12 Pulse vs. Six Pulse

Attribute	12 Pulse	Six Pulse
Number of pulses	12	6
Phase shifting	Yes	Yes
Harmonic distortion	Lower	Higher
Output voltage ripple	Lower	Higher
Transformer size	Smaller	Larger

Introduction

When it comes to power electronics, pulse width modulation (PWM) techniques are commonly used to control the output voltage of inverters. Two popular PWM techniques are 12 pulse and six pulse. In this article, we will compare the attributes of these two techniques to understand their differences and applications.

Number of Pulses

The most obvious difference between 12 pulse and six pulse PWM techniques is the number of pulses used in the modulation. As the names suggest, 12 pulse uses 12 pulses while six pulse uses only six pulses. This difference in the number of pulses has a significant impact on the performance and characteristics of the PWM technique.

Harmonic Distortion

One of the key differences between 12 pulse and six pulse PWM techniques is the level of harmonic distortion in the output voltage. Due to the higher number of pulses in 12 pulse modulation, it typically has lower harmonic distortion compared to six pulse modulation. This makes 12 pulse PWM more suitable for applications where low harmonic distortion is critical, such as in power quality sensitive environments.

Input Current Ripple

Another important attribute to consider when comparing 12 pulse and six pulse PWM techniques is the input current ripple. The higher number of pulses in 12 pulse modulation results in lower input current ripple compared to six pulse modulation. This can be advantageous in applications where minimizing input current ripple is important, such as in motor drives or renewable energy systems.

Output Voltage Quality

When it comes to the quality of the output voltage, 12 pulse PWM typically provides a smoother and more sinusoidal output voltage compared to six pulse PWM. This is due to the higher number of pulses in 12 pulse modulation, which allows for better voltage control and regulation. As a result, 12 pulse PWM is often preferred in applications where high-quality output voltage is required.

Efficiency

Efficiency is another important attribute to consider when comparing 12 pulse and six pulse PWM techniques. In general, 12 pulse PWM tends to be more efficient than six pulse PWM due to its lower harmonic distortion and input current ripple. This can result in lower losses and higher overall efficiency in power electronic systems utilizing 12 pulse modulation.

Cost

Cost is also a factor to consider when choosing between 12 pulse and six pulse PWM techniques. In general, 12 pulse modulation tends to be more complex and expensive to implement compared to six pulse modulation. The additional components and circuitry required for 12 pulse modulation can increase the overall cost of the system, making six pulse modulation a more cost-effective option in some applications.

Applications

Both 12 pulse and six pulse PWM techniques have their own set of applications where they are best suited. 12 pulse PWM is often used in high-power applications where low harmonic distortion and high-quality output voltage are critical, such as in industrial motor drives and grid-tied inverters. On the other hand, six pulse PWM is commonly used in medium-power applications where cost-effectiveness and simplicity are more important, such as in consumer electronics and small motor drives.

Conclusion

In conclusion, the choice between 12 pulse and six pulse PWM techniques depends on the specific requirements of the application. While 12 pulse PWM offers lower harmonic distortion, smoother output voltage, and higher efficiency, it comes at a higher cost and complexity. On the other hand, six pulse PWM is more cost-effective and simpler to implement, but may not provide the same level of performance in terms of harmonic distortion and output voltage quality. Ultimately, the decision should be based on a careful evaluation of the application's needs and priorities.