Systems catching residual energy from an electric coil

Abstract

Energy saving and sustainability have become hot topics nowadays. Electric transportation applications, such as electric vehicles, always pursue higher energy efficiency other than applications with secured power sources. Therefore, lots of research and development work have been carried out to pursue the energy efficiency, such as redesign the motor itself and/or, use electronic techniques. This invention deploys electronic techniques to pursue higher efficiency. To prove the idea and solutions, 2 prototypes using 2-phase and 3-phase PMBLDC motors have been built for the purpose. They disclose the methods to catch the residual energy from an armature and send it back to the rechargeable power sources without affecting the motor's running driven by switching manner. The implementation is simple and cheap. By recycling the residual energy, it extends the run time of battery systems, achieving higher energy efficiency. The benefit is huge, but not limited to, in economical and environmental fields.

Claims

1. A system for catching residual energy stored in an electric coil, the system comprising: An input circuit configured to allow a BEMF energy from the electric coil to the energy storage circuit when the electric coil is disconnected from a driving power source; An energy storage circuit configured to accumulate energy; A switching circuit configured to selectively output energy stored in the energy storage circuit; and A control unit configured to compare the accumulated voltage level of the energy storage circuit to a threshold voltage, and, when the accumulated voltage level is above the threshold voltage, to control the switching circuit to output portion of energy stored in the energy storage circuit to a rechargeable power source.

2. The system according to claim 1, wherein the input circuit comprises a diode, wherein the diode is forward biased as the electric coil is disconnected from a driving power source, and reverse biased as the electric coil is connected to the driving power source.

3. The system according to claim 2, the diode having an anode electrically connected to the electric coil, and a cathode electrically connected to the energy storage circuit, and wherein a voltage level of the energy storage circuit is higher than a voltage level of the driving power source.

4. The system according to any one of the preceding claims, the system comprising two or more input circuits, each input circuit being configured to allow a flow of current from a corresponding electric coil to the energy storage circuit when the corresponding electric coil is disconnected from the driving power source.

5. The system according to any one of the preceding claims, wherein the energy storage circuit comprises one or more capacitors.

6. The system according to any one of the preceding claims, wherein the switching circuit comprises a switching element that is a MOSFET, a transistor or a switch.

7. The system according to any one of the preceding claims, wherein the comparator is a voltage comparator, can be an operational amplifier.

8. The system according to claim 7, wherein the comparator comprises one or more resistors connected to the operational amplifier to produce a hysteresis effect in the comparator.

11. The system according to any one of the preceding claims, wherein the motor is a two-phase permanent magnet brushless DC motor or a three-phase permanent magnet brushless DC motor.

12. The system according to claim 11 wherein the motor is driven by switching manner.

13. The system according to claim 12, wherein the switching manner is PWM driving signals.

14. The system according to claim 11, wherein the electric motor being used in electric transportations.

15. The system according to claim 14, wherein the electric transportations is an electric scooter, an electric bike, or an electric automotive vehicle.

Description

BRIEFLY DESCRIPTION OF DRAWINGS

[0017] Embodiments of the present invention will be described in further detail with reference to the drawings from which further features, embodiments and advantages may be taken. All waveform diagrams are not scaled, rather, they are for qualitative analysis purposes.

[0018] FIG. 1, Functional diagram in-cooperated with inventive systems consist of Power supply battery (1); Electric motor (2); Residual energy capturer (3), Energy storage (4), Energy passing switch (5), Receiving rechargeable battery (6), and a Controller (7).

[0019] FIG. 2, Schematics of 2-phase PMBLDC motor in-cooperated with inventive circuitry.

[0020] FIG. 3, Voltage waveform on the gate terminals of MOSFETs (M1, M1) and BEMF of 2-phase PMBLDC Motor.

[0021] FIG. 4, Schematic Diagram of 3-phase PMBLDC Motor in “Y” configuration in-cooperated with inventive circuitry.

[0022] FIG. 5, a 6-step Driving sequence of 3-phase PMBLDC motor of “Y” configuration and their BEMF waveform associated.

[0023] FIG. 6, Output stage waveforms showing charging operation.

DETAILS OF DESCRIPTION

[0024] The functional operations of this innovation are shown in FIG. 1. The power supply (1) drives the electric motor (2). It is straightforward up to this point. While the motor (2) is running, the catching component (3) connected to windings of motor (2) catches the residual energy and passes to the storage device (4). The controller (7) monitors the energy level in the storage (4) and commands the switch (5) to conduct, passing portion of the energy to the rechargeable power (6) or power supply (1), according to the hysteresis set. The hysteresis is important and necessary to avoid erratic operation of the switch (5). There are two options for the stored energy passing to, either the power supply (1) or receiving battery (6).

[0025] To implement the idea as above in a practical way, a prototype has been built using a popular low-side-drive of 2-phase of PC PMBLDC motor to prove the idea, shown in FIG. 2, as the first example.

[0026] The PC PMBLDC motor with specifications of 6 W and 12 V is used to simulate the running electric motor. The structure of this PC PMBLDC motor is an out-runner type rotor with permanent magnets and the stator has 4 poles wound with 4 coils, 2 coils connected in series forming windings (L1, L2). One end of windings (L1, L2) connects together to power supply, while the other ends connect to D pins of MOSFETs (M1, M2). Some motors may have reversed biased flywheel diodes connected with windings (L1, L2). In this case, we just need to reconnect the cathodes of the existing diodes to the capacitor (C1) as shown in FIG. 2.

[0027] The FIG. 3 illustrates the output waveform related to MOSFETs (M1, M2), and BEMF appears at drain terminals of the MOSFETs (M1, M2). The upper two traces are the voltage at gates terminals, and the bottom trace is the BEMF produced. It appears in high spike voltage at the moment of MOSFETs (M1, M2) being turned off. If those voltage spikes were not controlled, then damages may occur to the system. With flywheel diodes (D1, D2) connected to the storage capacitor (C1), which absorbs the burst energy and smoothes level to the voltage at the capacitor (C1). This configuration achieves multi-goals in one attempt.

[0028] The normal operation of this PC PMBLDC motor is as: MOSFETs (M1, M2) are driven by series of a pulse generated from existing circuitry with hall sensors built-in, energizing windings (L1, L2) exclusively, so does the current flows in the windings (L1, L2). MOSFETs (M1, M2) are operated in a so-called “break before close” manner to avoid confused status, which has been taken care of by the existing circuitry. So far, there is no difference from ordinal PC PMBLDC motor operation and driving circuits, seen in the PC Fan side in FIG. 3.

[0029] Now, let's look at the inventive circuit side. As seen, the invention acts as a portable device to the motor running system. The flywheel diodes (D1, D2) are connected to a storage capacitor (C1) and Windings (L1, L2), as shown in FIG. 3. A voltage comparator (U1) is monitoring the voltage at the capacitor (C1) and will turn to ‘high’ to drive the transistor (Q1) to conduct once reaching the threshold level in the capacitor (C1). This, in turn, drives the P-channel MOSFET (M3) to pass the electric energy stored in capacitor (C1) to the rechargeable battery (V2). The portion of energy in the storage capacitor (C1) to be passed to the battery (V2) is determined by the hysteresis set with a pair of resistors (R3, R4). When the voltage at capacitor (C1) falls below the threshold level, the comparator (U1) will turn to ‘low’, switching off transistor (Q1), so doing to the P-channel MOSFET (M3) to isolate the rechargeable battery (V2) from the system. The pair of resistors (R1, R2) forms a voltage divider for the reference (Ref) connected to the inverted pin to compare with. Diode (D3) is to prevent current flowing back to the system from the receiving power source (V2).

[0030] At the initial start of running the motor, there will be an extra current drawn to charge up the storage capacitor (C1). However, this extra drawing is neglected compared to the long run of the motor. One of the solutions is intentionally to keep the voltage at the storage capacitor (C1) higher than the supply voltage by other means.

[0031] Further, FIG. 5 shows the operations of three output waveforms of this residual energy recycling system, the top trace being the voltage charged to the rechargeable battery source (V2), the middle trace being the voltage levels of the capacitor (C1), and the lower trace being the output waveform of the comparator (U1). During the charging cycle of this system, it is a pulse charging to the rechargeable battery source (V2), and that the voltage level of the capacitor (C1) varies within the hysteresis gap.

[0032] To extend the coverage for other types of motor, a second prototype has been built using a popular PMBLDC 3-phase motor to prove the suitability as another example, which is shown on FIG. 4. The structure of this PC 3-phase PMBLDC motor is also an out-runner type rotor with permanent magnets and the stator has 6 poles wound with 6 windings paired in 3 forming windings (L1-L3), separated each other by 120°. The wiring connection is “Y” and driven by a 6-step waveform generated from 3 half-bridge circuits. Same as the first example, the systems are divided into two parts, the existing 3-phase motor driving system and portable inventive circuitry. As usual, we don't need to concern the 3-phase motor part, leave the existing electronic control systems as they are.

[0033] Now, let's analyze the operation on this 3-phase motor. Referring to FIG. 5, there are always two windings being energized while one winding in floating status marked with “/”, at which time the BEMF occurs and to be captured with one of 6 diodes (D1-D6). The diodes (D1-D6) are configured as a 3-phase full-bridge rectifier, which is to convert the alternative BEMF waveforms to DC for the capacitors (C1, C2) to store, seen in FIG. 5. Capacitors (C1, C2) are connected in series and their common is connected to the common circuit point (Common) of three windings (L1-L3). The rest are the exact same as the 2-phase PMBLDC motor configuration mentioned in the first example.

[0034] Now, let's turn the inventive process, referring to schematic diagram FIG. 4, at start, the circuit point (U) is high while circuit point (W) is low, and circuit point (V) is floating. The current flows from circuit point (U) to circuit point (W) in step 1, energizing windings (L1, L2). In step 2, circuit point (W) is floating, and V is low, now, current flows from U to V, energizing L1 and L3. At the same time, the current flow in winding (L2) is disrupted and the induced BEMF causes the diode (D3) to conduct, charging capacitor (C1) and returns to the circuit point (Common), forming a close loop for the residual current to continue to follow. The other windings follow the same way to charge capacitor (C1) as winging (L2), when the current flows out of the windings and returns to the circuit point (Common), charging capacitor (C1). The current flowing out of windings (L1-L3) situation occurs when circuit points (U, V, W) transiting from low to floating status. The BEMF induced charges capacitor (C1) via diodes (D1-D3).

[0035] Now, let's look at the situation when current flows into the windings. In step 3, circuit point (U) is floating, current in winding (L1) continues to flow into the circuit point (Common), due to BEMF, charging capacitor (C2) via diode (D4) returning to circuit point (U). The other windings with flowing-in current charge C2 via D5, and D6, return to circuit points (W, V), respectively. The current flowing-in of windings (L1-L3) situation occurs when circuit points (U, V, W) transiting from high to floating status. The BEMF induced charges capacitor (C2) via diodes (D4-D6). We can see capacitors (C1, C2) are charged 3 times each per one revolution. Capacitors (C1, C2) are connected in series, the output of voltage being sum of voltages at capacitors (C1, C2) are connected to a voltage divider formed with resistors (R1, R2). The rest and the operations are exact same as the first example.

[0036] All those configurations have the same feature, simple, low cost and easy to implement, can be designed as portable units or integrated into the existing systems. In addition, they are neither affecting nor drawing extra energy from the power source; because they perform the recycling function at the time when the electrical loop of winding is disconnected from the power supply source. Furthermore, the systems can also catch the electric energy by mutual induction in the armature when the motor systems become electric generator, at which occurs by mechanical movement force, such inertial force, as long as the BEMF voltage is higher than supply voltage. From a charging battery point of view, it is an apparent pulse charging method. As known, the pulse charging method has advantages over the constant charging counterpart.