VFD Installation

[A/A Fuel GTX]

I've got a customer wanting to use VFD's to control 3 phase exhaust fans in his shop. I've never installed VFD's before and I'm wondering if there is anything special about these or are they simply speed controls with wiring similar to mag starters with L 1,2,3 on top and T 1,2,3 on the bottom of the controller?

 

[sgunsel]

That's about all you need to install, but all connections typically are on the bottom. VFD's replace the start and overload relays and can be easily programmed for soft starts. They are easy to install and set up. Once you install one, you will like it. So will the customer. Don't forget to program a reasonable max speed or the fan could come apart!

 

[magoo66]

L1,L2 and L3 on the top, T1,T2 and T3 on the bottom, you can change rotation by programming so no need to swap phases. All of the ones that I have hooked up specify that the load side conductors must be shielded with metallic conduit. I think this is to reduce induced voltages. Also, the early ones were notorious for producing harmonics. Hope this helps!

 

[wirenut601]

vfd

vfd

pretty much, line 1 2 3 and load side 1 2 3 but you should also be able to put in a control circut and use a thermostat or timer depending on what the fan is for. just to get air exhausted or is there an air intake on another wall and and this is to regulate tempature.

 

[wirenut601]

vfd

vfd

magoo is correct line and load wires should be separate in their own metal conduits.

 

[A/A Fuel GTX]

just to get air exhausted or is there an air intake on another wall and and this is to regulate tempature.

This is just to exhaust air in the shop. Thanks for the responses.

 

[sameguy]

Forum: Power Quality & Surge Protection
Look there, then read the instructions for the drive.
3 pipes, line, load, control

 

[weressl]

I've got a customer wanting to use VFD's to control 3 phase exhaust fans in his shop. I've never installed VFD's before and I'm wondering if there is anything special about these or are they simply speed controls with wiring similar to mag starters with L 1,2,3 on top and T 1,2,3 on the bottom of the controller?

Any idea how and what is going to control the speed?

 

[Cow]

Any idea how and what is going to control the speed?

Or how the drive will get it's start/stop commands?

Most of the time we use 2 wire start if they don't want to use the drives keypad. Could be as simple as running a 2 wire LV cable over to a switchbox if that's what you're looking for...?

 

[ptonsparky]

Don't forget that unless you have another source of cooling for the motor, you may want to limit the low speed. Otherwise I agree with cow. Fun.

 

[A/A Fuel GTX]

Any idea how and what is going to control the speed?

I assumed the VFD was the speed control and the start/stop commands were initiated at the VFD itself not unlike a motor control with start/stop buttons. Remote switching could be an option but not a necessity here. Please steer me in the right direction if I'm going astray.

 

[weressl]

Don't forget that unless you have another source of cooling for the motor, you may want to limit the low speed. Otherwise I agree with cow. Fun.

In the case of centrifugal fans there is no usable flow below ~30% of the full scale speed and heat becomes the problem with centrifugal loads only at the very low ~2-5% end, but with some motors, not even there. So limiting fans, agitators and pumps at 30% speed is quite common.

 

[weressl]

I assumed the VFD was the speed control and the start/stop commands were initiated at the VFD itself not unlike a motor control with start/stop buttons. Remote switching could be an option but not a necessity here. Please steer me in the right direction if I'm going astray.

Both assumptions CAN be correct, but you have to ask your Customer; what is he trying to accomplish and how?

Give you an example. In chemical plants control rooms are often pressurized to keep the flammable chemicals out and allow the room to be non-classiified. There are various openings and doors that are constantly changing the 'leakeage' volume out of the room.

The objective is to maintain a constant pressure difference between the outside and inside, so the ASD controls the volume of air pumped into the room by a pressure differential transmitters 4-20mA signal. Since the drive is in an MCC, remote from the control room a manual start/stop station may be located in the control room and wired to the ASD(Adjustable Speed Drive) itself. There may also be a fire alarm system shutdown wired into it and and alarm signal wired out of it to let people know if there is a problem with the drive.

The ASD's are quite flexible to allow for these various options to be wired in and most of them have integral power supply to power these contacts, although not all and require shielded and twisted pair wires even for the discrete(on/off) signals.

Most manuals are quite good to describe the installation and programming requirements and the factories are helpful. (Early manuals of Japanese drives used to be hilarious with their Jinglish translations.) I am also sure that many folks on this thread would be willing to spend some time on the phone with you if you contact them via a private message, myself included.

 

[A/A Fuel GTX]

Both assumptions CAN be correct, but you have to ask your Customer; what is he trying to accomplish and how?

I appreciate your willingness to coach me here. In this situation, all my customer wants to do is remove fumes from inside his shop and send them outside. There will be times when maximum air movement is desired as well as times when it would be nice to be able to tone down the the CFM's. Would the VFD have the ability to do that as a stand alone device or do I need to read more into this? The VFD will be controlling 2 exhaust fans, 3 phase, 480V at about 2A FLC per fan.

 

[ptonsparky]

Automatic control via 4-20ma/0-10v is a bit more complicated but simple high/low switch will work or just the control on the VFD if manual control is OK. Go online and download a manual. Automation Direct has them readily available. You do not need a high end drive for this application.

If I can figure it out, dang near anyone can.

 

[sgunsel]

Start, stop, and speed adjustments can be done with the VFD alone, assuming it is accessible. You can program in min and max speeds as well as lockout reverse to help make sure nobody accidentally screws up. Remote control is pretty simple as they typically operate at low voltage DC (provided by the VFD).

 

[Open Neutral]

The VFD will be controlling 2 exhaust fans, 3 phase, 480V at about 2A FLC per fan.

Most FVD's are designed to run one motor. RTFM carefully if you need multiple loads.

The average VFD has 3-4 ways to control the speed. One might be a pot. You could use two fixed resistors in series, with a toggle switch shorting out one as needed.

Also, unless the fans are rated "inverter duty" you may want a load reactor. The FVD creates faux sine waves full of sharp transitions; the reactor helps reduce those.

 

[zbang]

You might want to download the manual for the drive you're thinking about using and give it a read.

 

[ptonsparky]

You will need individual overload protection for each fan and they must be suitable for use on the load side of the vfd. We have worked on a system that had individual manual motor starters with the overload contacts in series to shut the drive down entirely in case of a problem. A simple matter then to determine which motor was causing grief, bypass it, and continue with other(s) until a repair is made. In our case the drive would increase the speeds of the other fans to make up for the loss of one.

Seemed to work well.

 

[tom baker]

One caution is some motors are not compatible with VFDs. The high voltage wave it creates can damage motor windings, so we typically see inverter duty spike resistant windings.
And as mentioned, fan motors depend on air flow to cool the motor. Motors have a turndown ratio, IE range of low to high speed. You may not be able to go below 30 hz with out overheating the motor. There are motors designed for low speeds

Determine how the speed will be set? Keypad or? Automatic based on air temp?

The biggest advantage of VFDs is the energy savings. Running at 50% speed is 1/8 of the power as 100%, due to the affinity laws