Need help setting VFD speed in Hz.

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milemaker13

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To the point where I am trying to set this VFD to run in 2 speeds. I don't know where to begin! Well, what I mean is what Hz should I try to run at? I'm not sure if I should be using the full range (0-500 hz) or a smaller set?

Does anyone have a starting suggestion? I've tried 150 and 60 but the drive trips before the fan gets any speed.

5hp fan, 7.5 hp drive... Any help?:?
 
milemaker13 said:
To the point where I am trying to set this VFD to run in 2 speeds. I don't know where to begin! Well, what I mean is what Hz should I try to run at? I'm not sure if I should be using the full range (0-500 hz) or a smaller set?

Does anyone have a starting suggestion? I've tried 150 and 60 but the drive trips before the fan gets any speed.

5hp fan, 7.5 hp drive... Any help?:?
Click to expand...

Typically the engineer that designed the system will tell you what speeds to run it at. It is doubtful that they would ever exceed 75-90 Hz.

There are a bunch of reasons the drive might be tripping. A slower accel might help.

It is also possible that being a fan application that the fan is turning at the time the drive is turned on. This problem is solvable with what is often called a flying start function, or the use of a brake to keep the fan stationary when deenergized.
 
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You typically cannot run a fan (centrifugal) faster than the base speed it was designed for. In a centrifugal load, power varies by the cube of the flow change. So if your fan was designed for a 5HP motor and you try to run it at 150Hz, that is 250% speed (assuming 60Hz since you used HP instead of kW). So the fan will need 15.62 times (2.5 cubed) more power to run at that speed, or 78HP! Your motor nor your VFD can deliver that much power, so it trips on overload.

What the VFD is supposed to be used for is to LOWER your fan speed below what it is normally designed for. If someone sold it to you expecting it to run higher, then they did not know what they were talikng about.

What exactly are you attempting to do here?
 
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Driven Hard

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milemaker13 said:
To the point where I am trying to set this VFD to run in 2 speeds. I don't know where to begin! Well, what I mean is what Hz should I try to run at? I'm not sure if I should be using the full range (0-500 hz) or a smaller set?

Does anyone have a starting suggestion? I've tried 150 and 60 but the drive trips before the fan gets any speed.

5hp fan, 7.5 hp drive... Any help?:?
Click to expand...

Usually the drive will match the motor hp your Drive is a little larger but can still be used normally min speed is set to 0 max speed 60hertz BUT because your drive is larger dial it down a bit to 50 hertz make sure your ampacity ratings from the motor are set-up properly in the drive, also is the motor inverter duty some motors just dont work well with varrying its voltage and frequency. try at 50hertz take an amperage reading. work from there.
 
Its part of a heat extraction system. They made the deals upstairs, I was just told to make it all work;)

Basically, this is just a 2 speed wall fan.

I don't have much (any) exp with VFDs. So I was looking for some basic starting points. No help from installer.. probably better that way. I see now that 60 hz is my base speed, and I can go lower from there.
 
milemaker13 said:
Its part of a heat extraction system. They made the deals upstairs, I was just told to make it all work;)

Basically, this is just a 2 speed wall fan.

I don't have much (any) exp with VFDs. So I was looking for some basic starting points. No help from installer.. probably better that way. I see now that 60 hz is my base speed, and I can go lower from there.
Click to expand...

That seems reasonable.
 
Typically on a 2 speed motor for a fan, the low speed is 1/2 of the high speed. So 30Hz for the low speed, 60Hz for full speed.

With a VFD, you have a decision to make on how you are going to select the speed. Your choices are;
  1. Use the keypad on the VFD
  2. Use a Potentiometer (pot) on the VFD if there is one.
  3. Use an external pot wired to the analog input of the VFD.
  4. Use another external analog signal from a higher level control system.
  5. Use digital inputs in the VFD to select preset speeds that you program into the VFD.
For something this simple I would think #4 is out. #1 & #2 presume the VFD keypad is accessible and unless you have a fairly sophisticated enclosed version, it probably isn't. So most of the time in a situation like yours it will be #3 or #5. If all you want are two exact speeds, then #5 it is. You would set up the VFD to run at 60Hz unless the Digital Input that you select as "Low Speed" is closed, in which case it runs at 30Hz. Simple and straight forward. The alternative is to wire an external pot to the drive and tell it to follow the analog value of the pot input. The advantage to this is that the user can infinately adjust the speed to match conditions. The down side is that is sometimes too much decision making for some people. ;) :happyyes:

Side issue, you will also need something that tells the VFD to Start and Stop, and you need to decide if that is to be a 2 wire or 3 wire command. 2 wire means you just close a maintained switch, like your light switch, to one of the digital inputs and as long as that switch is closed, the VFD runs. If power fails, when it comes back on the VFD will immediately turn back on and run at whatever speed you had previously had it running. 3 wire control means you have a momentary Start push button and a momentary Stop push button. When you hit Start, the signal goes through a relay in the VFD that holds the command in until you hit the Stop button or the power fails. If the power does fail, the VFD will NOT come back on until someone tells it to by pushing the Start button again. This is a safety issue. Only you can decide which is best for your situation.
 
Jraef- I am using method #5, digital inputs. I have the 2 wire scheme for starting. Unexpected starting isn't a problem, and also this unit needs 2 seconds between power up and the run command, so I'm not sure it would re-start on its own anyway(which is also not a problem).

I am having a little trouble with the two speeds. I have been giving the run command, a low speed command, and a high speed command. From what you write, maybe I don't need two speed commands? Only Run and speed#2...
 
milemaker13 said:
Jraef- I am using method #5, digital inputs. I have the 2 wire scheme for starting. Unexpected starting isn't a problem, and also this unit needs 2 seconds between power up and the run command, so I'm not sure it would re-start on its own anyway(which is also not a problem).

I am having a little trouble with the two speeds. I have been giving the run command, a low speed command, and a high speed command. From what you write, maybe I don't need two speed commands? Only Run and speed#2...
Click to expand...

You should be able to do it either way, but if you say "Run - High" and have another signal that says "Low Speed", you have to have the Run-High signal closed to make it Run, then make sure the program recognizes that if you say Low Speed, it overrides the High speed command. Most VFDs will default to act this way, but without knowing what you have I can't say for sure. A separate Run command and separate High and Low speed commands is a bit cleaner sometimes, but consumes more inputs. That isn't likely an issue in your situation though.

Again without knowing your brand and it's peculiarities, its fairly common that somewhere in the programming, you have to tell the VFD WHERE the speed command is going to come from, i.e. digital inputs or analog input or keypad etc. If you didn't change that in your programming, it might be that the factory default is Keypad. Every brand has their own philosophy on default settings, you have to go through the appropriate programming steps to fully understand what you need to do.
 
The drive is a Lenze AC Tech SMVector freq inv model# ESV552. Says made in USA :thumbsup:

The digital inputs are pretty straight forward... but I'm stumped.

So I have term#4 as my digital referance/common. My book says to wire this thru my start switch back to term#1 for start/stop control. It also says to wire #4 thru another switch back to term#13a,b,c or d. These are the digital inputs, which are configurable in the parameters.

I have adjusted p100(start source)to read off the term strip vs. the keypad.
p101(std ref source) to preset speed#1 vs keypad.
p131(preset #1) & p132(preset #2) adjusted for 30hz and 60 hz.

So an input to term 13a should start the low speed 30hz, and 13b should start high speed 60hz.

But it won't change speed. I had all 3 inputs at first (run+low, or run+high), then I tried only 2 inputs (run, or run+high). Doesn't want to change speed for me.

Got anymore of the good stuff for me?
 
SUCCESS!!:D Seems I had my speeds set, but didn't have the drive set to look at them. P121 & 122 set the referance to the preset speeds.


I want to thank everyone that chimed in to help me. This was my first VFD install and I couldn't have done it without everyones help.

Thank you.
 
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