5SHY3545L0014 3BHB013085R0001 ABB 3BHE039203R0101 GVC736CE101 直流调速中压板

二、直流电动机的调速特点

1 、降低电枢电压调速，电枢回路必须有可调压的直流电源，电枢回路及励磁回路电阻尽可能小，电压降低转速下降，人为特性硬度不变、运行转速稳定，可无级调速。改变电枢电压主要是从额定电压往下降低电枢电压，从电动机额定转速向下变速，属恒转矩调速方法。对于要求在一定范围内无级平滑调速的系统来说，这种方法最好。电枢电流变化遇到的时间常数较小，能快速响应，但是需要大容量可调直流电源。

2 、电枢回路串电阻调速，人为特性是一簇过理想空载点的射线，串电阻越大，机械特性越软、转速越不稳定，低速时串电阻大，损耗能量也越多，效率变低。调速范围受负载大小影响，负载大调速范围广，轻载调速范围小。在电动机电枢回路外串电阻进行调速的方法，设备简单，操作方便。但是只能有级调速，调速平滑性差，机械特性较软;在调速电阻上消耗大量电能。改变电阻调速缺点很多，目前很少采用。

3 、弱磁调速，一般直流电动机，为避免磁路过饱和只能弱磁不能强磁。电枢电压保持额定值，电枢回路串接电阻减至最小，增加励磁回路电阻 Rf ，励磁电流和磁通减小，电动机转速随即升高，机械特性变软。改变磁通可以以实现无级平滑调速，但只能减弱磁通，从电动机额定转速向上调速、属恒功率调速方法。电枢电流变化时遇到的时间常数要大很多，响应速度较慢．但所需电源容量小。

注意：转速升高时，如负载转矩仍为额定值，则电动机功率将超过额定功率，电动机过载运行、这是不允许的，所以弱磁调速时，随着电动机转速的升高，负载转矩相应减小，属恒功率调速。 为避免电动机转子绕组受离心力过大而撤开损坏，弱磁调速时应注意电动机转速不超过允许限度。

3、改变电枢的电刷接入位置

改变电枢绕组与励磁绕组的偏移角来改变直流电机的放置方向。

另外，他励和并励直流电动机一般采用电枢反接法来实现正反转。他励和并励直流电动机不宜采用励磁绕组反接法实现正反转的原因是因为励磁绕组匝数较多，电感量较大。当励磁绕组反接时，在励磁绕组中便会产生很大的感生电动势．这将会损坏闸刀和励磁绕组的绝缘。

5SHY3545L0014 3BHE023784R0001

Second, the speed regulation characteristics of DC motor

1, reduce the armature voltage speed regulation, the armature circuit must have adjustable voltage DC power supply, the armature circuit and excitation circuit resistance as small as possible, the voltage is reduced, the speed is decreased, the hardness of artificial characteristics is unchanged, the running speed is stable, and the speed can be stepless. Changing the armature voltage is mainly to reduce the armature voltage from the rated voltage, and change the armature voltage from the rated speed of the motor, which is a constant torque speed regulation method. This method is best for systems that require stepless smooth speed regulation within a certain range. Armature current changes encounter a small time constant, can respond quickly, but requires a large capacity of adjustable DC power supply.

2, the armature circuit series resistance speed regulation, artificial characteristics is a cluster of rays over the ideal no-load point, the greater the series resistance, the softer the mechanical characteristics, the more unstable the speed, the lower the low speed series resistance, the more energy loss, the lower the efficiency. The speed regulation range is affected by the load size, and the speed regulation range is wide with large load and small with light load. The method of speed regulation in the external series resistance of the armature circuit of the motor is simple and easy to operate. However, there can only be stage speed regulation, the smoothness of speed regulation is poor, and the mechanical characteristics are soft; A large amount of electrical energy is consumed on the governor resistance. There are many disadvantages of changing resistance speed regulation, which is rarely used at present.

3, weak magnetic speed regulation, general DC motor, in order to avoid magnetic circuit supersaturation can only weak magnetic can not strong magnetic. The armature voltage is maintained at the rated value, the armature circuit series resistance is reduced to the minimum, the excitation circuit resistance Rf is increased, the excitation current and magnetic flux are reduced, the motor speed is then increased, and the mechanical characteristics become soft. Changing the flux can achieve stepless smooth speed regulation, but it can only weaken the flux, and speed up from the rated speed of the motor, which is a constant power speed regulation method. The time constant encountered when the armature current changes is much larger, and the response speed is slower. However, the power capacity required is small.

Note: When the speed increases, if the load torque is still the rated value, the motor power will exceed the rated power, the motor overload operation, which is not allowed, so the weak magnetic speed regulation, as the motor speed increases, the load torque decreases accordingly, which is a constant power speed regulation. In order to prevent the motor rotor winding from being damaged by excessive centrifugal force, it should be noted that the motor speed should not exceed the allowable limit when the weak magnetic speed regulation.

3, change the armature brush access position

Change the offset Angle between armature winding and excitation winding to change the direction of DC motor.

In addition, separately excited and shunt excited DC motors generally use armature reverse connection to achieve positive and negative rotation. The reason why the field winding reverse connection method is not suitable for the separately excited and shunt excited DC motor is that the number of turns of the field winding is large and the inductance is large. When the field winding is reversed, a large induced electromotive force will be generated in the field winding. This will damage the insulation of the knife and the excitation windings.