Regenerative power drives and harmonics: they sound complicated, but it’s easy to see why they’re an electro-mechanical wonder in our every-day lives. For example a smooth ride on an elevator or escalator means the motor behind the scenes was re-generating its own power. How? When moving us up, the motor loads with energy, and when braking (slowing), the negative torque returns kinetic energy fed to the motor. All the while voltage and current are kept in “harmony” by a Variable Frequency Drive (VFD) to mitigate harmonic distortion when voltage and current fluctuate. In this post we’ll demystify traditional VFDs, harmonics and regenerative Drive technology. Next, we’ll review the Yaskawa Matrix U1000 Drive, a compact VFD product using this technology to literally consolidate your power investment and convert your money into mechanical power.
Harmonic Control in Electrical Power Systems
In industrial applications, you’ll find variable frequency drives wherever mechanical systems like motors and pumps are used. VFD’s convert electrical energy to mechanical energy. They make motors more efficient by matching frequency and voltage applied to an AC motor as motor speeds and motor loads vary. The drive matches these variables for motor applications by converting the input AC voltage to DC voltage and then back to AC. A critical performance requirement in VFD’s is that they mitigate electrical disturbance typically experienced as harmonics. Though not unique to variable frequency drives, harmonics impact photocopiers, personal computers, laser printers and other every-day equipment where electrical disturbance is present.
To normalize this electrical power phenomenon, the IEEE 519 Standard sets limits (<5% current distortion) on harmonic distortion to establish Harmonic Control in Electrical Power Systems. This includes utilities where harmonic distortion occurs naturally within the power system or is created on demand by end-user customers.Regenerative Power in Variable Frequency Drives. When a load pulls a motor faster than its designed RPM speed, as in the case of a descending conveyor, the excess kinetic energy is stored and re-used in the power grid – any source of power – which feeds motors. Regenerative energy occurs in manufacturing when any kind of inertia and tension is placed on machinery. Examples of this regenerative braking include large blowers, machine tools and heavy equipment when slowing down (i.e., braking). The job of a VFD is to synchronize motor operating speed with the correct voltage and current during acceleration and deceleration.
Yaskawa U1000 Matrix VFD (5 HP – 350 HP) Stands-Alone
Let’s apply harmonics and regeneration into a recent VFD innovation. Harmonic performance and regenerative energy is where the Yaskawa Matrix U1000 Drive shines. Traditional variable frequency drives require additional components in what’s called a DC Bus that includes contactors, fuses and rectifiers to control current. In this Common DC Bus configuration, the DC Bus is separate from the drive. The components work overtime trying to keep fluctuating, one-direction (unidirectional) voltage and current in harmony. Yaskawa’s Matrix Drive is an all-in-one drive solution to the challenges discussed above. Built in technology creates a variable output by switching directly from the input power, eliminating the need for a DC Bus. This allows for bi-directional current and voltage flowing directly to the motor which improves harmonics and efficient regenerated energy. Plus, elimination of the DC Bus gives the Yaskawa Matrix drive technology a smaller footprint, faster setup and reduced maintenance.
Pairing Drives with Motors
for Efficient Power Regeneration
Selecting regenerative VFDs and reducing harmonics requires careful evaluation of how they will interact with other motor system products such as drive isolation transformers and line reactors. They must be paired correctly with electrical motor selection. You can simplify the equation with Yaskawa’s Industrial U1000 Matrix Drive. (U1000), a compact VFD that addresses many concerns in this regard.
Looking for a VFD solution? Before making a choice, do a careful and complete analysis of your application. Consult with a local electrical contractor who has done this type work. Download EECO’s “ Dedicated to Drives” brochure and call for assistance when selecting and servicing variable frequency drives and components. Contact us at: AskEECO@eeco-net.com or call 800.993.3326 to speak with an EECO motor specialist.