VFD reliability?

[eagle lake sugar]

I added quite a few taps and mainline this year and am finding that I'm now slightly under-pumped. I'm considering buying a 60 to 75 cfm pump and some of the ones I'm looking at require a VFD. I'm of the mindset that simpler is better, and wonder about the reliability of adding another item into the mix. Have you folks that use VFD's had any problems or issues I should be concerned with? Thanks, Steve

[brookledge]

I have a 5hp nash liquid ring that is running on a vsb drive. I have a transducer to control the speed. It is set at 27" max rpm is 1800 and uses about 30 amps on the 220 line. Low rpm limit is set at 1135 rpm. (Have to keep enough water flow to keep liquid ring). At 1135 it draws 15 amps. The phase inverter converts to 3 phase.
One of the best features is you can detect leaks just by listening or looking at the rpm. I can go to the releaser and close off one line at a time to determine which line has the leak.
anyways it normally runs around 1200 to1300 rpm so it uses a lot less electricity with the vsd and im very happy with mine
keith

[BAP]

VFD are quite reliable. They have been used on Dairy farms for close to 20 years with good luck. We had one on our milking vacuum pump that had been going for 15+ years running about 16 hrs day/ 365 days a year without any problems. They react very quickly to vacuum needs and save a lot of electricity.

[BreezyHill]

20 years ago we looked into installing VFDs in our feed mill. We were recommended to not use them at that time was we are located on the end of the grid line. Our voltage level is often lower than it should be. This is not conducive to long life of VFDs at the time. You will need to check your voltage level and be sure that it is within the necessary range of feed for the VFD.

After that we installed power generaotros for our mill and found motors and lights last much longer. I have used one with good results for a short time on a molasses pump. But we changed the system and needed a larger pump and the VFD was sized to small

IMO VFDs are very good and I would strongly urge you to do your homework on voltage, housing the unit and enclosures, and find a unit that will work for you. Your choice in pumps is crutial to recover the maximum savings a VFD can provide since as Keith said he has to set a minimum rpm on his pump. On a rotary vane style I have seen rpms as low as 400 maintain vacuum on a 16 cow milking system. This is a pump that was earlier running at 1800 rpm. The farmer has insulated the room because in the winter the room would freeze while in the past a 24" fan would circulate air in the winter to cool the room and pump.

I plan to add a vfd in the future to my vacuum system when we are finished getting the entire farm back into production.

Ben

[GeneralStark]

VFDs are extremely reliable, as long as they are programmed correctly and as said above, as long as they have clean power. That said I just had one on my vacuum pump fail last week. Fortunately the vendor replaced it for free as it was clear there was a defect with the drive. They had a new one to me within 24 hours and within 15 minutes of installing it was running again.

They have so many advantages IMO such as motor protection, minimizing electrical consumption, speed control, etc. etc, that the risk of failure is well worth it.

[eagle lake sugar]

Thanks for the responses. It sounds like it's probably the way to go.