Coordinates regulation of AM by resistors in stator circuit

The method allows to regulate AM coordinates due to additional resistors in the stator circuit. It is better to use such method for AM with short-circuited rotor, for which it is impossible using of any regulating devices in the rotor circuit. The scheme (fragment а on figure 4.26) and characteristics (fragment b on figure 4.26) correspond to this method.

The speed regulation by this method is inefficient, the range of speed regulation is small, regulation is uneconomical, the rigidity of characteristics is not constant, overload capability is not constant too and decreases with the increasing of resistance .

The features of mechanical characteristics (see fragment b on figure 4.26):

- speed of ideal idling rate does not depend on the resistance ;

- maximal moment of motor decreases with the resistance increasing ;

- starting moment decreases with the resistance increasing ;

- rigidity of characteristics decreases with the resistance increasing .

а – scheme;

b – characteristics.

Figure 4.26 – Method of regulation with resistor in stator circuit.

Taking into account the abovementioned, the regulation by this method is seldom used and only for AM with short-circuited rotor, when the alternative of regulation methods is limited.

This method is used often for regulation of another coordinates such as current and moment of AM with short-circuited rotor, for its limiting in transient processes at starting, reverse and braking, for example, in two-speed ED of elevators at transition from the high speed to low one. At that, in the stator circuit a resistor is connected to only one phase. It has a small influence on motor characteristics, but the scheme is simplified essentially.

Дата добавления: 2014-01-05