What factors limit the maximum speed of field control DC motor?

The above equation shows that the speed depends upon the supply voltage V, the armature circuit resistance Ra, and the field flux Ф, which is produced by the field current. In practice, the variation of these three factors is used for speed control.

What are the factors that affect the speed of a DC motor?

Factors Affecting The Speed Of A D.C. Motor

  • The flux Φ
  • The voltage across the armature.
  • The applied voltage V.

What are the factor that control motor speed?

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.

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How can you reduce the speed of a DC motor?

A couple of things you can do:

  1. Use gears to change ratio of speed, which is what you’re going to do. …
  2. Use a stepper motor, which are commonly used for high-torque, low RPM applications.
  3. Find some sort of PWM control circuit to slow it down, although you probably won’t be able to get it down to 5-10RPM.

What are the various limitations of field control methods of speed control of dc motor?

Disadvantages of field control include: Limits on speed: If your application requires you to adjust the motor below the normal speed, you may be better off choosing an armature controlled method. Field controlled DC motors can only operate above the normal speed. Higher speeds can also result in less torque.

What are the two factors controlling the speed of a DC motor?

Factors Affecting The Speed Of Dc Motor

  • The applied voltage.
  • The flux.
  • The voltage across an armature.


What are the two ways to increase the speed of a DC motor?

The speed of the motor can be increased by:

  • increasing the strength of the magnetic field.
  • increasing the current flowing through the coil.

How do you increase motor speed?

Increasing the speed can be achieved by increasing the supply frequency as the speed and frequency are directly proportional; however, there are two constraints. The first is the saturation of the magnetic circuit, but this issue can be significantly avoided by keeping the V/f ratio constant.

What is the speed of dc motor?

DC controls adjust speed by varying the voltage sent to the motor (this differs from AC motor controls which adjust the line frequency to the motor). Typical no load or synchronous speeds for an AC fractional horsepower motor are 1800 or 3600 rpm, and 1000-5000 rpm for DC fractional hp motors.

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How do you calculate the speed of a DC motor?

Speed of a DC Motor

A = number of parallel paths. Z = total no. conductors in armature. Hence, speed of a DC motor is directly proportional to emf of rotation (E) and inversely proportional to flux per pole (φ).

How long can a DC motor run continuously?

You should anticipate, given proper attendance, that the motor can run continuously for the life of its brushes, which should be in the range of six months to a year. Presuming that the motor is too small to have its brushes changed by a trained electrician while running.

Why is it necessary to control the speed of a DC motor?

DC Motors plays an important role in energy conversion process. It is a machine which converts electrical energy into mechanical energy. In mechanical system, speed varies with number of task so speed control is necessary to do mechanical work in a proper way. It makes motor to operate easily.

How does change in resistance affect the speed of a DC motor?

The speed of a permanent magnet DC motor is primarily determined by voltage. The problem with using a series resistor is that its voltage drop is proportional to current. If the motor draws constant current then the resistor will drop a constant voltage and the motor will run at a fixed (lower) speed.

Which is not a method of speed control of a dc motor?

Which of the following is not the method of speed control in DC series motor? Explanation: Diverter means adding a variable resistance in parallel with field winding. Tapped field control is the method where field ampere turns are adjusted in steps by varying the number of turns included in the circuit.

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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.