A-B Power Flex 400 Radio Noise

[a farm well pump 0]

Ok, My father, not being tech savy, has asked for a little help from me and I'm stumped. He owns a farm in Southern Utah (the desert). On the farm is a well pump to provide water from the aquifer below. We've recently installed two pivots and a variable drive motor to regulate the water pressure. As I understand it the AB power flex 400 regulates the motor on the pump by adjusting the Hertz (?) to slow down or speed up the motor to keep the water at a set pressure depending on the amount of needed water. The pivots use GPSs to track where they are but the signals are being blocked from large amounts of radio noise from the AB AC Drive Power Flex 400. Additionally there must be some noise going up the powerline because the radio in your car goes to fuzz if the Power flex is on. If you are within a quarter mile of the powerline the radio can't pick up a signal. This radio "jamming" occurs as far as 1.5 miles from the pump. Our worry is getting shut down by the power company from the noise problem affecting the lines. The variable pump system cost $12000 and they really don't want to drop much more into the system or they will just return it. Does anyone have any thoughts as to what exactly this problem is and/or how to fix it???? Thanks for any help with this. - Jason

[kpizzolatto 0]

Something is definitely wrong; you should not be seeing this much interference. Have you installed just a PowerFlex 400, or do you have appropriate enclosure, grounding/bonding, and line filters? Have you called your distributor? Even if you don't have a tech support contract, for 12000, somebody should at least talk to you. I just got a PF4 in for a well pump in my house; here's what the AB folks told me before I spent the money. Here's the typical stuff they warn you about: Install in bonded shielded box Lower your chop frequency Watch out for reflected waves--cable length is an issue, though the manual says not at 230V. Filter the incoming power appropriately. Filter the power to the pump if reqired for reflected wave protection. Use a VFD rated motor & cables. Here's some links to AB manuals that may help you: PowerFlex 400 Manuals Some particular ones you might find useful: PowerFlex 400 Input RFI Filters PowerFlex 400 Adjustable Frequency AC Drive Quick Start Adjustable Frequency AC Drive for Fan & Pump Applications User Manual Here's some general references about EMC Earthing, Bonding and EMC System Design for Control of Electrical Noise Good luck, and please followup when you find a solution.

[OkiePC 14]

The cause of this noise is the carrier frequency used by the drive to simulate a sinusoidal current at a varying motor frequency. The carrier frequency can be anywhere from 1khz to 16khz. It is often referred to as the PWM (pulse width modulation) frequency. There is a parameter (or several) in the drive that can be changed to switch the carrier frequency. Most of the time, people leave that parameter at the default setting. About the only time people mess with different settings is when they run into a noise problem like yours. Changing this setting will cost you nothing, but can have an effect on the rating of the drive. Reducing the carrier frequency can often result in more audible noise in the motor, but should not adversely affect its performance at the RPM ranges the pump is operating at. Increasing the carrier frequency can cause the drive to need to be derated, since its IGBTs will be switching faster, there will be more energy losses in the form of heat in the drive. I would enlist the help of a local expert first, and try reducing the carrier frequency. If it doesn't help, you can always put it back. The next step would be to install a line reactor, RFI filter, or isolation transformer between the power line and the drive. I should probably stop there since I have never used the 400. I don't know the voltage or HP rating you're dealing with etc. Here's a link to the user manual: http://literature.ro...um001_-en-p.pdf EDIT: Fixed wrong link. The PF400 carrier frequency defaults to 4kHz, and can be changed using parameter A168. See also A169. Edited 24 Aug 2010 by OkiePC

[kaiser_will 65]

How far is the motor drive from the motor (line length)? If it is terribly long, the drive may be creating standing waves on the drive output/motor leads. If the line length is short, the drive is creating RF waves on the main incoming power line. Yes, the power company will eventually have a problem with this. How many HP is the pump motor? What line voltage is the drive fed from? Did you have a building permit when the work was performed? Having the inspector come back and verify the workmanship might uncover the root cause. In the early VFD days, manufacturers often required isolation transformers on the drive output legs (motor leads) to keep this RF noise generation from propagating back into the main power feeder lines. As VFD IGBT (transistor) switch technology has improved, many applications do not require this additional hardware cost. Additionally in the early VFD days, manufacturers often required line reactors on the main power leads into VFDs to isolate drive operation from changes in the upstream power grid. Likewise, improvements in drive design have lead to many applications not requiring this additional hardware cost. You should be able to create an Allen-Bradley tech support account to get some service on this issue. If you run into an issue there, find out who your local A-B distributor is and get them involved. Most likely they have a drives support engineer, or know of a local A-B factory drives engineer you can consult with. These are all FREE ideas. Absolutely get the integrator involved, as they provided a solution that has created a problem. If they want to press you for payment upfront, follow the other methods of support first. Before embarking on adding a line reactor or isolation transformer, take a long look at your grounding. The motor ground, VFD ground, panel ground, main feeder ground should all be bonded properly. Can you get your hands on a power analyzer (AKA a Draenitz)? Talk to your local A-B distributor to see if someone can come out and slap a power analyzer on your power. There could be an issue going on with the power/grounding to the drive, that causes the drive to produce the RF noise, that may be out of your hands. Such as a weak leg, poor utility pole ground bond, or too much load for the step-down utility feeder transformer. Keep in mind your integrator will most likely want to pursue extra funding to resolve. Hold them to task to get the facts on the current situation before considering adding cost to resolve an issue that may be of their creation.

[a farm well pump 0]

Thanks for the leads! I'm nearly clueless in this field and will study up the course of actions that you all have suggested. I welcome more comments as I look into these current suggestions.

[a farm well pump 0]

Thanks to everyone for the help on this. I was pretty clueless. The final result is that the noise that was being sent up the power lines was eradicated by correcting/re-enforcing the ground. The ground that had been installed by the technician was, well, sub-optimal. We tapped a direct ground and this fixed the problem. There is now no noise going back up the power lines so we don't have to worry about the power company and/or the few neighbors getting upset at us when their FM/AM radios don't work. However, this didn't fix the noise that is conflicting with the GPS on the pivot. The GPS does work, but is intermittent and with some tweaks works most of the time. It seems that the best corrective action is to install a filter (at 800 bucks...). Since the pump is shutdown for the winter we plan on addressing this problem next Spring. Thank you again for your quick responses and the much needed direction. - Jason

[a farm well pump 0]

This was good advise and fixed the problem, Thank you!