So which pwm technique is best

Being able to vary their speed with PWM increases the efficiency of the total system by quite a bit. PWM Pulsed Width Modulation reduce neither the voltage or current , it reduces the averaged voltage and current by changing the amount of on time compared to off time this force is applied which will reduce the average power but the instantaneous power is the product of the voltage x current.

Having a PWM, means you do not have a resistor in series,meaning no waste in the form of heat. So , no waste of power is there. In a conventional inverter the output voltage changes according to the changes in the load. To nullify effect caused by the changing loads, ….

The different PWM techniques are Single pulse width modulation, Multiple pulse width modulation, Phase displacement control, Sinusoidal pulse width modulation, Harmonic Injection modulation, Space Vector pulse width modulation, Hysteresis Delta pulse width modulation, Selective Harmonic Elimination and Current …. The speed of regular fans can be modified by voltage regulation. PWM on the other hand lets it rotate faster or slower , depending on the situation.

The mm fans are the standard fans in most PCs. They boast several impressive features, including noise levels many users would consider acceptable. With better noise levels and airflow, the mm would be more superior.

The third wire gives your computer a measure of control over that. Although the header pin layout looks similar, as OP has found one of the holes in the connector is blocked off so you can NOT plug it into a 4-pin header by mistake.

You use 3 pin fans for case fans. To determine if regeneration is occurring, we must look at the average value of bus current. If the average value is negative, then we have a long-term transference of energy from the load back to your DC supply. Words are good; pictures are great, but sometimes, you just have to see it for yourself to understand what is going on.

The best way to do this is on a lab bench where you roll up your shirtsleeves, grab an oscilloscope probe and have some fun! However, the next best way to understand this concept is to watch a simulation.

To that end, I have created a VisSim simulation showing two identical motors with identical loads, supplied with identical PWM values. You can access the simulation here. With the trial version, you have access to all the features, and you can even change the simulation topology to test other ideas if you wish. So go ahead and open the simulation and have some fun!

Adjust the PWM duty cycle to a large value, and let the motors ramp up to speed. Then quickly bring the duty cycle down toward zero. Motor 1 which utilizes a 2-quadrant PWM will coast down slowly. But Motor 2 which utilizes the 4-quadrant PWM we have just introduced will decelerate quickly. This is because regen is occurring on Motor 2, as indicated by the red regen light on its H-Bridge.

A screenshot of the simulation is shown below. Now try this: With the PWM still set to a positive value, change the load torque to be negative. If the motor is generating electrical power, you need to have some place for that power to go.

If your application is an electric vehicle coasting down a hill, the generated electrical energy can be put to good use by charging the batteries.

But if you have an electric drive which needs to stop its load abruptly, the resulting generator action can destroy the drive if there is no place to put the energy. Some PWM topologies will inherently prevent regeneration of energy back into your electrical supply.

In fact, some will only allow the motor to spin in one direction and generate torque in that same direction. These drives as you might expect are called single-quadrant drives and operate either in quadrant 1 or quadrant 3. A typical example of such a drive is shown below, where a PWM signal is applied to a single transistor.

These types of motor drives are common in applications where cost is critical, such as toys, electric baby swings, and so on.

The motor can only spin in one direction and generate torque in that same direction. If you try to decelerate the motor i.