interval lengths to ensure that at least one of the two on-time intervals has an interval length equal to or greater than a defined minimum on-time interval length. In particular, if the total on-time specified by the defined effective duty cycle is shorter than twice the minimum on-time interval length, the interval length of one on-time interval (either the first on-time interval or the second on-time interval) always has the minimum on-time interval length. In this case, the other on-time interval is provided such that the total effective on-time during each PWM cycle conforms to the on-time specified by the defined effective duty cycle.
[0018] According to the present invention, the phase currents are measured during the on-time interval with a defined minimum on-time interval length. The minimum on-time interval length is defined in such a way that, at least at the end of the on-time interval, the phase currents do not exhibit any transient effects. As a result, the actual phase currents can be reliably measured within the on-time interval.
[0019] The method according to the present invention for driving a single-phase motor provides reliable measurement of the actual phase current, independent of the currently defined effective duty cycle. In particular, the method according to the present invention allows reliable measurement of the phase current during the starting phase, during which the motor is driven by a drive energy signal having a relatively low effective duty cycle value. Thus, the method according to the present invention provides reliable starting and driving of single-phase motors, in particular sensorless single-phase motors, using PWM drive energy signals.
[0020] In a preferred embodiment of the invention, a stabilization time of the phase current is determined, wherein a minimum on-time interval length is defined based on the determined stabilization time. The phase current stabilization time is the time required for the phase current to reach a substantially constant current value, i.e., the time for the phase current to no longer exhibit any transient influences. The stabilization time can be measured once during calibration of the electric motor, wherein the measured stabilization time is stored in a data memory of the electric motor, for example in the control electronics. Alternatively or additionally, the current phase current stabilization time can be (continuously) measured during operation of the electric motor. In any case, the minimum on-time interval length is defined as a value that is greater than or at least equal to the measured phase current stabilization time, so as to allow a reliable measurement of the actual phase current at least at the end of the respective on-time interval.
[0021] The motor stator of a single-phase motor typically exhibits a relatively slow electromagnetic response to a drive energy commutation, i.e. after a drive energy commutation, until a reversal of the polarization of the stator magnetic field generated by the stator coils, a relatively long response time is required. In particular, the electromagnetic response time is typically significantly longer compared to the PWM period of the drive energy signal. Thus, a very short reversal of the electrical polarity of the drive energy during a PWM period does not cause a reversal of the stator field polarization, but a weakening of the effective field strength of the stator magnetic field.
[0022] Thus, in a preferred embodiment of the present application, if the defined effective duty cycle is below a second duty cycle threshold, the stator coil is excited with a first electrical polarity during a first on-time interval and with an opposite second electrical polarity during a second on-time interval. In particular, if the total on-time specified by the defined effective duty cycle is shorter than the minimum on-time interval length, during this on-time interval the stator coil is excited with the requested electrical polarity with the minimum on-time interval length and during the shorter other on-time intervals of the PWM period the stator coil has the opposite electrical polarity. In this case, due to the relatively long electromagnetic response time of the motor stator, the effective on-time is essentially defined by the difference of the interval lengths of the two on-time intervals. Thus, the interval length of the shorter on-time interval is provided such that the difference between the two on-time intervals essentially corresponds to the total on-time specified by the defined effective duty cycle. This enables a reliable phase current measurement even for very low duty cycles and thus provides an efficient and reliable starting of the motor.
[0023] The technical problem addressed by the present application is also solved by a single-phase motor as described above, wherein the motor is configured for performing the method for driving a single-phase motor according to one of the preceding claims. BRIEF DESCRIPTION OF DRAWINGS
[0024] Embodiments of the present application are described with reference to the accompanying drawings, in which
[0025] Figure 1 a schematic diagram of a single-phase motor according to the present application is shown, and
[0026] Figure 2 a schematic circuit diagram of the drive electronics of the motor of Figure 1 comprising a plurality of semiconductor switches, and
[0027] Figures 3a-3c schematic time courses of the trigger signals, Figure 2 the switching states of the semiconductor switches and the resulting single PWM period of the pwm drive energy signal of DETAILED DESCRIPTION
[0028] Figure 1 A sensorless single-phase electric motor 10 is shown, which comprises a stationary electromagnetic electric motor stator 12 and a rotatable permanent-magnetic electric motor rotor 14.
[0029] The electric motor stator comprises a ferromagnetic stator body 16 and a single stator coil 18, which is arranged in satellite-like fashion with respect to the electric motor rotor 14 at a bridge portion 20 of the stator body 16. The stator body 16 is essentially provided in U-shape and is designed as a so-called laminated stator body, i.e. the stator body 16 is made of a stack of ferromagnetic metal sheets.
[0030] The electric motor 10 further comprises switchable drive electronics 22 with four semiconductor switches 24a-24d for exciting the stator coil 18 with a pwm drive energy signal E having a defined pwm period P and a defined active duty cycle D.
[0031] The electric motor 10 further comprises control electronics 26 for switching the drive electronics 22, in particular for controlling the semiconductor switches 24a-24d of the drive electronics 22, in order to generate the pwm drive energy signal E for driving the electric motor rotor 14. In particular, the control electronics 26 control the active duty cycle D and the active polarity of the drive energy signal E, wherein the active drive energy polarity is commutated based on a measured phase current flowing through the stator coil 18 at least during a motor start-up phase when the stator coil 18 is excited by the drive electronics 22.
[0032] The electric motor further comprises a current sensor 28 for measuring the phase current flowing through the stator coil 18. Preferably, the current sensor 28 comprises a simple sense resistor and a means for measuring the voltage drop at the sense resistor.
[0033] Figure 2 A schematic circuit diagram of the drive electronics 22 with the four semiconductor switches 24a-24d is shown. The input of the first semiconductor switch 24a is electrically connected to a supply voltage terminal 30, the output of the first semiconductor switch 24a is electrically connected to a first end of the stator coil 18 and to the input of the third semiconductor switch 24c, and the control of the first semiconductor switch 24a is electrically connected to the control electronics 26.
[0034] The input of the second semiconductor switch 24b is electrically connected to the supply voltage terminal 30, the output of the second semiconductor switch 24b is electrically connected to a second end of the stator coil 18 and to the input of the fourth semiconductor switch 24c, and the control of the second semiconductor switch 24b is electrically connected to the control electronics 26.
[0035] The output terminals of the third semiconductor switch 24c and the fourth semiconductor switch 24d are electrically connected to the input terminals of the current sensor 28, and the control terminals of the third semiconductor switch 24c and the fourth semiconductor switch 24d are electrically connected to the control electronics 26, respectively.
[0036] The output terminal of the current sensor 28 is electrically connected to the ground terminal 32, and the sensing terminal of the current sensor 28 is preferably electrically connected to the control electronics 26 for providing a phase current sensing signal to the control electronics 26.
[0037] Each semiconductor switch 24a-24d can be switched between a conductive, on state (1) and a non-conductive, off state (0). The third semiconductor switch 24c is always essentially switched opposite to the first semiconductor switch 24a, and the fourth semiconductor switch 24d is always essentially switched opposite to the second semiconductor switch 24b. Therefore, only the switching states of the first semiconductor switch 24a and the second semiconductor switch 24b are described subsequently.
[0038] If both the first semiconductor switch 24a and the second semiconductor switch 24b have the same switching state, i.e. are switched to the on state or to the off state, the stator coil 18 is not excited.
[0039] If the first semiconductor switch 24a is switched to the on state and the second semiconductor switch 24b is switched to the off state, the first end of the stator coil 18 is electrically connected to the supply voltage terminal, and the second end of the stator coil 18 is electrically connected to the ground terminal 32 via the current sensor 28. As a result, the stator coil 18 is excited with positive polarity supplied energy Es, i.e. with drive energy having a positive polarity.
[0040] If the first semiconductor switch 24a is switched to the off state and the second semiconductor switch 24b is switched to the on state, the second end of the stator coil 18 is electrically connected to the supply voltage terminal, and the first end of the stator coil 18 is electrically connected to the ground terminal 32 via the current sensor 28. As a result, the stator coil 18 is excited with negative polarity supplied energy -Es, i.e. with drive energy having a negative polarity, which means that the current flow direction in the stator coil 18 is reversed compared to the positive polarity supplied energy Es.
[0041] In order to generate a pwm drive energy signal E with a defined PWM period P and a defined effective duty cycle D, the semiconductor switches 24a-24d are switched on the basis of a substantially triangular trigger signal T, wherein the period of the trigger signal T defines the PWM period P. The semiconductor switches 24a, 24b are each switched into the conducting state or into the non-conducting state when the trigger signal T reaches a respective predefined switching threshold. When the trigger signal T reaches a first switching threshold, the first semiconductor switch 24a is switched into the conducting state at a first switching instant Tl. When the trigger signal T reaches a second switching threshold, the second semiconductor switch 24b is switched into the conducting state at a second switching instant T2. When the trigger signal T reaches a third switching threshold, the first semiconductor switch 24a is switched into the non-conducting state at a third switching instant T3. When the trigger signal T reaches a fourth switching threshold, the second semiconductor switch 24b is switched into the non-conducting state at a fourth switching instant T4. The first and second switching thresholds are typically defined at the rising edge of the trigger signal T, while the third and fourth switching thresholds are defined at the falling edge of the trigger signal T.
[0042] The drive electronics 22 is switched into a first on-state during a first on-time interval II defined by the first switching instant Tl and the second switching instant T2. The drive electronics 22 is switched into a second on-state during a second on-time interval I2 defined by the third switching instant T3 and the fourth switching instant t4. During both on-time intervals II, I2, the first switching state SI of the first semiconductor switch 24a is different compared to the second switching state S2 of the second semiconductor switch 24b, so that the stator coil 18 is excited with a positive supply energy Es or a negative supply energy -Es, respectively, depending on which semiconductor switch 24a, 24b is in the conducting state.
[0043] Between both on-time intervals II, I2, the drive electronics 22 is switched into an off-state by switching the first semiconductor switch 24a and the second semiconductor switch 24b into the same switching state (SI = S2, either both conducting or both non-conducting), so that the stator coil 18 is not excited.
[0044] The switching instants Tl -T4, in particular the respective switching thresholds, are controlled by the control electronics 26 in such a way that the total effective on-time of each PWM period P complies with the specification of the currently defined effective duty cycle D, wherein the total effective on-time is defined by the interval lengths ILl, IL2 of the on-time intervals II, I2 and also by the first drive energy polarity EP1 during the first on-time interval II and the second drive energy polarity EP2 during the second on-time interval I2.
[0045] According to the present invention, the phase current stabilization time Ts is determined by analyzing the transient response effect of the phase current caused by the switching of the drive energy. Preferably, the phase current stabilization time Ts is determined during a one-time motor calibration process. The minimum on-time interval length ILmin is defined as a value greater than or at least equal to the determined phase current stabilization time Ts (ILmin>=Ts). In addition, two duty cycle thresholds D1 and D2 are defined based on the minimum interval length ILmin. The first duty cycle threshold D1 is defined in such a way that the total on-time specified by the first duty cycle threshold D1 is slightly greater than or equal to twice the minimum on-time interval length ILmin. The second duty cycle threshold D2 is defined in such a way that the total on-time specified by the second duty cycle threshold D2 is slightly greater than or equal to the minimum on-time interval length ILmin.
[0046] According to the invention, the control electronics 26 switches the drive electronics 22, in particular the semiconductor switches 24a-24d, based on three different switching patterns, wherein the switching pattern provided depends on the currently defined effective duty cycle D. A first switching pattern is provided for a defined effective duty cycle D that is greater than or equal to a first duty cycle threshold value D1 (D>=D1). A second switching pattern is provided for a defined effective duty cycle D that is lower than the first duty cycle threshold value D1 but greater than or equal to a second duty cycle threshold value D2 (D1>D>=D2). A third switching pattern is provided for a defined effective duty cycle D that is lower than the second duty cycle threshold value D2 (D <D2)。
[0047] Figures 3a-3c An exemplary time course of the trigger signal T, the switching states S1 , S2 and the resulting drive energy signal E for one PWM period P is shown for three different switching modes. In all three examples shown, the drive energy signal E has a positive overall effective electrical polarity.
[0048] Figure 3aA first switching pattern is shown, which is provided for a defined active duty cycle Da greater than or equal to a first duty cycle threshold D1 (D >= D1). In this case, both turn-on time intervals II, I2 have the same interval length, which is equal to half of the total on-time specified by the current active duty cycle D (IL1 = IL2 = 0.5 x D's specified total on-time). Furthermore, both turn-on time intervals II, I2 have the same driving energy polarity (EP1 = EP2, both positive here). Since in this case the total on-time specified by the current active duty cycle D is always greater than or equal to twice the minimum interval length ILmin, the interval lengths IL1, IL2 are always greater than or equal to the minimum turn-on time interval length ILmin (IL1 = IL2 > ILmin). In the present embodiment of the invention, both turn-on time intervals II, I2 are also symmetrically provided with respect to the local extremum Te of the trigger signal T.
[0049] Figure 3b A second switching pattern is shown, which is provided for a defined active duty cycle Db below the first duty cycle threshold D1 but greater than or equal to a second duty cycle threshold D2 (D1 > D >= D2). In this case, both turn-on time intervals II, I2 have the same driving energy polarity (EP1 = EP2, both positive here) as for the first switching pattern. However, since in this case the total on-time specified by the current active duty cycle D is shorter than twice the minimum turn-on time interval length ILmin, both turn-on time intervals II, I2 have different interval lengths (IL1 ≠ IL2). The first turn-on time interval II has a first interval length IL1 equal to the defined minimum turn-on time interval length ILmin (IL1 = ILmin) to allow a reliable phase current measurement during the first turn-on time interval II. The second turn-on time interval I2 has a second interval length IL2 equal to the difference between the total on-time specified by the current active duty cycle D and the first interval length IL1 (IL2 = D's specified total on-time - IL1 = D's specified total on-time - ILmin) to comply with the specification of the currently defined active duty cycle D.
[0050] Figure 3cA third switching mode is shown, which is provided for operation below the second duty cycle threshold D2 (D <D2)的所定义的有效占空比Dc。在这种情况下,对于第二开关模式,第一接通时间间隔I1具有当前请求的驱动能量极性(在此为正)并且具有第一间隔长度IL1,其等于定义的最小接通时间间隔长度ILmin(IL1=ILmin),以允许在第一接通时间间隔I1期间进行可靠的相电流测量。然而,由于在这种情况下由当前的有效占空比D指定的总导通时间短于最小接通时间间隔长度ILmin,所以第二接通时间间隔I2具有相比于第一接通时间间隔I1的逆的驱动能量极性(EP2≠EP1),即,定子线圈18在第一接通时间间隔I1期间以所请求的电极性(在此是正的)被激励,并且在第二接通时间间隔I2期间以逆的电极性(在此是负的)被激励,以提供比最小接通时间间隔长度ILmin短的PWM周期P的有效总导通时间。在这种情况下,PWM周期P的有效总导通时间基本上由第一接通时间间隔I1的第一间隔长度IL1和第二接通时间间隔I2的第二间隔长度IL2之间的差来定义,第一接通时间间隔I1具有当前请求的驱动能量极性(在此EP1=正),第二接通时间间隔I2具有逆的驱动能量极性(在此EP2=负)。因此,第二接通时间间隔I2具有第二间隔长度IL2,该第二间隔长度IL2等于第一间隔长度IL1和由当前的有效占空比D指定的总导通时间之间的差(IL2=D的指定的总导通时间-IL1=D的指定的总导通时间-ILmin),以符合当前定义的有效占空比D的规范。
[0051] Figures 3a-3c The switching operations shown in and described above all refer to generating a drive energy signal with a positive requested drive energy polarity. However, the switching pattern according to the present invention is also applicable to generating a drive energy signal with a negative requested drive energy polarity. In this case, the drive energy polarity must be reversed for each of the above-mentioned on-time intervals. In practice, this is achieved by exchanging the order of the switching instants T1, T2 and the switching instants T3, T4 in the switching operation described.
[0052] Regardless of the switching mode used, the phase current is measured by the current sensor 28 at least during the first on-time interval I1, which always has a first interval length IL1 that is greater than or equal to the minimum on-time interval length ILmin. This provides a reliable phase current measurement for each PWM period P of the drive energy signal E, which is independent of the currently defined effective duty cycle D and, therefore, the current operating conditions of the motor 10. This allows reliable starting and driving of the sensorless single-phase motor 10 using the PWM drive energy signal E.
[0053] Reference Signs List
[0054] 10 Electric Motor
[0055] 12 Motor stator
[0056] 14 Motor rotor
[0057] 16 stator body
[0058] 18 stator coil
[0059] 20 Bridge section
[0060] 22 Drive Electronics
[0061] 24a-24d semiconductor switches
[0062] 26 Control electronics
[0063] 28 Current Sensor
[0064] 30 Power supply voltage terminal
[0065] 32 ground terminal
[0066] D Effective PWM duty cycle
[0067] D1, D2 duty cycle threshold
[0068] E pwm driving energy signal
[0069] EP1, EP2 drive energy polarity
[0070] Es, -Es positive / negative polarity energy supply
[0071] I1, I2 on time interval
[0072] IL1, IL2 on-time interval length
[0073] ILmin Minimum on-time interval length
[0074] P PWM period
[0075] S1, S2 switch status
[0076] T trigger signal
[0077] T1-T4 switching time
[0078] Te triggers the local extreme value of the signal
[0079] Ts phase current stabilization time
Claims
1. A method for driving a single-phase electric motor (10), the electric motor (10) comprising: - a stationary electric motor stator (12) having stator coils (18), - a rotatable motor rotor (14), - switchable drive electronics (22) electrically connected to the stator coils (18) for energizing the stator coils (18) with a pulse-width modulated drive energy signal (E) having a defined effective duty cycle to drive the motor rotor (14), - control electronics (26) for switching the drive electronics (22) to generate a pulse-width modulated drive energy signal (E), and - a current sensor (28) for measuring the phase current flowing through the stator coil (18), and The method comprises: - switching the drive electronics (22) to a first conductive state during a first on-time interval (I1) of a pulse width modulation period (P) of the drive energy signal (E), - switching the drive electronics (22) to a second conductive state during a second on-time interval (I2) of the pulse width modulation period (P), - switching the drive electronics (22) to the off state between two on-time intervals (I1, I2), and - measuring the phase current using a current sensor (28), wherein, if the defined effective duty cycle is greater than or equal to a first duty cycle threshold, the two on-time intervals (I1, I2) of one pulse width modulation period (P) have the same interval length (IL1, IL2), and if the defined effective duty cycle is lower than the first duty cycle threshold, the two on-time intervals (I1, I2) of one pulse width modulation period (P) have different interval lengths (IL1, IL2) to ensure that at least one on-time interval (I1) has an interval length (IL1) equal to or greater than a defined minimum on-time interval length (ILmin), and Therein, the phase currents are measured during the switch-on time interval (I1) with a defined minimum switch-on time interval length (ILmin).
2. The method for driving a single-phase electric motor (10) according to claim 1, wherein a stabilization time of the phase current is determined, and wherein a minimum switch-on time interval length (ILmin) is defined as a function of the determined stabilization time.
3. Method for driving a single-phase electric motor (10) according to any one of the preceding claims, wherein: If the defined effective duty cycle is below a second duty cycle threshold, the stator coil (18) is energized with a first electrical polarity during the first on-time interval (I1) and with an opposite second electrical polarity during the second on-time interval (I2).
4. A single-phase motor (10), comprising - a stationary electric motor stator (12) having stator coils (18), - a rotatable motor rotor (14), - switchable drive electronics (22) electrically connected to the stator coils (18) for energizing the stator coils (18) with a pulse-width modulated drive energy signal (E) having a defined effective duty cycle to drive the motor rotor (14), - control electronics (26) for switching the drive electronics (22) to generate a pulse-width modulated drive energy signal (E), and - a current sensor (28) for measuring the phase current flowing through the stator coil (18), in, The electric motor (10) is configured to carry out the method for driving a single-phase electric motor (10) according to any one of the preceding claims.
Citation Information
Patent Citations
Control method of single-phase motor
JP2005176543A
Motor driving apparatus, vacuum cleaner, and hand dryer
US20180316297A1