When load increases on shunt DC motor, the speed decreases resulting in a downfall in back-EMF. This in turn, causes the net voltage, and hence the current to increase causing an increase in torque and thereby increasing the speed. Thus, it achieves a constant speed.
Why does a DC compound motor have a higher speed regulation than a DC shunt motor?
When a load is applied, the increasing current through the series winding increases the field flux. As a result, the torque for a given current is greater than it would be for a shunt motor. However, this flux increase causes the speed to decrease to a lower value than in a shunt motor.
What factor determines the speed regulation of a DC motor?
The speed regulation of a DC motor is proportional to the resistance of the armature. The lower the armature resistance the better the speed regulation. The reason for this is that armature current determines the torque produced by motor if field excitation remains constant.
Why is DC series motor highly variable speed motor?
From speed-current characteristic curve it is obvious that the series motor is a variable speed motor i.e., speed varies with the variation in line current. … This is the reason that series motors are never started on no load. To start a dc series motor, mechanical load is first put and then the motor is started.
Why is speed regulation An important consideration with DC motors?
The speed regulation of a series motor is inherently poorer than that of a shunt motor. If the load on the motor is reduced the current flowing in both the armature and the field circuits is reduced causing a reduction in their flux densities.
Which DC motor is preferred for constant speed?
Explanation: Rotary compressor generally demand constant speed operation throughout the load. Sometimes, DC machines are not able to produce constant speed throughout the process hence, synchronous machine is used. 4.
How can the speed of a DC motor be controlled?
Thus, the speed of a DC motor can be controlled in three ways: By varying the supply voltage. By varying the flux, and by varying the current through the field winding. By varying the armature voltage, and by varying the armature resistance.
What is the speed equation of DC motor?
To derive the speed of a DC motor, we start with the equation for the DC motor’s EMF (Electromagnetic Force). We know that the EMF equation of DC motor is equal to: Hence rearranging the equation: N = 60A E / PZØ
Can DC motor run on AC supply?
We already know that in a DC Series motor the field winding has very less resistance than a DC Shunt Motor as the field is connected in series with the Armature Winding. So if we give AC supply on a DC Series Motor it will run perfectly. In fact, DC Series can run on both AC and DC supply.
Why Interpoles are used in DC machine?
Inter poles in dc machines help to reduce armature reaction effects in the inter polar regions and their windings are connected in series with the armature so that its effect can vary with the armature current.
What is the ideal no load speed for a series DC motor?
Explanation: At no load, armature current tends to zero, flux φ tends to zero, where speed is inversely proportional to the flux, speed will tend to infinity. Thus, no load speed of DC series motor is highest.
What are the advantages of DC series motor?
Advantages of DC Series Motor
- Dc series motor have good accelerating torque.
- Dc series motor have a relatively huge starting torques.
- Dc series motor delivers high torque during an overload.
- The dc series motor draws less current and power from the source compared to a shunt or compound motor.
What is the principle of dc series motor?
A DC motor is an electrical machine which converts electrical energy into mechanical energy. The basic working principle of the DC motor is that whenever a current carrying conductor places in the magnetic field, it experiences a mechanical force.
Which type of DC motor has a poor speed control?
Which of the following DC motor has the poorest speed control? Explanation: DC series motor at no load condition gives infinite speed ideally. Practically it will damage all the armature circuit. Thus, as the load is reduced speed of the motor will go on increasing rapidly.
How can we increase the rpm of dc motor?
By increasing the voltage of the armature, it produces more magnetic forces to overcome the field magnet, increasing the rpm. By increasing the field current, more magnetic fields opposing the motion are produced, at the same time more cemf is produced reducing the armature voltage, decreasing the rpm.