您好,欢迎访问杭州富阳金马电机厂!

新闻资讯  Common problem

联系我们   Content us

联系人:陈铃 女士
联系电话:13073637019
地址:杭州市富阳区 东洲工业园12号路学校沙村363号

新闻资讯
您的位置:首页 >> 新闻资讯 >> 行业资讯 >> 浏览文章
变频器是如何控制电机转速的?
点击:次 上传更新:2017年11月06日

变频器主要由整流(交流变直流)、滤波、再次整流(直流变交流)、制动单元、驱动单元、检测单元微处理单元等组成的。

The frequency converter is mainly composed of rectifier (AC DC converter), filter, re rectification (DC AC converter), brake unit, drive unit, detection unit, micro processing unit and so on.


1. 电机的旋转速度为什么能够自由地改变?

Why is the rotational speed of the 1. motor freely changed?


电机旋转速度单位:r/min 每分钟旋转次数,也可表示为rpm.

Motor rotational speed unit: r/min rotation per minute, also can be expressed as rpm.


例如:2极电机 50Hz 3000 [r/min]

For example: 2 pole motor 50Hz 3000 [r/min]


4极电机 50Hz 1500 [r/min]

4 pole motor 50Hz 1500 [r/min]


结论:电机的旋转速度同频率成比例

Conclusion: the rotation speed of the motor is proportional to the frequency

变频器是如何控制电机转速的?

感应式交流电机(以后简称为电机)的旋转速度近似地确决于电机的极数和频率。由电机的工作原理决定电机的极数是固定不变的。由于该极数值不是一个连续的数值(为2的倍数,例如极数为2,4,6),所以一般不适和通过改变该值来调整电机的速度。

The rotational speed of induction type AC motor (hereafter referred to as motor) approximately determines the pole number and frequency of the motor. The working principle of the motor determines that the number of poles of the motor is fixed. Since the pole value is not a continuous value (multiples of 2, such as the number of poles 2, 4, 6), it is generally uncomfortable and adjusts the speed of the motor by changing the value.


另外,频率能够在电机的外面调节后再供给电机,这样电机的旋转速度就可以被自由的控制。

In addition, the frequency can be adjusted outside the motor and then supplied to the motor, so that the rotation speed of the motor can be controlled freely.


因此,以控制频率为目的的变频器,是做为电机调速设备的优选设备。

Therefore, the frequency converter with the purpose of controlling the frequency is the preferred equipment for the motor speed control equipment.


n = 60f/p

N = 60f/p


n: 同步速度

N: sync speed


f: 电源频率

F: power frequency


p: 电机极对数

Pole count of p: motor


结论:改变频率和电压是最优的电机控制方法

Conclusion: changing frequency and voltage is the best method of motor control


如果仅改变频率而不改变电压,频率降低时会使电机出于过电压(过励磁),导致电机可能被烧坏。因此变频器在改变频率的同时必须要同时改变电压。输出频率在额定频率以上时,电压却不可以继续增加,最高只能是等于电机的额定电压。

If the frequency is changed without changing the voltage, the motor will be burned out due to over voltage (Guo Lici) when the frequency is reduced. Therefore, the converter must change the voltage while changing the frequency. When the output frequency is above the rated frequency, the voltage can not continue to increase, and the maximum is only equal to the rated voltage of the motor.


例如:为了使电机的旋转速度减半,把变频器的输出频率从50Hz改变到25Hz,这时变频器的输出电压就需要从400V改变到约200V

For example: in order to rotate the motor speed by half, the inverter output frequency from 50Hz to 25Hz, then the inverter output voltage needs to change from 400V to about 200V


2. 当电机的旋转速度(频率)改变时,其输出转矩会怎样?

2. what is the output torque when the rotation speed (frequency) of the motor is changed?


变频器驱动时的起动转矩和最大转矩要小于直接用工频电源驱动

The starting torque and the maximum torque of the inverter are less than that of the direct power supply


电机在工频电源供电时起动和加速冲击很大,而当使用变频器供电时,这些冲击就要弱一些。工频直接起动会产生一个大的起动起动电流。而当使用变频器时,变频器的输出电压和频率是逐渐加到电机上的,所以电机起动电流和冲击要小些。

When the motor is powered by the power frequency, the starting and accelerating impact is great, and when the inverter is used, the impact will be weaker. The direct starting of the power frequency will produce a large starting starting current. When the inverter is used, the output voltage and frequency of the inverter are gradually added to the motor, so the starting current and impact of the motor are smaller.


通常,电机产生的转矩要随频率的减小(速度降低)而减小。减小的实际数据在有的变频器手册中会给出说明。

Generally, the torque generated by the motor decreases with the decrease of the frequency (the speed decreases). The reduced actual data will be explained in some frequency converter manuals.


通过使用磁通矢量控制的变频器,将改善电机低速时转矩的不足,甚至在低速区电机也可输出足够的转矩。

By using the flux vector control inverter, the torque of the motor is improved at low speed, and even in the low-speed region, the motor can also output enough torque.


3. 当变频器调速到大于50Hz频率时,电机的输出转矩将降低

3. when the inverter speed is greater than 50Hz frequency, the motor output torque will be reduced


通常的电机是按50Hz电压设计制造的,其额定转矩也是在这个电压范围内给出的。因此在额定频率之下的调速称为恒转矩调速. (T=Te, P<=Pe)

The normal motor is designed and manufactured according to the 50Hz voltage, and its rated torque is also given in this voltage range. Therefore, the speed regulation under rated frequency is called constant torque speed regulation (T=Te, P<=Pe)


变频器输出频率大于50Hz频率时,电机产生的转矩要以和频率成反比的线性关系下降。

When the inverter output frequency is greater than 50Hz frequency, the torque generated by the motor will decline linearly with the frequency.


当电机以大于50Hz频率速度运行时,电机负载的大小必须要给予考虑,以防止电机输出转矩的不足。

When the motor is running at a frequency greater than 50Hz, the magnitude of the motor load must be taken into account to prevent the motor output torque from being insufficient.


举例,电机在100Hz时产生的转矩大约要降低到50Hz时产生转矩的1/2。

For example, the torque generated by the motor at 100Hz will be reduced to about 1/2 when the torque is 50Hz.


因此在额定频率之上的调速称为恒功率调速. (P=Ue*Ie)

Therefore, the speed regulation above the rated frequency is called constant power speed regulation (P=Ue*Ie)


4. 变频器50Hz以上的应用情况

Application of 4. inverter over 50Hz


大家知道, 对一个特定的电机来说, 其额定电压和额定电流是不变的。

As you know, for a specific motor, its rated voltage and rated current are constant.


如变频器和电机额定值都是: 15kW/380V/30A, 电机可以工作在50Hz以上。

Such as inverter and motor ratings are: 15kW/380V/30A, the motor can work more than 50Hz.


当转速为50Hz时, 变频器的输出电压为380V, 电流为30A. 这时如果增大输出频率到60Hz, 变频器的最大输出电压电流还只能为380V/30A. 很显然输出功率不变. 所以我们称之为恒功率调速。

When the speed is 50Hz, the output voltage of the inverter is 380V, the current is 30A. when the output frequency increased to 60Hz, the maximum output voltage and current of inverter is only for 380V/30A. obviously the same output power. So we called the constant power speed.


这时的转矩情况怎样呢?

How about the torque at this moment?


因为P=wT (w:角速度, T:转矩). 因为P不变, w增加了, 所以转矩会相应减小。

Because the P=wT (w: angular speed, T: torque). Because the P does not change, w increases, so the torque will be reduced accordingly.


我们还可以再换一个角度来看:

We can look at it another way:


电机的定子电压 U = E + I*R (I为电流, R为电子电阻, E为感应电势)

The stator voltage of the motor is U = E + I*R (I is current, R is electronic resistance, and E is inductive potential)


可以看出, U,I不变时, E也不变.

It can be seen that E is invariant when U and I are invariant


而E = k*f*X, (k:常数, f: 频率, X:磁通), 所以当f由50-->60Hz时, X会相应减小

And E = k*f*X, (k: constant, f: frequency, X: flux), so when f is 50-->60Hz, X will decrease accordingly


对于电机来说, T=K*I*X, (K:常数, I:电流, X:磁通), 因此转矩T会跟着磁通X减小而减小.

For the motor, T=K*I*X, (K: constant, I: current, X: flux), the torque T decreases with the decrease of the flux X


同时, 小于50Hz时, 由于I*R很小, 所以U/f=E/f不变时, 磁通(X)为常数. 转矩T和电流成正比. 这也就是为什么通常用变频器的过流能力来描述其过载(转矩)能力. 并称为恒转矩调速(额定电流不变-->最大转矩不变)

At the same time, less than 50Hz, because I*R is very small, so the U/f=E/f at constant flux (X) is a constant torque and current is proportional to T. This is why usually used to describe the flow capacity of the inverter (torque) and overload ability. Called constant torque speed (rated current maximum torque constant -- > unchanged)


结论: 当变频器输出频率从50Hz以上增加时, 电机的输出转矩会减小.

Conclusion: when the output frequency of the inverter increases from 50Hz, the output torque of the motor will decrease


5. 其他和输出转矩有关的因素

5. other factors related to output torque


发热和散热能力决定变频器的输出电流能力,从而影响变频器的输出转矩能力。

Heating and cooling capacity determine the output current capacity of the inverter, thus affecting the output torque capacity of the inverter.


载波频率:一般变频器所标的额定电流都是以最高载波频率, 最高环境温度下能保证持续输出的数值. 降低载波频率, 电机的电流不会受到影响。但元器件的发热会减小。

Carrier frequency: the rated current of the general frequency converter is the highest carrier frequency, the maximum environmental temperature can guarantee the value of continuous output. Reduce the carrier frequency, the motor current will not be affected. But the heating of components will decrease.


环境温度:就象不会因为检测到周围温度比较低时就增大变频器保护电流值.

Ambient temperature: just like, it doesn't increase the protection current value of the transducer because of the low temperature around it


海拔高度:海拔高度增加, 对散热和绝缘性能都有影响.一般1000m以下可以不考虑. 以上每1000米降容5%就可以了 。

Altitude: elevation increases, has an impact on the heat dissipation and insulation performance. General 1000m below can not be considered. The above 1000 meters drop capacity 5% can be.


下一篇:没有了