CHARACTERISTICS OF ELECTRIC MOTORS

Methods of Starting Electric Motor

Methods of Starting Electric Motor: Methods of Starting Electric Motor – Transient processes involved with the starting of the (drive) motor in a variable speed drive require a detailed study. The electric motor and connected load accelerates to the rated speed from rest under the influence of the starting torque. The transient operation during  is […]

Braking of Synchronous Motor

Braking of Synchronous Motor: The methods that are employed for Braking of Synchronous Motor are: Regenerative braking while operating on a variable frequency supply Rheostatic braking Plugging Regenerative braking When the motor operates as a variable speed drive motor utilizing a variable frequency supply, it can be regeneratively braked and all the K.E. returned to […]

Braking of Induction Motor

Braking of Induction Motor: The three types of Braking of Induction Motor, namely regenerative, dynamic and counter current braking can be accomplished with induction motors also. Regenerative braking When the rotor of an induction motor runs faster than the stator field the slip becomes negative and the machine generates power. Therefore, whenever the motor has […]

DC Motor Electric Brakes

DC Motor Electric Brakes: DC Motor Electric Brakes – While operating electrical drives it is often necessary to stop the motor quickly and also reverse it. In applications like cranes or hoists the torque of the drive motor may have to be controlled so that the load does not have any undesir­able acceleration, e.g. in […]

Characteristics of Synchronous Motor

Characteristics of Synchronous Motor: Characteristics of Synchronous Motor are constant speed motors. The speed of the motor is decided by the number of poles and frequency. Compared to an induction motor, it is very sensitive to sudden changes of load. This causes a hunting of the rotor and finally leads to stability problems. It has […]

Speed Torque Characteristics of Induction Motor

Speed Torque Characteristics of Induction Motor: Speed Torque Characteristics of Induction Motor – From Eq. 1.27 it can be observed that the maximum torque is independent of rotor resistance. However, the slip at which the maximum torque occurs changes with rotor resistance. When the rotor resistance is increased, so is the slip for maximum torque, […]

Characteristics of Three Phase Induction Motor

Characteristics of Three Phase Induction Motor: The performance Characteristics of Three Phase Induction Motor can be de­rived using the approximate equivalent circuit shown in Fig. 1.20(a). In the circuit The phasor diagram of the motor is shown in Fig. 1.20(b). In an induction motor the power transferred to the rotor (Pd), rotor copper loss (Pcu2) and […]

DC Motor Speed Control

DC Motor Speed Control: In the foregoing sections we discussed the torque-speed characteristics of dc motors, bringing out the effects of armature voltage variation and field current on them. The discussion also applies to the study of the methods of DC Motor Speed Control, which may be summarised as follows: Variation of armature voltage by […]

Speed Torque Characteristics of DC Compound Motor

Speed Torque Characteristics of DC Compound Motor: A schematic of a Speed Torque Characteristics of DC Compound Motor is shown in Fig. 1.18. There are both series and shunt fields (separately excited fields). The orientation of the series flux may be such as to aid or oppose the shunt flux in the magnetic circuit. In […]

Speed Torque Characteristics of Series Motor

Speed Torque Characteristics of Series Motor: The field winding is connected in series with the armature (Fig. 1.2(b)). The armature current and field current are the same. The operating Speed Torque Characteristics of Series Motor may be deduced for a series motor in the same way as described before for shunt motor/separately excited motor using […]

Speed Torque Characteristic of DC Shunt Motor

Speed Torque Characteristic DC Shunt Motor: The preceding discussion shows that armature voltage variation gives creeping speeds. The simple rheostatic method provides a Speed Torque Characteristic DC Shunt Motor with little hardness and little stability. Ward Leonard control (smooth variation of voltage), on the other hand, produces a flat characteristic with reasonable hardness and stability, […]

Speed Torque Characteristic of Separately Excited DC Motor

Speed Torque Characteristic of Separately Excited DC Motor: The circuit equation of a Speed Torque Characteristic of Separately Excited DC Motor whose armature, having a total of Z con­ductors, is wound for 2P poles (the brushes divide the winding into 2a parallel paths), is Where E is the back emf of the armature given by […]

Characteristics of DC Motor

Characteristics of DC Motor: Characteristics of DC Motor are of the rotating armature type. The armature winding is a closed winding through the commutator. The armature is supplied through the brushes which are placed along the neutral axis on the commutator. The field system is stationary. The mmf produced by the field is along the […]

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