Through research on the application of hydroviscous speed-adjusting clutch in belt conveyor, this paper concluded that hydroviscous speed-adjusting clutch has many advantages such as controllable start and stop, overl...Through research on the application of hydroviscous speed-adjusting clutch in belt conveyor, this paper concluded that hydroviscous speed-adjusting clutch has many advantages such as controllable start and stop, overload protection and multi-motor power equilibrium. But its theory when used in large power fan and pump could not meet the needs of belt conveyor soft-start operation. Focusing on the theo- retical analysis of the lubrication oil flow needed by the transmission procedure to form the oil-film. Put forward concrete calculation methods of lubrication flow and how to de- cide number of oil-films used in belt conveyor.展开更多
A fully integrated soft-start circuit for DC-DC buck converters is presented. The proposed high speed soft-start circuit is made of two sections： an overshoot suppression circuit and an inrush current suppression cir...A fully integrated soft-start circuit for DC-DC buck converters is presented. The proposed high speed soft-start circuit is made of two sections： an overshoot suppression circuit and an inrush current suppression circuit. The overshoot suppression circuit is presented to control the input of the error amplifier to make output voltage limit increase in steps without using an external capacitor. A variable clock signal is adopted in the inrush current suppression circuit to increase the duty cycle of the system and suppress the inrush current. The DC-DC converter with the proposed soft-start circuit has been fabricated with a standard 0.13 um CMOS process. Experimental results show that the proposed high speed soft-start circuit has achieved less than 50 us start-up time. The inductor current and the output voltage increase smoothly over the whole load range.展开更多
Induction motors are the most widespread rotating electrical machines in industry.Predictive maintenance of the motors is of crucial importance due to the fact that unexpected faults in those machines can lead to huge...Induction motors are the most widespread rotating electrical machines in industry.Predictive maintenance of the motors is of crucial importance due to the fact that unexpected faults in those machines can lead to huge economic losses for the corresponding companies.Over recent years,there is an increasing use of industrial induction motors operated by different types of drives,which have different functionalities.Among them,the use of soft-starters has proliferated due to the inherent benefits provided by these drives:they damp the high starting currents,enabling the soft startup of the motors and avoiding undesirable commutation transients introduced by other starting modalities.In spite of these advantages,they do not avoid the possible occurrence of rotor damages,one of the most common faults in this type of motors.Few works have proposed predictive maintenance techniques that are aimed to diagnose the rotor condition in soft-started machines and even fewer have demonstrated the validity of their methods in real motors.This work presents,for the first time,the massive validation of a rotor fault diagnosis methodology in soft-started induction motors.Industrial and laboratory and induction motors started under different types of soft-starters and with diverse rotor fault conditions are considered in the work.The results prove the potential of the approach for the reliable assessment of the rotor condition in such machines.展开更多
A fully integrated LED driver based on a current mode PWM boost DC-DC converter with constant output current is proposed. In order to suppress the inrush of current and the overshoot voltage at the start up state, a s...A fully integrated LED driver based on a current mode PWM boost DC-DC converter with constant output current is proposed. In order to suppress the inrush of current and the overshoot voltage at the start up state, a soft-start circuit is adopted. Additionally, to adjust the LED brightness without color variation over the full dimming range and achieve high efficiency, a PWM dimming circuit is presented. Furthermore, to keep the loop stability of the LED driver, an internal slope compensation network is designed to avoid the sub-harmonic oscillation when the duty cycle exceeds 50%. Finally, a UVLO circuit is adopted to improve the reliability of the LED driver against the input voltage changing. The LED driver has been fabricated with a standard 0.5/xm CMOS process, and only occupies 1.21 × 0.76 mm^2. Experimental results show that the brightness of the LED can be adjusted by an off- chip PWM signal with a wide adjusting range. The inductor current and output current increase smoothly over the whole load range. The chip is in the UVLO condition when the input voltage is below 2.18 V and has achieved about 137 μs typical start-up time.展开更多
To improve the power sequencing performance of the system-on-a-chip（SOC）,a novel embedded soft-start circuit is presented.A seamless soft-start reference voltage is obtained with 7 bits DAC,which can not only restra...To improve the power sequencing performance of the system-on-a-chip（SOC）,a novel embedded soft-start circuit is presented.A seamless soft-start reference voltage is obtained with 7 bits DAC,which can not only restrain the turning point overshoot,but also improve the output accuracy and the poor loading capability,reduce the pin number and save PCB area.The whole DC-DC converter has been fabricated in a 0.35μm CMOS process.The measurement results show that the chip starts up successfully with 250μs soft-start time under conditions of 400 kHz switching frequency,2.5 V DC-DC output and 1.8 V LDO output.Stable operation after soft-start is also shown.展开更多
In this paper,a novel method for shock-free soft-start is proposed.The novel method can realize the aim of no-overshoot and inrush of current during the entire soft-start process,thus the start process is safe,stable,...In this paper,a novel method for shock-free soft-start is proposed.The novel method can realize the aim of no-overshoot and inrush of current during the entire soft-start process,thus the start process is safe,stable,and reliable.When the uncontrolled rectification stage ends,a sinusoidal signal synchronized with the grid voltage is generated through dq coordinate transformation and D-axis orientation,then the signal is transmitted to the three-phase inverter bridge.The AC voltage output of the inverter bridge is superimposed on both ends of the soft-start resistor along with the grid.The open-loop control method is adopted to gradually reduce the modulation ratio of the sinusoidal PWM wave until the capacitor voltage on the DC side reaches the rated voltage value,then the soft-start resistor is removed,which means the shock-free soft-start process is completed.Experimental results prove the effectiveness and feasibility of the control strategy proposed in this paper.展开更多
文摘Through research on the application of hydroviscous speed-adjusting clutch in belt conveyor, this paper concluded that hydroviscous speed-adjusting clutch has many advantages such as controllable start and stop, overload protection and multi-motor power equilibrium. But its theory when used in large power fan and pump could not meet the needs of belt conveyor soft-start operation. Focusing on the theo- retical analysis of the lubrication oil flow needed by the transmission procedure to form the oil-film. Put forward concrete calculation methods of lubrication flow and how to de- cide number of oil-films used in belt conveyor.
基金Project supported by the Natural Science Foundation of Jiangsu,China(No.BK2011059)the Program for New Century Excellent Talents in University(NCET- 10-0331)the Qing Lan Project
文摘A fully integrated soft-start circuit for DC-DC buck converters is presented. The proposed high speed soft-start circuit is made of two sections： an overshoot suppression circuit and an inrush current suppression circuit. The overshoot suppression circuit is presented to control the input of the error amplifier to make output voltage limit increase in steps without using an external capacitor. A variable clock signal is adopted in the inrush current suppression circuit to increase the duty cycle of the system and suppress the inrush current. The DC-DC converter with the proposed soft-start circuit has been fabricated with a standard 0.13 um CMOS process. Experimental results show that the proposed high speed soft-start circuit has achieved less than 50 us start-up time. The inductor current and the output voltage increase smoothly over the whole load range.
基金Supported by the Spanish‘Ministerio de Economia y Competitividad’(MINECO)FEDER program in the framework of the‘Proyectos I+D del Subprograma de Generacion de Conocimiento,Programa Estatal de Fomento de la Investigacion Cientifica y Tecnica de Excelencia’(ref:DPI2014-52842-P).”。
文摘Induction motors are the most widespread rotating electrical machines in industry.Predictive maintenance of the motors is of crucial importance due to the fact that unexpected faults in those machines can lead to huge economic losses for the corresponding companies.Over recent years,there is an increasing use of industrial induction motors operated by different types of drives,which have different functionalities.Among them,the use of soft-starters has proliferated due to the inherent benefits provided by these drives:they damp the high starting currents,enabling the soft startup of the motors and avoiding undesirable commutation transients introduced by other starting modalities.In spite of these advantages,they do not avoid the possible occurrence of rotor damages,one of the most common faults in this type of motors.Few works have proposed predictive maintenance techniques that are aimed to diagnose the rotor condition in soft-started machines and even fewer have demonstrated the validity of their methods in real motors.This work presents,for the first time,the massive validation of a rotor fault diagnosis methodology in soft-started induction motors.Industrial and laboratory and induction motors started under different types of soft-starters and with diverse rotor fault conditions are considered in the work.The results prove the potential of the approach for the reliable assessment of the rotor condition in such machines.
基金Project supported by the National Natural Science Foundation of China(No.41274047)the Natural Science Foundation of Jiangsu Province(No.BK2012639)the Changzhou Science and Technology Support(Industrial)Project(No.CE20120074)
文摘A fully integrated LED driver based on a current mode PWM boost DC-DC converter with constant output current is proposed. In order to suppress the inrush of current and the overshoot voltage at the start up state, a soft-start circuit is adopted. Additionally, to adjust the LED brightness without color variation over the full dimming range and achieve high efficiency, a PWM dimming circuit is presented. Furthermore, to keep the loop stability of the LED driver, an internal slope compensation network is designed to avoid the sub-harmonic oscillation when the duty cycle exceeds 50%. Finally, a UVLO circuit is adopted to improve the reliability of the LED driver against the input voltage changing. The LED driver has been fabricated with a standard 0.5/xm CMOS process, and only occupies 1.21 × 0.76 mm^2. Experimental results show that the brightness of the LED can be adjusted by an off- chip PWM signal with a wide adjusting range. The inductor current and output current increase smoothly over the whole load range. The chip is in the UVLO condition when the input voltage is below 2.18 V and has achieved about 137 μs typical start-up time.
文摘To improve the power sequencing performance of the system-on-a-chip（SOC）,a novel embedded soft-start circuit is presented.A seamless soft-start reference voltage is obtained with 7 bits DAC,which can not only restrain the turning point overshoot,but also improve the output accuracy and the poor loading capability,reduce the pin number and save PCB area.The whole DC-DC converter has been fabricated in a 0.35μm CMOS process.The measurement results show that the chip starts up successfully with 250μs soft-start time under conditions of 400 kHz switching frequency,2.5 V DC-DC output and 1.8 V LDO output.Stable operation after soft-start is also shown.
基金Supported by the Natural Science Foundation of Anhui Province(KJ2017A044).
文摘In this paper,a novel method for shock-free soft-start is proposed.The novel method can realize the aim of no-overshoot and inrush of current during the entire soft-start process,thus the start process is safe,stable,and reliable.When the uncontrolled rectification stage ends,a sinusoidal signal synchronized with the grid voltage is generated through dq coordinate transformation and D-axis orientation,then the signal is transmitted to the three-phase inverter bridge.The AC voltage output of the inverter bridge is superimposed on both ends of the soft-start resistor along with the grid.The open-loop control method is adopted to gradually reduce the modulation ratio of the sinusoidal PWM wave until the capacitor voltage on the DC side reaches the rated voltage value,then the soft-start resistor is removed,which means the shock-free soft-start process is completed.Experimental results prove the effectiveness and feasibility of the control strategy proposed in this paper.
