Tag: electrical machines
-
Common Causes of Failures of Power Transformers
As with most of electrical equipment, the key causes of failure of power transformers are either due to electrical failure or mechanical failure. These failures don’t occur that often as compared with other failures in other electrical equipment like switchgear. Common failures of power transformers and their causes are discussed in the following sections. Typical…
-
Phase Locked Loop High Precision Motor Speed Control System
AC generators can be utilized in high precision control systems. The AC generator rotor is rotated by the rotating shaft (i.e. the shaft from the motor being controlled). The output AC frequency is proportional to shaft speed. Zero crossings per time interval can be counted to determine speed for a simple control system. If high…
-
How to Wire an Industrial Control Motor
Option 1: With a Toggle Switch Let’s consider a simple three-phase, 480V AC motor control circuit consisting of a contactor, overload block, control power transformer, power fuses or (you may use circuit breakers) and the associated components as illustrated in the figures below: The schematic diagram for the same circuit is shown below: The control…
-
How to Perform a Brake Test on a DC Motor
Testing is usually performed on DC machines to establish efficiency and power losses. A brake test is a direct technique that involves applying a brake to a water-cooled pulley mounted on the motor shaft as demonstrated in Figure 1.0. This brake test method is typically used on small motors. The brake band is fixed with…
-
Features and Applications of Instrument Transformers
Instrument transformers are used in the measurement of voltage, current, energy, and power in ac circuits. The main reasons why instrument transformers are employed in measurements are: In power systems, the levels of currents and voltages handled are very high, and therefore direct measurements with conventional instruments is not possible without compromising the operator safety,…
-
What is the difference between a Power transformer and a Distribution Transformer?
Introduction The transformer, in simple terms can be defined as the voltage regulator. It helps in stepping up and stepping down of the voltages. We all have seen transformers in our locality, where the current is passed from higher voltage to the lower voltages. In this blog, we will discuss about the differences between the…
-
Speed Control of a DC Compound Motor
A compound motor is a combination of a series and a shunt-wound motor. The Speed-torque characteristics for a compound motor Speed Control of a DC Compound Motor Speed is controlled by variable resistors in the shunt field and armature circuit. The series winding may be arranged that it aids the shunt field (cumulative compound) or…
-
DC Shunt Motor Speed Control
In the shunt motor, the motor winding is in parallel with the armature. From the figure above, the supply current I = Ia + If . Unlike a series motor, if the load is removed from the motor, only the armature current will decrease, the field remaining at the same strength. Therefore the motor will…
-
Speed Control of a DC Series Motor
The dc series motor has its windings and armature connected in series across the supply. From the figure above, the armature current Ia also supplies the field, hence when Ia is large on starting for example, the magnetic field will be strong, and the torque will be high. As the machine accelerates, the torque, armature…
-
The Essential Components of An Electric Drive
Power electronics deals with the applications of solid-state electronics for the control and conversion of electric power. The conversion techniques require switching power semiconductor devices ON and OFF. The block diagram below shows the essential components of an electric drive controlled by a power semiconductor converter. The converter regulates the flow of power from the…