查询词典 electromotive force

In order to eliminate direct current drift and saturation problems of pure integrator for back electromotive force,an improved programmable low-pass filter rotor flux estimator was proposed to replace the pure integrator.

为了有效抑制反电动势积分环节所存在的直流偏移和积分饱和问题，采用一个截止频率可根据输出频率进行自调整的低通滤波器来代替传统电压模型磁链观测器中的反电动势积分环节。

When a rotating voltage vector is injected to the motor at standstill, there is a microinching when the voltage phase is line to the direct axis of the motor. Then the current will decrease due to the back electromotive force. The initial mover position is identified by this change.

电压相位和电机直轴重合时，产生的电磁推力超过负载阻力，电机有一微动，由于反电势的作用电流就会降低，通过检测电流矢量的变化来估计动子的初始位置。

The simulation results show that the vector control system based on this improved scheme has better dynamic and static performance. It solves a lot of problems such as larger error in the MRAS based on the back electromotive force when the motor runs across the zero speed and the instability based on the instantaneous reactive power in the regenerating mode and has high estimating precision.

仿真表明基于该方法的矢量控制系统动静态性能好，能有效解决反电动势模型参考自适应方法在速度过零点辨识误差大以及瞬时无功功率模型参考自适应方法在转速给定为负阶跃时转速不稳定问题，转速估计精度高。

The results indicate that back electromotive force increases with increasing current density and decreases by 0.5 V after adding 2% Li2CO3, the feeding period is 15 min measured by the method of electric potential control. Finally, the Al-Li alloy with the lithium content of 7.93% can be obtained by electrolyzing for 3 h at the current density of 0.62 A/cm^2 and at 680 ℃, and the current efficiency can reach 74.1%.

结果表明，反电动势随电流密度增加而增大，加入2%的Li2CO3可使反电动势降低0.5V；通过控制电位法测得加料周期为15 min：在680℃、电流密度为0.62A/平方公分的条件下持续电解3h，最终制得了理含量高达7.93%的铝锉合金，电流效率可达74.1%。

The key points of sensorless technology in PMBLDCM are to study a method which can detect rotor position accurately by simply method in whole speed range. After analyzing current sensorless methods of the PMBLDCM, it is found that those methods are successful at middle and high speed, but they often fail to detect rotor position at low speed when the back electromotive force is small or zero.

纵观目前的永磁无刷直流电机的无位置传感器控制方法，比较成熟而可行的方法多集中于电机在中高速区域运行时，能够较准确估计转子位置；电机处于低速、极低速、静止状态时电加热管，因为反电动势幅值较小或者为零，而无法正常工作。

The thesis first probably explains BrushLess Direct Current Motor, and discusses the related control methods, explains the background and Meaning of back electromotive force which is used in the thesis.Then the thesis expounds the basic component parts,the basic running principle,the running characteristic and transfer function of the BLDCM.And then the thesis detailedly dissertates its research pivot: the simulation of BLDCM system in MATLAB based on the method of Back-EMF and the control system of Digital Signal Processor based on the method of Back-EMF.

本文首先对无刷直流电机进行了概述，并对其相关控制方法进行了讨论，说明本文所采用反电动势法的背景和意义；接着论述了无刷直流电机基本组成环节、基本工作原理、运行特性和传递函数，然后是详述本文研究的重点：基于反电动势法的MATLAB调速系统的仿真以及基于反电动势法的DSP控制系统的实现。

By using the stator currents and back electromotive force as state variables,a T-S fuzzy model and a set of fuzzy rules were firstly transformed to represent the PMSM.

选择全局模糊滑模函数，采用自适应技术对不确定性上界进行估计，所设计全局控制器由T-S模糊局部补偿器与滑模监督控制器构成，给出了自适应律及稳定性的证明。

Based on the electromagnetic induction law, Biot-Savart law and the numerical integration arithmetic, the vector potential of the busbar was calculated and the electromotive force of the planar coil for the single phase and three-phase busbar current was deduced.

根据电磁感应定律和毕奥-萨伐尔定律，运用数值积分算法，求解出汇流排导体矢量磁位，并推导了测量单相和三相汇流排导体电流时直线型线圈的输出表达式。

The conclusion is that inductive electromotive force, gotten from sensor with the distribution regularities of weighting function, is proportional to the average flow velocity in pipe and is not relevant to the distribution of flow velocity when flow velocity is non-central symmetry with the central axis.

得出按权重函数分布规律的传感器，在流速非中心轴对称分布时，感应电势仅与平均流速呈正比，而与流速分布无关的结论，从而从原理上解决电磁流量计了高精度测量的问题。

According to the free-election theory in metal and the Dulong-Petit s law, this article proves the formula of the thermo-electromotive force.

根据杜隆－珀替实验定律对传统的金属自由电子气模型予以修正，导出温差不太大条件下的线性电阻温差电动势公式。

Objective To investigate the relationship between ovum fertilization rate and sperm morphology, acrosome reaction in IVF and to explore the influence of parameters of sperm on fertilization rate.

目的 研究体外受精(in vitro fertilization，IVF)中精子形态、顶体反应与卵子受精率之间的关系，分析精子各参数在IVF受精率方面的参考意义。

A: I hear Mr. White wants to run for the Presidency!

我听说怀特先生要参加总统竞选！