When the induction motor is fed from the PWM VSI inverter, with and without torque enhancing function, the variations of the starting torque and the starting current versus the starting frequency are analyzed, base...When the induction motor is fed from the PWM VSI inverter, with and without torque enhancing function, the variations of the starting torque and the starting current versus the starting frequency are analyzed, based on the steady state equivalent circuit of the induction motor.The corresponding expressions are derived, and the corresponding curves are also drawn, from which the initial starting frequency range can be determined properly and easily. The initial starting frequency range is the common range, in which the starting torque should be high enough and the starting current low enough.Some other useful formulas are also derived.These results are significant for electrical drive designers to make the starting schemes. The effects of the increase of the stator and the rotor resistances on the starting torque and the initial starting frequency range are also discussed, which is caused by the skin effects of the high order harmonics present in the PWM inverter output voltage.展开更多
The effects of parasitic capacitance in induction motor system are unnoticed when it is fed from the AC line, but they are obvious when supplied directly from a PWM inverter. Consequently, many parasitic problems occu...The effects of parasitic capacitance in induction motor system are unnoticed when it is fed from the AC line, but they are obvious when supplied directly from a PWM inverter. Consequently, many parasitic problems occur, such as motor to earth leakage current, bearing current, incoming line current distortion and uneven distribution of electrical stresses along the winding. On the basis of the uniform transmission line principle, a complete equivalent circuit of the PWM inverter fed motor system is presented, based on which all the capacitive parasitic problems mentioned above are analyzed and simulated by means of PSPICE. All the results are consistent with the existing ones.展开更多
The multiplicity of vector combinations for vectors of combined three-level inverters plays an important role, when deciding on the modulation scheme, to obtain minimum switching per inverter vector change, as describ...The multiplicity of vector combinations for vectors of combined three-level inverters plays an important role, when deciding on the modulation scheme, to obtain minimum switching per inverter vector change, as described in the next Section. This is not possible with reduced common-mode three-level inverter structure, obtained with a five-level cascaded H-bridge configuration, as the space vectors locations do not exhibit multiplicity. Moreover, the proposed configuration requires only two power supplies, whereas the scheme with the five-level H-bridge configuration requires six isolated power supplies.展开更多
The multiplicity of vector combinations for vectors of combined three-level inverters plays an important role, when deciding on the modulation scheme, to obtain minimum switching per inverter vector change, as describ...The multiplicity of vector combinations for vectors of combined three-level inverters plays an important role, when deciding on the modulation scheme, to obtain minimum switching per inverter vector change, as described in the next Section. This is not possible with reduced common-mode three-level inverter structure, obtained with a five-level cascaded H-bridge configuration, as the space vectors locations do not exhibit multiplicity. Moreover, the proposed configuration requires only two power supplies, whereas the scheme with the five-level H-bridge configuration requires six isolated power supplies.展开更多
文摘When the induction motor is fed from the PWM VSI inverter, with and without torque enhancing function, the variations of the starting torque and the starting current versus the starting frequency are analyzed, based on the steady state equivalent circuit of the induction motor.The corresponding expressions are derived, and the corresponding curves are also drawn, from which the initial starting frequency range can be determined properly and easily. The initial starting frequency range is the common range, in which the starting torque should be high enough and the starting current low enough.Some other useful formulas are also derived.These results are significant for electrical drive designers to make the starting schemes. The effects of the increase of the stator and the rotor resistances on the starting torque and the initial starting frequency range are also discussed, which is caused by the skin effects of the high order harmonics present in the PWM inverter output voltage.
文摘The effects of parasitic capacitance in induction motor system are unnoticed when it is fed from the AC line, but they are obvious when supplied directly from a PWM inverter. Consequently, many parasitic problems occur, such as motor to earth leakage current, bearing current, incoming line current distortion and uneven distribution of electrical stresses along the winding. On the basis of the uniform transmission line principle, a complete equivalent circuit of the PWM inverter fed motor system is presented, based on which all the capacitive parasitic problems mentioned above are analyzed and simulated by means of PSPICE. All the results are consistent with the existing ones.
文摘The multiplicity of vector combinations for vectors of combined three-level inverters plays an important role, when deciding on the modulation scheme, to obtain minimum switching per inverter vector change, as described in the next Section. This is not possible with reduced common-mode three-level inverter structure, obtained with a five-level cascaded H-bridge configuration, as the space vectors locations do not exhibit multiplicity. Moreover, the proposed configuration requires only two power supplies, whereas the scheme with the five-level H-bridge configuration requires six isolated power supplies.
文摘The multiplicity of vector combinations for vectors of combined three-level inverters plays an important role, when deciding on the modulation scheme, to obtain minimum switching per inverter vector change, as described in the next Section. This is not possible with reduced common-mode three-level inverter structure, obtained with a five-level cascaded H-bridge configuration, as the space vectors locations do not exhibit multiplicity. Moreover, the proposed configuration requires only two power supplies, whereas the scheme with the five-level H-bridge configuration requires six isolated power supplies.
