1. A method comprising:
providing a capacitor having a cutout switch to selectively remove the capacitor from electrical connection to a circuitry of a power inverter;
measuring a ripple voltage on the capacitor;
measuring a ripple current through the capacitor;
determining a representative signal from the ripple voltage and current measurements;
determining whether the signal exceeds a predetermined threshold; and
sending an output to a controller if the signal exceeds the predetermined threshold.
2. The method according to claim 1 wherein the ripple current and ripple voltage measurements are provided as inputs to a digital to analog converter and wherein the converter produces and sends the representative signal to a microprocessor to generate the output to the controller.
3. The method according to claim 1 wherein the measuring of ripple current is performed by a rectifier and amplifier module to produce a direct current representative signal.
4. The method according to claim 1 wherein the measuring of ripple voltage is performed by a voltage divider module.
5. The method according to claim 2 further comprising sensing a temperature of the capacitor and sending a temperature signal to the digital to analog converter.
6. The method according to claim 2 further comprising recommending to a master module replacing the capacitor when the controller receives an output from the microprocessor.
7. A power inverter comprising:
a box housing an electrical circuit therein including a dc to ac converter;
at least one electrolytic capacitor mounted to an exterior of the box, the capacitor being connected with the electrical circuit within the box, the capacitor including a cutout switch for selectively removing the capacitor from electrical connection to the circuitry within the box; and
a capacitor health monitoring circuit operably connected to the capacitor to measure a ripple voltage on the capacitor, and
measure a ripple current through the capacitor.
8. The inverter according to claim 7 wherein the monitoring circuit includes a microprocessor programmed to perform operations of:
determining a representative signal from the ripple voltage and current measurements;
determining whether the signal exceeds a predetermined threshold; and
sending an output to a controller if the signal exceeds the predetermined threshold.
9. The inverter according to claim 7 wherein the ripple current and ripple voltage are analyzed in a microprocessor programmed to compare a signal representative of the ripple current and ripple voltage to a predetermined threshold.
10. The inverter according to claim 9 wherein the monitoring circuit issues an output signal when the ripple current and ripple voltage exceed the predetermined threshold.
11. The inverter according to claim 7 wherein the health monitoring circuit has a current sensor in series with the capacitor.
12. The inverter according to claim 7 wherein the health monitoring circuit is connected in parallel with the capacitor.
13. The inverter according to claim 7 wherein the health monitoring circuit includes a temperature sensor operable to sense ambient temperature around the capacitor.
14. A health monitoring system, the system comprising:
a capacitor having a cutout switch to selectively remove the capacitor from electrical connection to a circuitry of a power inverter;
a ripple voltage detector connected across the capacitor;
a ripple current detector connected in series with the capacitor;
a measuring module connected to the voltage and current detectors operable to produce a signal representative of the ripple voltage and current and send an output to a controller if the signal exceeds a predetermined threshold.
15. The system according to claim 14 wherein the measuring module includes an analog-to-digital converter connected to a microprocessor which generates the output to the controller.
16. The system according to claim 14 wherein the ripple voltage detector is a voltage divider module.
17. The system according to claim 16 wherein the ripple current detector is a rectifier and amplifier module.
18. The system according to claim 17 wherein outputs of the voltage divider module and rectifier and amplifier module are fed to an analog-to-digital converter.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. An electric vehicle comprising:
a synchronous electric motor that outputs torque to a first driving wheel;
an induction electric motor that outputs torque to a second driving wheel;
a first inverter that converts first direct current power to alternating current power for driving the synchronous electric motor;
a second inverter that converts second direct current power to alternating current power for driving the induction electric motor;
a vehicle speed sensor that detects a vehicle speed; and
a control portion that controls the torque output from the synchronous electric motor and the torque output from the induction electric motor,
wherein the control portion includes an output torque changing portion that makes the torque output from the synchronous electric motor smaller than the torque output from the induction electric motor when torque is output to the first driving wheel or the second driving wheel and the vehicle speed is close to zero, and that makes the torque output from the synchronous electric motor larger than the torque output from the induction electric motor when torque is output to the first driving wheel or the second driving wheel and the vehicle is moving at or greater than a predetermined speed in a direction opposite a direction in which the vehicle is being operated to move, by the torque output to the first driving wheel and the second driving wheel.
2. The electric vehicle according to claim 1, wherein the predetermined speed is a speed at which a rotation speed of a rotating magnetic field generated in a stator of the induction electric motor is close to zero; and the output torque changing portion of the control portion increases the torque output from the synchronous electric motor and decreases the torque output from the induction electric motor, according to a change in the vehicle speed from close to zero toward the predetermined speed.
3. The electric vehicle according to claim 2, wherein the output torque changing portion of the control portion changes a ratio of the torque output from the synchronous electric motor to the torque output from the induction electric motor according to a ratio of a first voltage of the first direct current power to a second voltage of the second direct current power.
4. The electric vehicle according to claim 3, wherein the first inverter includes a first switching element; the second inverter includes a second switching element; and the output torque changing portion of the control portion changes a ratio of the torque output from the synchronous electric motor to the torque output from the induction electric motor according to a temperature of the first switching element and a temperature of the second switching element.
5. The electric vehicle according to claim 4, wherein the output torque changing portion of the control portion sets a target output torque for the synchronous electric motor and a target output torque for the induction electric motor based on a map in which a ratio of the torque output from the synchronous electric motor to the torque output from the induction electric motor with respect to the vehicle speed has been set beforehand, and then corrects the torque output from the synchronous electric motor and the torque output from the induction electric motor according to i) the ratio of the first voltage of the first direct current power to the second voltage of the second direct current power, or ii) the temperature of the first switching element and the temperature of the second switching element; and the output torque changing portion of the control portion resets the corrected target output torque for the synchronous electric motor and the corrected target output torque for the induction electric motor.
6. The electric vehicle according to claim 1, wherein movement in the direction in which the vehicle is being operated to move is associated with a negative velocity; movement in the direction opposite the direction in which the vehicle is being operated to move is associated with a positive velocity; and the predetermined speed is a positive value.
7. The electric vehicle according to claim 1, wherein the direction in which the vehicle is being operated to move is an uphill.
8. The electric vehicle according to claim 1, wherein the first driving wheel is a front wheel of the vehicle; and the second driving wheel is a rear wheel of the vehicle.