In this lesson aspects of starting and speed control of d.c motors are D.C shunt, (ii) separately excited and (iii) series motor widely used are given at the. The equivalent circuit for a series dc motor is shown in Figure In a series dc motor, the armature current, the field current, and the line current are all the. DC Series Motor Used as a Universal Motor. The series motor provides high starting torque and is able to move very large shaft loads when it is first energized .
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DC motors consist of one set of coils, called armature winding, inside another set of coils or a set A winding is made up of series or parallel connection of coils. Characteristics of DC Series bestthing.info - Download as PDF File .pdf), Text File . txt) or read online. Types of DC Motors. • Separately Excited Motor. • Shunt Excited Motor. • Series Excited Motor. • Compound Excited Motor. • Permanent Magnet (PM) Motor.
PLC simulation of overload and over speed protections Fig.
Overload protection. Over speed protection. These protections are implemented successfully by the analog comparator functions which compare the maximum values of Ia, If and N setting values with the measured ones by the sensors and operates when they exceed these setting values. It displays also warning massages, flashing signals, date and times of operations and bar curves .
Separately Excited DC Motor
The program of the PLC is illustrated by the following flowchart in Fig. Flowchart of main program Hassaan T. Qasim 2. Schematic diagram of the experimental setup It consists mainly of: 1. DC series motor whose technical specifications [7, 8] are shown in Table 1.
Table 1. DC generator coupled with the DC motor to apply the mechanical load. Hall effect sensors [9, 10].
Speed encoder . Our experiment had been applied by a machine laboratory unit equipped with a PLC basic unit, its extension modules and an HMI. This unit was constructed in our institute by the team of machines laboratory as shown in Fig.
Types of DC Motor
Kufa Journal of Engineering, Vol. The laboratory unit As shown in Fig. Display output HMI Fig. The traditional laboratory unit Hassaan T. Qasim 3.
Shaft torque of motor in N. Speed of motor in rpm 3. Percentage efficiency of motor 4.
Output power of motor in KW Figs. W Fig. It shows that the efficiency of the motor increases in case of PLC system. The increasing values in the torque, output power and efficiency of the motor when implementing the PLC system are due to the decreament in the mechanical losses which are avialable in the traditional mechanical system for measuring the torque of the series DC motor. Thus the motor starts rotating at its maximum speed in the beginning.
The rotating armature in the presence of the magnetic field results in counter EMF, which limits the current build up in the series combination of armature and winding.
Thus series motors once started will offer maximum speed and torque but gradually, with an increase in speed, its torque will come down because of its reduced current. Practically this is what required from the motors. Due to the high torque provided by the armature, the load on the shaft is set to rotate initially.
Characteristics of DC motors
Subsequently lesser torque will keep the load on the move. This further helps in increasing the heat dissipation of the motor.
However, the amount of torque generated by motor is directly proportional to the winding current. The higher current demands a higher power supply, too.
In DC series motors, a linear relationship exists between the amount of torque produced and the current flowing through the field windings. The speed of the motor can be controlled by varying the voltage across the motor, which further controls the torque of motor.
To increase the speed of the motor, decrease the field current by placing a small resistance in parallel to the winding and armature. To decrease the speed, use an external series resistance along with the field winding and armature.
This will reduce the voltage across the armature with the same counter EMF, thus resulting in a lower speed of motor. To increase the speed of the motor, decrease the field current by placing a small resistance in parallel to the winding and armature. To decrease the speed, use an external series resistance along with the field winding and armature. This will reduce the voltage across the armature with the same counter EMF, thus resulting in a lower speed of motor.
Unlike DC shunt motors , series motor does not operate at the constant speed. The speed of the motor varies with change in the shaft load, so speed control of the motor is not easy to put into practice.
Applications, Advantages and Precautions Series motors can produce large turning effect, or torque, from a stand still. These motors have found application in small electrical appliances where high torque is necessary at start up. DC series motors are used mainly for industrial applications, e. Heavy and magnificent cranes drawing thousands of amperes are driven by this motor.
An automobile engine can be started by this motor which draws around A of current. However, these motors are not suitable where constant speed is required as the speed of series motors is dependent varies with load on load unlike DC shunt motors see link below for an article similar to this one that covers DC shunt motors whose speed is independent of load.
The construction, designing, and maintenance of these motors is very easy. Series motors are cost effective as well.Speed of motor in rpm 3.
Construction and Principle of Operation of DC Series Motor
The speed of the motor varies with change in the shaft load, so speed control of the motor is not easy to put into practice. As we know, flux is directly proportional to Ia, speed is inversely proportional to Ia.
T - the torque applied to the rotor by an external load N. For DC series motor, the field coil and armature windings are connected in series to the power source.