The electric motors of various designs are available to meet the needs of various classes of industry. So the selection of electric motor itself has become an important and tedious process. The conditions under which an electric motor has to operate and the type of load it has to handle, determine its selection. The various factors that are to be [...]
In this article we will discuss about the single and four quadrant operation of electric motors. Single Quadrant Operation of Electric Motors: Single quadrant operation means that load and the motor shall be required to run only in one specified direction under the action of developed torque. When an electric motor is switched to electric supply mains and drives mechanical [...]
For selection of reliable and efficient motor it is essential that the conditions of service are well known. It is not sufficient to simply specify the output power in kW and the speed but it is also necessary to know the following additional particulars: (i) Torque at the shaft during running, starting and at different loads. (ii) Accelerating torque and [...]
In this article we will discuss about the characteristics and performance curves of a dc series motor. Characteristics of a DC Series Motors: 1. Speed-Current Characteristic: In case of a dc series motor, the mmf due to the exciting coils increases in direct proportion to the line or armature current, so (neglecting armature reaction effects) the value of flux varies [...]
In this article we will discuss about the characteristics and performance curves of dc shunt motors. Characteristics of a DC Shunt Motor: 1. Speed-Armature Current Characteristic: If applied voltage V is kept constant, the field current will remain constant, hence flux will have maximum value on no load but will slightly decrease due to armature reaction as the load increases [...]
Here is a list of three-phase ac motors: 1. Three-Phase Induction Motors 2. Three-Phase Synchronous Motors 3. Synchronous Induction Motors 4. Variable Speed Commutator Type 3-Phase Induction Motor 5. Compensated Induction Motor 6. Three-Phase AC Series Commutator Motor 7. Three-Phase AC Shunt Commutator Motor. 1. Three-Phase Induction Motors: 3-phase induction motors have gained extremely wide application in industry by virtue [...]
Single-phase motors are more widely used than 3-phase motors because of two following basic reasons: First for reasons of economy, most houses, offices and also rural areas are supplied with single-phase ac and the second factor is the economics of the motor and its branch circuit. Fixed loads requiring not more than 0.5 kW can generally be served most economically [...]
The following points highlight the five main types of split-phase motors. The types are: 1. Resistance-Start Single-Phase Induction Motor 2. Capacitor-Start Single-Phase Induction Motor 3. Capacitor-Start Capacitor-Run Single-Phase Induction Motor 4. Permanent Capacitor Single Phase Induction Motor 5. Shaded-Pole Motor. Type # 1. Resistance-Start Single-Phase Induction Motor: It is a form of split-phase motor having a high resistance connected in [...]
Solid state devices find more and more applications in industry and, therefore, it becomes imperative to have preliminary knowledge of such devices. The main devices usually used for motor control are diode, thyristor or silicon controlled rectifier, triac, diac, power transistors etc. Every device has certain maximum voltage, current and time response (speed) capabilities. These can very rarely be achieved [...]
Motor control devices may be classified as primary control devices and pilot control devices. Pilot devices control the primary control devices which in turn controls (connects or disconnects) the motor or load. For example in D-O-L (direct- on-line) starter main contactors and triple pole switch, which connect the motor to the line are classified as primary control devices whereas start [...]