Engineering 101

What’s DC Motor Control, Why Does It Matter, and How Can You Do It?


A DC motor is one of the most basic motors you can get, and it helps convert electrical energy to mechanical energy. DC motors are classified into three main sub-types: brushed motors, universal motors, and permanent magnet motors. These motors contain vital components that aid in their operation. A DC motor must contain an armature, stator and a commutator. The commutator should have brushes which assist in its processes.

The DC motor also possesses magnets that assist in its operations. The magnet can either be permanent or electromagnetic. An armature is placed between the North and South poles of the magnet. When electrical current passes through the coil or armature, it produces torque. The magnetic field or the permanent magnet is known as the stator. The motor has a commutator which allows for the current to flow through to the armature.

Importance of Speed Control In DC Motors

An unregulated DC motor speed can be challenging to achieve desired performances. It’s essential to control the speed of your DC motor so that you can get full performance capabilities of your tools. The precise speed ensures you don’t get tool chatter as you operate your devices.   At low speeds, one can get high torque, which is desirable for heavy duties. This means it’s capable of running things like conveyor belts, cranes or elevators. The size of a DC motor is small when compared to an AC motor and its capable of moving even at zero speeds. At high speeds, it can be used for applications like screw cutting or wood turning. The choice of the variable rates depends on the torque needed to run the task.

How Can You Speed Up a DC Motor?  

DC motor speed control is essential in achieving operational requirements. It helps vary the speed of your motor to satisfy different needs. DC motor control speed is useful in many industrial applications. It can control robotic vehicles or even the motors used on elevators.

There are some common ways in which you can alter the speed of a DC motor:  

  1. Flux Control Technique: The magnetic flux of any DC motor can be altered to vary the speed of a DC motor. The strength of magnetic flux is determined by the current flow passing through a field winding. To lower the amount of current passing through a variable resistor can be used. If the resistor is at its normal stated position, the speed of the DC motor is standard. Once the rate of resistance is increased, the rate or the current passing through to the armature decreases. As a result, the flux produced decreases. Therefore, the speed of the motor increases above its standard value.
  2. Armature Control Technique: DC motor speed can be controlled by altering the armature’s resistance and ability to regulate the voltage drop in the armature. A variable resistor is used on the armature but placed in a series connection. If the variable resistor is at its minimal value, then the armature’s resistance is at its normal state. The voltage on the armature also drops when the resistor is at its lowest value. If the value of the resistor increases, the voltage across the armature decreases. The drop in the current level lowers the speed of the motor gradually. The armature control technique helps in gaining low rates.

Voltage Control

Both armature control and Flux control will not offer desirable speed ranges. The flux method affects the motor’s commutation. The armature method, on the other hand, is significantly characterized by undesirable and significant power losses. The use of resistors on the armature also contributes to power loss. The voltage control mechanism allows the winding to receive a fixed amount of voltage, where the armature receives a variable amount of energy. The voltage control mechanisms use a gear mechanism that offers a variable voltage to the motor’s armature. Switchgear can be used with the voltage control technique to give the armature a variable voltage. An AC motor-driven generator can be used to provide the variable voltage.

Pulse width modulation is one of the commonly used technique to get desirable speeds. PWM works by varying the width pulses, which can control the voltage applied. The method lowers power loss and improves performance. It also uses less complicated devices hence a more straightforward construction.

If you are looking for means to increase the speed of a DC motor, you can use two techniques. The influx method lowers the influx on the motor and hence increase its speed; the voltage control method can also speed up the DC motor where necessary. You may prefer to use the voltage control mechanism is safer and better since its power saving and its construction is simple.

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