# Electrical Drives

## Transient Performance of Stepping Motors

Transient Performance of Stepping Motors Step Response It was pointed out earlier that the single-step response is similar to that of a damped second-order system. We can easily estimate the natural frequency ωn in rad/s from the equation Knowing ωn, we can judge what the oscillatory part of the response will look like, by assuming …

## Drive Circuits and Pull Out Torque Speed Curves

Drive Circuits and Pull Out Torque Speed Curves Users often find difficulty in coming to terms with the fact that the running performance of a stepping motor depends so heavily on the type of drive circuit being used. It is therefore important to emphasise that in order to meet a specification, it will always be …

## Characteristics of Stepping Motors

Characteristics of Stepping Motors Static Torque–Displacement Curves From the discussion in previous article, it should be clear that the shape of the torque–displacement curve, and in particular the peak static torque, will depend on the internal electromagnetic design of the rotor. In particular the shapes of the rotor and stator teeth, and the disposition of …

## Stepping Motor

Stepping motors are attractive because they can be controlled directly by computers or microcontrollers. Their unique feature is that the output shaft rotates in a series of discrete angular intervals, or steps, one step being taken each time a command pulse is received. When a definite number of pulses has been supplied, the shaft will …

## Switched Reluctance Motor Drives

Switched Reluctance Motor Drives The switched reluctance drive was developed in the 1980s to offer advantages in terms of efficiency, power per unit weight and volume, robustness and operational flexibility. The motor and its associated power-electronic drive must be designed as an integrated package, and optimised for a particular specification, e.g. for maximum overall efficiency …

## Operation of Synchronous Motor Drives

Operation of Synchronous Motor Drives As soon as variable-frequency inverters became a practicable proposition it was natural to use them to supply synchronous motors, thereby freeing the latter from the fixed-speed constraint imposed by mains-frequency operation and opening up the possibility of a simple open-loop controlled speed drive. The obvious advantage over the inverter-fed induction …

## Synchronous Motors

Synchronous motors provide a precise, specific and constant speed for a wide range of loads, and are therefore used in preference to induction motors when constant speed operation is essential. Such machines are available over a very wide range from tiny single-phase versions in domestic timers to multi-megawatt machines in large industrial applications such as …

## Development of Induction Motor Equivalent Circuit

Development of Induction Motor Equivalent Circuit Physically, the construction of the wound-rotor induction motor has striking similarities with that of the 3-phase transformer, with the stator and rotor windings corresponding to the primary and secondary windings of a transformer. In the light of these similarities, it is not surprising that the induction motor equivalent circuit …

## Equivalent Circuit of Real Transformer

Equivalent Circuit of Real Transformer We turn now to the real transformer, with the aim of developing its equivalent circuit. Real transformers behave much like ideal ones (except in very small sizes), and the approach is therefore to extend the model of the real transformer to allow for the imperfections of the real one. For …

## Ideal Transformer

Ideal Transformer Because we are dealing with balanced 3-phase motors we can achieve considerable simplification by developing single-phase models, it being understood that any calculations using the equivalent circuit (e.g. torque or power) will yield ‘per phase’ values which will be multiplied by three to give the total torque or power. A quasi-circuit model of …