How Often do VSD's Save Money

All CE-marked VSDs are suitable for installation without additional harmonic filters.

One good way of saving money is installing VSDs on motors where there is a Peak Demand Tariff. Shaving off those starting current charges makes a good deal of economic sense.

http://cr4.globalspec.com/blogentry/17398/Significant-Energy-Savings-via-VSDs

Probably many, many more like this.

Super answer..can I use it please?

To add a little something, having used VSD/VFD's for many years on ESP's in the oil industry there added factor is the ramp up facility of the VFD which almost eliminates the shock load starting on bearings, couplings, shafts and twisting of the whole downhole completion.

The ramp up time does increase the run lift of ESP's and the cable a there is little or no inrush current.

Yes, ramp up (and down) are added benefits of using VFDs, they are also however available with soft starters in many cases so that alone is not enough of a reason to spend the extra money (although in small motor applications, VFDs are now at par with SS cost).

You also alluded to another benefit, starting current reduction. There are applications where the demands on the power system are so great that the only way to accelerate a motor is with a VFD, because it can provide 100% torque throughout the acceleration cycle without exceeding motor FLC.

And yes, you may use that statement on energy savings.

If you are installing VSD's to save money, they must operate at 40-70% of their rated RPM. If you do not want to add filtering, you can not have any electronic equipment installed in the building housing said drives. I was able to get a $60,000.00 grant from NYSERDA for my company in doing such. If I would have had to add filtering, that would have cost the company $20,000.00 to do so. So we live on and the company collected a check for $60,000.00 I no longer work for them. I have moved on to a better more relaxed atmosphere where I am more than welcome to participate and rewarded for my efforts of saving the company $$$

"..If you do not want to add filtering, you can not have any electronic equipment installed in the building housing said drives.." Why? What size motors are you driving? How old are the drives?

I've found all industrial equipment I use is insensitive to the small amount of electrical noise produced by VSD's.

All new 20HP motors, 80 of them = 80 drives. NYSERDA requirements indictive of 3% harmonic filtering. drives built in 2% harmonic filtering. No other electronic equipment = no needd to provide additional filtering. = %60,000.00 US check to the company. = I moved to a more worh while company that appreciates this incentive.

"..If you do not want to add filtering, you can not have any electronic equipment installed in the building housing said drives.

Could you please elaborate on this. I have not had a problem within the last 8-10 years or so with harmonics caused by a VFD. If there are particular cases where it is a problem I would like to be aware of it.

Thanks, Dave

Hi Dave, This was specified by the inspector from NYSERDA who was to approve the grant for the $60,000.00 Check. We argued about the Line Reactors and the 2% impedance vs the 3% they require. Due to he fact at that time there was no electronic equipment in either of the 2 buildings he accepted the standard 2% impedance and approved us for the check. I have not had issues with drives since 2002 with the improvements in design. And they get better every year.

Thank you for the clarification.

My experience is with batch pumping (sewage lift stations). A pump will use a lot more energy in the initial few seconds of starting than it will for the next minute or so of running at speed. I heard a statistic something along the lines of "reduce the pump speed by 10% and you will save 40% energy". Sorry, don't have a reference for that at the moment, will try to find it.

In addition to a fixed speed reduction, there are other ways to use VSDs to save energy costs. Take a station which has been sized for peak flow. During off-peak flow, the pumps are over-sized for the inflow, so they will slam on, run flat out for 30 seconds then stop. Each time they start, the inrush currents and energy required to start physically moving the liquids in the pipes will be very significant relative to the energy used for the rest of the pump cycle.

Now, what if we were to run the pump at half speed? (Start it at 100% for 5 seconds to flush the pipes and run the mix/flush valves, then return to a calculated speed). You will get much longer pump run times, so less energy-consuming starts. Include an algorithm that will increase the speed of the VSD proportional to the level in the well and the number of pumps running (http://www.multitrode.com/pump-station-manager/vfd.html), and you have a system that matches the inflow, to only use as much energy as it needs.

Longer, slower run-times are not only more energy-efficient (Energy = Money, so hence they are also cost-saving), they are better for the pumps, and steady inflow is much preferred by the treatment works in terms of system stability, instead of pulsed inflow that a normal headworks lift station would provide.

Contrary to popular belief, "inrush current" (really Starting current, inrush is something different) does NOT represent additional energy use. No matter what you use, the amount of ENERGY it requires to accelerate a load is a physics constant; nothing you do (within the laws of physics that so far govern our existence), will alter that amount of ENERGY. All a VFD does is lower the beak and lengthen the time. But if you plot it on a curve, the area of the curve is constant.

Note that I use the term energy. Current is not energy, it is a component of power (or watts). Watts are not energy either, energy in electrical terms is watts and time together.

http://cr4.globalspec.com/thread/55271