What is series-parallel control?
Here two identical motors are coupled together mechanically to a common load. Two speeds at constant torque are possible in this method one by connecting the motors armatures in series and the other by connecting them in parallel as shown in Fig. Thus armature control of speed is achieved. …
What is series-parallel control of DC locomotive?
Most DC motor circuits are arranged to control two or four motors. The control range is enhanced by changing the connections to the motors as the train accelerates. The system is known as “series-parallel control”. The diagram shows the resistors and contactors used to regulate the voltage across the motors.
How are DC series motors controlled?
Speed adjustment of a DC series motor by armature control may be done by:
- Armature Resistance Control Method.
- Shunted Armature Control Method.
- Armature Terminal Voltage Control.
What is the efficiency when two DC series motors are operated on series-parallel starting in traction locomotive?
Advantages of Series-Parallel Starting: 66.67% with two motors, 72.72% with four motors and 75% with six motors whereas only 50% efficiency is obtained with plain rheostat starting.
Why dc series motor is suitable for parallel operation?
If the series motors are connected in parallel, each and every armature of the motor receives the full normal voltage and hence the speed is also high. Thus we can achieve the two speeds (low or high) by connecting the motor either in series or parallel.
What are the electronic methods of speed control for DC motors?
Thus, the speed of a DC motor can control in three ways:
- By varying the flux, and by varying the current through field winding.
- By varying the armature voltage, and the armature resistance.
- Through the supply voltage.
Why DC series motor is suitable for parallel operation?
Where is DC series motor used?
Series DC motors are generally used where high starting torque is required, and speed variations are possible. These types of direct connection motors are, for instance, used in the traction system, cranes, air compressors, vacuum cleaners, sewing machines, etc.
What are the 3 ways of field control in DC series motor?
Thus, there are three general methods of speed control of D.C. Motors.
- Resistance variation in the armature circuit: This method is called armature resistance control or Rheostat control.
- Variation of field flux Ф This method is called field flux control.
- Variation of the applied voltage.
How do DC motors control speed?
Thus, the speed of a DC motor can control in three ways:
- By varying the flux, and by varying the current through field winding.
- By varying the armature voltage, and the armature resistance.
- Through the supply voltage.
What is DC series motor?
Series DC motors are a group of self-excited DC motors in which the field coil is connected in series to the armature winding and thus a higher current passes through it. A series DC motor mission is to turn the electrical energy into mechanical one based on electromagnetic law.
What are DC series motors used for?
How does parallel speed control of DC series motor work?
Further to increase the motor speed, then each motors are to be connected in parallel and the resistance to be connected in series at the same time. The starting resistance is again gradually reduced till full speed of the motor is achieved. At that moment field control is attained.
What is armature voltage control method in speed control of DC motors?
In the armature control method, the speed of the DC motor is directly proportional to the back emf (Eb) and Eb = V- IaRa. When supply voltage (V) and armature resistance Ra are kept constant, the Speed is directly proportional to armature current (Ia).
How does variable resistance affect DC series motor?
The speed of the DC series motor depends upon voltage drop across variable resistance. Higher the voltage drop across the armature, lower the speed. However there is considerable power loss in the variable resistance. This method is economical for constant torque drives. A variable resistor is connected across the armature in this method.
How are the field coils in a brushed DC motor connected?
The field coils have traditionally existed in four basic formats: separately excited (sepex), series -wound, shunt -wound, and a combination of the latter two; compound-wound. In a series wound motor, the field coils are connected electrically in series with the armature coils (via the brushes).
