How to wire VFD for self serve

[softsuds]

Just experimenting around with a VFD drive on a spare pump/ motor. Thinking about building my own pump stand using them. My question is how do you wire the control wires to get different speeds ?
I assume you need a "3-stack" switch.
One stack to select what option, One to start the motor forward, but how do I get the different speeds ? Most VFD drives need a combination of two wires to select different speeds (three) ?
Any help would be appreciated.

 

[MEP001]

I'm not real familiar with VFDs, but I don't think you would just wire it to a switch for different speeds. The systems I've seen use them run a pressure transducer to control the motor speed so the VFD itself controls the pressure instead of a regulator, then when you have a "pressure boost" button the pump is just run faster.

 

[tbarnard]

Depending on what you have for a drive, there should be digital inputs that you can program for different speeds. For instance, Digital input 1 (DI-1) would be start forward, DI-2, would be programmed for 60 hz (full speed), DI-2 programmed for 45 hz (75%). Make input common to DI-1 to enable drive and input common to DI-2 at the same time to command to full speed. Check the owners manual for the drive for specifics on wiring and programming. MEP it right, the best way and most common way is to use a pressure transducer watch pressure and ramp the drive to reach a pressure set point. If you have a full-featured drive, you may be able to wire a pressure transducer to an analog input on the drive, set up a PID loop in the drive, and use the digital inputs for different pressure set points. I work with drives almost every day and am factory certified to do startups for 3 brands, that being said, my lower pressure functions at my wash are done with a high pressure solenoid feeding a second lower set pressure relief on my pump. Drives are nice but another mechanical/electrical component to fail... And and expensive repair if they do fail.

 

[lilb93]

I am also thinking about playing with VFD'S. There used on our Haas CNC Lathe and CNC router and CNC mill. The newer oner will run 3 phase motors with no three phase power in the building. Some are program simple and some are a nightmare to program with over 300 programs to get right. The simple ones you would program your pump to run , lets say at 900 RPM. You would put a SUPER Button on your coin box when depressed it would contract a relay which would have 24V running from the coin box to the relay giving the VFD 120V to the Program wires telling it to run at 1250 Rpm. Would have to check the program to go back to 900 RPM. Probably switch off of high pressure to a low pressure switch.

 

[mjwalsh]

I am also thinking about playing with VFD'S. There used on our Haas CNC Lathe and CNC router and CNC mill. The newer oner will run 3 phase motors with no three phase power in the building. Some are program simple and some are a nightmare to program with over 300 programs to get right. The simple ones you would program your pump to run , lets say at 900 RPM. You would put a SUPER Button on your coin box when depressed it would contract a relay which would have 24V running from the coin box to the relay giving the VFD 120V to the Program wires telling it to run at 1250 Rpm. Would have to check the program to go back to 900 RPM. Probably switch off of high pressure to a low pressure switch.

If you search some of Tom Hoffman's posts ... it should come up describing something similar that he did. Based on my admittedly limited VFD - PLC - PID experience ... I would say a capable enough PLC could be helpful ... especially if you set up a PID loop like TBernard made reference to.

 

[wash4me]

A pid loop feature is what you want so it will automatically sense pressure and adjust rpm accordingly. A 4-20 ma or 0-10 volt transducer plumbed in and an hour on the phone with tech support should do it. On your rotary dial you will need an extra spot or just install a button to boost the pressure as someone noted above. All that being said you could do the same thing with 2 regulators and a solenoid valve that just shuts off the lower pressure one on "boost". A Vfd is overrated for this application.