Help on this oddball

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Dennis Alwon

Dennis Alwon

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I have never run into this before, in fact, I have never wired a VFD that I can remember. This unit is supposed to be a VFD and a single to 3 phase converter. I don't understand the 0-590 hz

Any experience with this. Not sure why they need it for a well pump----3 phase 5 hp

1661959737164.png
 
I have limited VFD experience, but it looks like it takes in Single Phase Voltage X and produces Three Voltage 0-X at any Frequency between 0 and 590 Hz. The variable frequency would be the "variable speed" part of the motor and the voltage would be reduced to keep constant current as the Impedance of the Winding Inductance goes down with Frequency.

Mark
 
I guess I didn't think the frequency could be raised that high.

The other question is whether or not the 3 phase would be a delta (240 V) or a wye (208 V). I assume 240V 3 phase
 
I’m guessing they need it because the pump is 3 phase and they don’t have 3 phase available. Likely to be set to an output of motor nameplate voltage, 60 HZ, and left that way.
 
busman said:
I have limited VFD experience, but it looks like it takes in Single Phase Voltage X and produces Three Voltage 0-X at any Frequency between 0 and 590 Hz. The variable frequency would be the "variable speed" part of the motor and the voltage would be reduced to keep constant current as the Impedance of the Winding Inductance goes down with Frequency.

Mark
Click to expand...

The conventional way to describe it would be “constant V/HZ ratio.”

And it’s actually the opposite of your description - as the frequency goes up, so does the impedance, so the voltage increases accordingly. Maybe that’s what you’re saying?
 
We did a few that were 1300 Hz. They were designed for the aircraft manufacturing industry. They were mostly around 55 kW water cooled units.
 
retirede said:
The conventional way to describe it would be “constant V/HZ ratio.”

And it’s actually the opposite of your description - as the frequency goes up, so does the impedance, so the voltage increases accordingly. Maybe that’s what you’re saying?
Click to expand...
Yes, I said it badly. Z = L * f

Mark
 
I think the 590Hz capability would be targeted for high speed motors and 400Hz motors in general. 590Hz would be 47.5% higher than 400Hz.
They probably have a common design for the VFD that can handle a wide variety of applications.
 
Dennis Alwon said:
I guess I didn't think the frequency could be raised that high.

The other question is whether or not the 3 phase would be a delta (240 V) or a wye (208 V). I assume 240V 3 phase
Click to expand...
Dennis, I would assume where it says "OUT: 3X0-Vin..." means that whatever voltage goes in, you get 3 phases of that exact voltage out.
 
I install a lot of Grundfos submersible well pumps. However I haven't used the Grundfos VFD. I normally use either a Pentair intellidrive (made by Danfoss) or a Yaskawa. Up thru 2 hp we can use single phase in and single phase out drives. Over 2 hp we have to use a 3 phase motor. Typically we do not have 3 phase power available in domestic pump applications. I have installed as large as a 15 hp sub motor with a drive on single phase incoming power. Three phase power was not available.

Don't worry about the 590 hz capability. Normally we set max hz at 60, with a few exceptions. I'm am going on a service call tomorrow that the original installer has 3 20 hp Hitachi sub motors set at 67 hz.
 
The issue has been that the well guy has replaced 3 of those vfd units. The 5 hp 3 phase and pump is 500' in the ground and about 200' to the house. They ran #6 copper. The pump, I just learned is rated 208-240v so vd doesn't seem to be the issue.

I was trying to figure out why he was having a problem. I know the voltage at the house is 227v-- very similar to my home and they are just down the road a 1/2 mile or so
 
A single phase 230 volt motor with 700 ft of wire would need #3 wire to keep voltage drop within manufacturer specification. The 3 phase motor can use #6 wire.

Yes the grundfos motor is dual rated 208-240 volt. Most other brand sub motors are not.

The biggest reason for a VFD is to reduce pump cycling. A standard pump installation uses a pressure switch with a 20 psi differential between on and off. The pump runs at 100%. The excess flow of the pump over what is being used fills the pressure tank. An 88 gallon pressure tank actually stores a little over 20 gallons of water. Let's assume that this 5 hp pump set 500 ft deep pumps 20 gpm and your using 5 gpm. That means that when the pump turns on, 15 gallons per minute are filling the pressure tank. That means the pump will run for 80 seconds and shut off. Then water will flow out of the pressure tank at 5 gpm. This will take 4 minutes. Then the cycle will repeat over and over. With the vfd, the pump will run at what ever rpm it takes to maintain the 5 gpm flow at the predetermined pressure, say 50 psi. When demand is satisfied and the pump runs at minimum speed for a pretty amount of time, it goes to sleep. Then when pressure drops to the programmed differential pressure the pump starts back up again. I normally program a 15 psi differential and boost the pressure 5 psi before the pump goes to sleep.
 
This 3 phase 240 v motor runs at 12 amps and T 430.250 shows 15.2 amps

So if the motor draws 12 amps on 3 phase then what would the draw be on the feeder which is single phase. Is this what @Dzboyce is talking about. The feeder would be drawing 28 amps based on 5 hp single phase motor?????
 
Dzboyce said:
I install a lot of Grundfos submersible well pumps. However I haven't used the Grundfos VFD. I normally use either a Pentair intellidrive (made by Danfoss) or a Yaskawa. Up thru 2 hp we can use single phase in and single phase out drives. ...
Click to expand...

Would a pump motor driven with a single-phase VFD output have to be of a permanent split capacitor type?
 
It only goes up to 590 Hz because various governments banned VFDs that go over 600 Hertz because the Iranians were using them to run centrifuges. Now if you need a VFD that exceeds 600 Hertz like for a spindle, you have to get a special license from some government entity. Like the Iranians can make a nuclear weapon but can't make a VFD that exceeds 600 Hertz.
 
Any help on this question in post 15

This 3 phase 240 v motor runs at 12 amps and T 430.250 shows 15.2 amps

So if the motor draws 12 amps on 3 phase then what would the draw be on the feeder which is single phase. Is this what @Dzboyce is talking about. The feeder would be drawing 28 amps based on 5 hp single phase motor?????
Click to expand...
 
gadfly56 said:
Dennis, I would assume where it says "OUT: 3X0-Vin..." means that whatever voltage goes in, you get 3 phases of that exact voltage out.
Click to expand...

I read it as out 3 phase, 0 to Vin.

VFDs have to be able to change both voltage and frequency or the driven motor won't be happy.

Jon
 
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