In this era of magnifying innovation, even though the majority of us do not examine it in-depth, there are numerous details for which, even when we have a vague understanding, we can achieve greater productivity and efficiency. A capacitor is an example of a technological blessing that we can use in our daily lives. Numerous Higher Secondary students & engineers are familiar with this device capacitor and its applications.
The simplest way to explain it is that the capacitor serves as an additional stage in single-phase motors, such as the one that drives your fan. To generate magnetic torque, it divides the current into separate phases so that there is a sufficient phase difference between them.
To create net positive magnetic flux, it is necessary to place one capacitor on each single phase motor to do.
In the case of a capacitor, there is a complete change in magnetic flux for every current phase, resulting in net-zero magnetic fields for the whole current cycle. For the sake of keeping things simple and understandable, let’s start at the beginning.
Use of a capacitor
If you open the ceiling fan and take a look inside, you will see a small black box hidden inside the switch casing. It’s nothing more than a capacitor. This is a critical component of the fan that ensures that it operates properly. The capacitor is responsible not just for starting the fan, but also for making it spin. A simple explanation would be that when you turn on the fan, the capacitor generates a magnetic flux (torque).
The ceiling fan is typically powered by two capacitors connected in parallel series. The motor is referred to as a “two value capacitor run motor” or a “permanent split capacitor motor” depending on how it operates. In this case, a high-capacitance capacitor will be connected to the primary winding of a split-phase induction motor, and the motor will start. In the running winding, another capacitor with a low capacitance is employed.
In the case of a motor, what is the function of a capacitor, we might inquire. In other words, a motor equipped with either a begin or a run capacitor transforms into an electric capacitor that modulates the current flowing through numerous windings of a solitary alternating current induction motor. Magnetic torque is created as a result of this.
Function of Capacitor
A ceiling fan cannot be started with a single-phase alternating current supply, but what miracle does a capacitor perform in these engines to cause them to self-start?
According to the double field rotating theory, an alternate flux can be separated into two fluxes, each of which rotates in the opposing direction at the beginning of its rotation. Let’s break down the complicated circumstance into its simplest terms: a single-phase electric motor can be started by connecting an auxiliary winding or a capacitor in series with the main winding. See how it operates with the aid of a capacitor to see how it is done.
To start a single-phase alternating current induction motor, two stages are required to generate the spinning magnetomotive force (MMF), but we only have one phase available due to the single-phase alternating current supply in our houses. Consequently, an additional phase is required to start these types of motors properly. When we connect a capacitor with the beginning wind of a fan motor, we can achieve the second phase.
We also know that in a purely resistive circuit, the voltage and the current are in phase (i.e., they have the same phase). Capacitive and inductive circuits, on the other hand, do not behave in this manner.
In other words, in a perfect inductive circuit, the current lags 90 degrees behind voltage (or the voltage trails 90 degrees behind the current), whereas in a purely capacitive circuit, the current trails 90 degrees behind voltage (or the voltage trails 90 degrees behind the current). It is possible to produce phase angle in circuitry by using a combination of capacitor and inductor in this manner.
Value of a capacitor
To accomplish this, we connect the capacitor in series to a blowing wind. Because of the inductors & capacitors in this circuit, the following occurs when the circuit is turned on:
Due to inductance, current leads voltage by 45 degrees (or volts lag 45 degrees behind the flow) in the primary winding (or vice versa).
By capacitance, the running winding has a current that lags 45 degrees behind the flow (or a voltage that leads by 45 degrees from the current).
Running winding has sufficient resistance, resulting in the circuit being classified as a resistive–inductive circuit, with the resulting alternating current resistance being referred to as Inductive reactance (XL). The beginning winding has a high resistance and a low inductive reactance, resulting in an alternating current resistance that is equal to the reactance of the circuit (XC).
Thus, the resulting current flowing is 90 degrees out of phase with the input current. It means that we have two separate alternating phases, which results in the generation of rotating magnetic fields, and the torque generated causes the rotor to begin rotating.
The power source to the beginning winding is disconnected when the motor reaches 70 percent of its maximum speed, which is achieved via a centrifugal switch (Auxiliary winding). Capacitor start motors are the name given to this type of motor.
As a result of the expensive cost of capacitor motors, and the need for regular maintenance, a fixed rated capacitor (usually 2.5F to 3.5F) is permanently installed in the motor to overcome this problem.
Due to the modest size of the beginning wind, which only contributes to the production of the phase-shifting (low torque) required to begin the motor, capacitor start engines are not accessible in significant quantities.
Take note that if you link a capacitor in series to the primary winding instead of the initial blow, the fan blades would rotate in a reverse way from what you intended.