# Altivar 61



## raker.robert (Jun 25, 2010)

There is a 1000' well with a 3 phase 7 hp pump puming into a 40,000 gallon holding tank. He installed an Altivar 61 for the frequncy drive to get his 3 phases and for the other benifits that come with VFDs. There is a preasure transducer next to the VFD that is reading the dynamic preasure of the system and that is sending the signal to the PID parameter in the VFD. One issue is that there is not a pipe taking the inlet water to the top of the 40,000 gallon holding tank. So both the intake and outtake come from the bottom. This causes issues with chlorine(spellling) and also the reading on the preasure transducer. This also causes the sediment in the bottom of the tank to stir up. Our old pump put in roughly 12 gallons a minute and this pumps is putting in 45. It ramps upto 45 gpm. It is causing everyones water to be poor. I know we need to get the inlet pipe to the top and that will fix it but we dont have the funds. That made me decide to download the manual and teach myself. I have delt with them in Tech School 8 years back but now my expertise is in smart grid and demand response. Now that you konw the story let me aks the question. 

Can I use the PID parameter in the VFD to ramp up the gpm as needed rather than ramping it up to 45 gpm. If so how do I take into consideration the preasure that is built up from the pump putting water into the bottom of the 40,000 gallon holding tank if possible?


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## MDShunk (Jan 7, 2007)

I see a few options:

fix the inlet to the top of the tank
installal a flowmeter on the existing inlet and use that for the drive feedback instead of the pressure transducer.
Change the max Hz parameter to approximate the Hz value that equates to 12gpm.


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## Forsythe (Feb 6, 2012)

The great thing about a Schneider drive is that you can call from the drive, anytime of day/night and someone can assist you with programming over the phone. You don't even have to be an Electrician. 

888-778-2733, option 1, option 4

I kinda know those guys :thumbup:


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## JRaef (Mar 23, 2009)

raker.robert said:


> ...There is a preasure transducer next to the VFD that is reading the dynamic preasure of the system and that is sending the signal to the PID parameter in the VFD. ... He keeps telling me that is "ramps up nice and slow" but my point is that is nice and all but quit making it ramp upto 45 gpm.


The PID function is not just about ramping, in fact ramping is actually a separate issue. The PID function is about MAINTAINING something. If you have a pressure transducer, then it is supposed to be maintaining pressure. If it is ramping all the way to the top speed every time, that means one of two possible issues:
1) The pressure is so low to start with you need the entire output capability of that pump to get there in the first place. If you had been using a 12GPM pump and it was working, now you have a 45GPM pump and it is not, something is wrong.
2) The PID control function is not turned on or is not set up correctly. I'd bet a paycheck on this being the case.



> ... I dont feel that this guy he has hired knows what he is doing. I have met him at the site to ask questions and I seemed to know more about the VFD than he did.


Hence my willingness to bet a paycheck. Had he really known what he was doing, he would have explained this to you. Commenting that "It ramps up nice and slow" sounds like all he did was program the ramp time.



> That made me decide to download the manual and teach myself. When I talk with the guy that put it in he get ofensive because he hired an incompitant electrician to program this.


Good for you. 



> Can I use the PID parameter in the VFD to ramp up the gpm as needed rather than ramping it up to 45 gpm. If so how do I take into consideration the preasure that is built up from the pump putting water into the bottom of the 40,000 gallon holding tank if possible?


As I said, the PID loop is for maintaining a setpoint and must be related to the "process variable", the input data input, which in this case is pressure. So you will not be able to use it to control flow unless you change to having a flow transducer as the process variable. If you do that, then you will lose the ability to maintain a system pressure. 

A classic and simple example of a PID control loop is your Cruise Control on your car. You set the speed you want, that is your "Setpoint", related to system pressure in your application. Engine HP is the "Output" that is necessary to maintin speed, in your case the pump output (it's a little more complex because of head and flow). The throttle is the "Output Control Element", in your case the VFD . The speedometer is the "Process Variable" input, in your case the Pressure Transducer. If you set the Cruise control for 60MPH on flat ground, the controller holds the throttle steady to maintain speed. But as you go up a hill, the controller opens the throttle to increase the engine HP in order to maintain that speed. If you rest your foot on the gas pedal, you feel that happen. 

In your case, if someone takes a shower, the demand increases and the pressure drops, so the controller slowly speeds up the drive to maintain that pressure by increasing flow. If 150 people flush their toilets over a 5 minute period at half time of the Superbowl, there is an increase in demand but the rate of change is not fast, so the controller responds by increasing output speed to make up for it, a "Proportional" response to the change in the process variable. If a fire pump goes on however, a slow increase is not going to be good, but the rapid drop in pressure is seen by the PID control loop and causes it to respond by changing the RATE of increase of the output, so the response is "Integral" to the rate of change. If there are a large number of people staggerring their sprinkler systems on and off over the course of 6 hours in the morning, the controller anticipates the number of changes and slows down the decel process, knowing that it's likely to have to ramp up again sono. So that response is "Derivative" of the number of changes over time. Proportional, Integral, Derivative is what PID stands for.

So how does that relate? Go back to issue 1. If there is *zero* pressure when you turn it on, the PID response may indeed be to increase the VFD output speed to maximum in order to initially bring the system pressure up to the setpoint. But you have a tank and your outlet pipe is on the bottom of the tank. The only way there can be ZERO pressure on the transducer is if the tank is empty. So if you are pegging the speed, there is something seriousl;y amiss in the PID programming, if any.

So your "expert" is not. He is probably faking it, sounds like all he has done is program the ramp times, which does NOTHING for making the pump respond correctly to the process variable.

Separate issue, I have programmed more than 75% of the brands of VFD on the market, out of all of them, the only one I have never been able to get the PID loop to work correctly on was a Scneider ATV 71, which uses the same programming as the 61. I think it has the most difficult to use interface for programming a PID loop on the market. I once used up all 600 minutes of my cell phone time with their Tech Support, who had no idea what to do, none of them had ever done a PID loop. That was a few years ago now, but I can believe it may be that your "expert" may have tried and gave up.


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## raker.robert (Jun 25, 2010)

From your analogy of the cruise control it would be nice to set the PID using 60 mph as the "set point". Then with the programming set it so the "Output Control Element" VFD will turn the "Output" on when it drops to 50 mph. When the "output" comes on rather then push the throttle to the floor just accelerate slowly and never at any point pumping more than 12 gpm. There might be a point when the resevior just maintains rather than fills up but that is ok atleast it will not be pumping to the point of stirring up the sediment. We have 40,000 gallons of storage to manage. Given we dont have any major water leaks we should always be able to replenish it in the evening time/night time. I think that I have been able to make it run that way by lowering the max Hz parameter. It appears to be an industry standard to set the min Hz parameter to 20 Hz. This will allow the pump to always have enough power to pump enough water to keep it from heating up. Thanks for all the help, this forum is always a great place to learn.


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