Abstract Pulse width modulation (PWM) AC drives can generate elevated differential mode voltages due to the reflected wave phenomenon, fast rise times and peak voltages. While many users are familiar with differential mode voltages, common mode voltages created by PWM inverters are less familiar. Problems associated with common mode voltages can include erratic behavior of… Read more »
Todd Shudarek, Principal Engineer – The proliferation of variable frequency drives (VFDs) has brought increased attention to harmonic effects created by drives. A standard 6-pulse drive with no harmonic mitigation technology may interfere with neighboring equipment, reduce equipment life, and negatively impact the utility power quality. Under some circumstances the total harmonic current distortion (THID)… Read more »
Todd Shudarek, Principle Engineer – The proliferation of variable frequency drives (VFDs) has brought increased attention to harmonic effects created by drives. A standard 6-pulse drive with no harmonic mitigation technology may interfere with neighboring equipment, reduce equipment life, and negatively impact the utility power quality. Under some circumstances the total harmonic current distortion (THID)… Read more »
As Variable Speed Drives (VFD’s) continue to proliferate throughout industry and institutional buildings, as well as many diverse applications such as pumps, factory automation, and process equipment, the problem of Harmonic Distortion increases directly with the number of VFD’s being used. While there are many ways to deal with harmonic distortion, there is often one… Read more »
The widespread adoption of variable frequency drive technology is allowing electricity to be utilized more efficiently throughout most of the world. Following right behind the adoption of drives is the establishment of harmonic distortion limits. This can cause confusion and may instill needless fear in people involved in the decision to apply variable frequency drives…. Read more »
When Silicon Controlled Rectifiers (SCR’s) are used in electrical controls, we frequently experience line voltage distortion in the form of “notches” in the waveform. The types of equipment that frequently utilize SCR control schemes and thus experience notching include DC motor speed controls and induction heating equipment.
Karl M. Hink, Executive Vice President – Motor protection filters are proven economical devices to improve inverter-fed motor reliability, increase motor life, and solve long lead over voltage problems. This paper demonstrates the benefits and applications of a number of different types of motor protection filters, including sine wave and single element low-pass filters. Output… Read more »
The evolution of power semiconductors has been so dramatic that today an insulated gate bi-polar transistor (IGBT) can be turned on in just 0. I micro-second. This results in the voltage rising from zero to peak in only one-tenth of a microsecond. Unfortunately, there are many motors in existence that do not have sufficient insulation… Read more »
Reactors have been used for many years to solve problems in variable speed drive installations. About ten years ago the use of line reactors started to become more common as they helped to solve typical problems on the input (line side) of variable frequency drives (VFD) and SCR controllers. They often have been used as… Read more »
Three phase line reactors offer an economical solution to a variety of application problems in variable-speed drive installations. Reactors solve problems on either the input or the output of the drive if the reactor is compensated to handle the effects of harmonics.