Yet Another VFD Question...

[roger oldre]

It took me longer than 20 minutes to type that up lol. overclocking the VFD doesent increase HP as someone else has stated it increases the frequency of the cycle to run faster than the 60 hz synchronous motor was built to run just as decreasing the hz to less than 60 hz makes the motor run slower. there are constant output state drives that can maintain the torque at diferent speeds. I sincerly doubt that you let the smoke out of your VFD by trying to start your motor unloaded even though it is 5 hp and the VFD was rated for only 3. from the factory they are usualy set to ramp up to the requested speed. This type of start reduces the inrush current that can be as much as 3 times the running draw of a motor. Most VFD's today are self protecting against many mistakes. they simply fault, not fry. DD I can and do understand your fear and uncertainty relax a little. As I said I wasnt trying to be mean I am trying to understand some things as well.

You may feel that it is backtracking a bit but if you dont mind covering the bases I would be happy to work through your drive requirements with you.

What speed range are you shooting for?
what is you maximum diameter turning/ minimum?
Can you supply a picture of the drive as it is?
can you supply thye size for the maximum size pulley on the headstock?
what is the center distance available from spindle to the motor shaft?
I can crunch some numbers in a couple programs I have and let you know the results.
what type of belt do you want to run? V belt, cog/timing belt, poly V?
Roger

[Mike Cruz]

Let me rephrase. And I have to apologize for using "overclocking" incorrectly. I understand the hz adjustment, and that has to do with speed.

When you get the VFD, you have to input the amps of your motor. Even if you have a "2 hp" VFD and a 2 hp motor. Not all 2 hp motors pull the same amps. A 2 hp motor could pull 5.2 amps or 6.0 (maybe more?). So, if your motor pulls a max of 5.2 amps, you are "supposed" to program the VFD to let it know that...thus only letting it output a maximum of 5.2 amps (by finding out the percentage of the maximum amps your VFD can put out...in this case, roughly 87%), otherwise, you could damage your motor.

What I am not sure about is if you can set your VFD to over 100% in this setting (the amp output). For example: If your motor's max output is 6.2 amps, can you set that setting to 103%? And if so, how far over 100% can you go?

[David DeCristoforo]

Perhaps I should apologize for assuming that everyone who might read this thread would be familiar with the history of this lathe. For those who are not, here is the original thread:

http://www.sawmillcreek.org/showthre...dilemma-quot-)

There are several others as well but they mostly relate to things like the tool rest. Here is the basic motor drive setup I came up with.

http://www.daviddecristoforo.com/Mis...ive_config.pdf

As you can see, there is a jackshaft. The pulley sizes were based on using the dynamotor which has a max RPM of 2400. this will be a bit different with a 1700 RPM motor but the basic setup will be the same.


Now, as to the VFD, I admit to being somewhat in the dark. You can say E=mc2 to some people and they will know exactly what you re talking about. Others will just look at you and say "Ummm… OK,,, whatever you say…" That's me with this VFD thing. If you tell me that I have to program the output amperage and you really mean that you have to set the frequency, I'm going to be confused. I was led to understand that this would work "out of the box" and that the programming was only needed to configure the unit to work with remote controls. Maybe I got that wrong but don't see anything in the manual that says "Before you turn it on you have to do such and such…" The stuff in the manual may be clear to someone who knows what it all means but for me it's mostly incomprehensible. I have some programming settings provided by Dave Muller that have to do with setting up the remote switches but first I need to get the thing working.


For now, it's on hold. I'm waiting to find out why there is no output voltage across the ""T" terminals. I was never able to measure any output at all and that might be because I fried it immediately upon turning on the power as it was not connected correctly. I had the 220 input connected to L1 and L2 when they were supposed to be connected to L1 and L3. That, combined with the fact that it was connected to a 5hp motor instead of a 3hp motor might have been the cause of the malfunction. If so I will just have to eat it. I'll know after FactoryMation get's it back and tests it out.


In the meantime, there is the question of the motor itself. I was not able to run it when I bought it because the seller did not have 3ph available in his garage. But he assured me it was working and offered to refund my money if it did not run. I ill get the motor bench tested in the next few days so at least I will know that much. But because I failed to double check the specs before I bought it, I still have a 5hp motor when I thought I was buying a 3hp motor. Assuming that the motor still works, I will either have to sell it again and find a 3hp one or "upgrade" the VFD to a 5hp model. All in all, this has turned into something of a "sticky wicket", mainly due to my own lack of understanding of the equipment. Next time around I'll know a bit more and I will be a bit more cautious about just flipping the power switch. I'll wait until I fear about the VFD before making any more moves.

[Trevor Howard]

I had the 220 input connected to L1 and L2 when they were supposed to be connected to L1 and L3.

I've installed many Inverters over the years, different brands, but now I am confused DD
Attached is a snapshot from Page 24 of the TECO FM50 Manual

[Ken Fitzgerald]

For the record and clarification,

typically when one uses the term "overclocking" with respect to electronics in general and computers specifically, you are talking about increasing the frequency. In the case of motor controllers, it generally will increase the speed of the motor and in the case of the computer it will do the same.

What Mike is referring to is delaying an overcurrent fault condition. Typically intelligent motor controllers monitor output current and in the event of an overcurrent condition will create a fault shutting down the motor controller. The fault can require a user acknowledgement and input/reset or in some cases it can automatically reset itself while software keeps count of the number of faults for user information.

Delaying over current conditions is often used to provide extremely short periods of currents that exceed the normal overcurrent limits to allow for such things as startup current for the motor or periodic short term power variations generally caused by line voltage variations.

......and for record.....as stated by John.....let's do keep it civil......

This is Ken temporarily in Phoenix.....on vacation.....it's warmer than Idaho was when we left home but not by much.....headed north this afternoon to tour the Grand Canyon later this weekend.

Good luck with your project David!

[David DeCristoforo]

"...but now I am confused DD..."

You are not the only one! That diagram is exactly why I hooked it up as I did in the first place. To me, it looks like the correct connection is the two hot leads to L1 and L2 and the neutral to L3. But then I was told that the two hot leads go to L1 and L3 and no neutral is used. So go figure. Is is any wonder we are confused?

[roger oldre]

do you have the pulleys then? are you sticking to the arrangement in the PDF? your motor is 1725 5hp at this point. center distance plays an important role in both surface contact area and noise. can you approximate the distances?

This lathe was built for several particular operations trying to combine several into one "base machine". I am a production turner. I started in my dads shop when I was 7.



egg 008.jpg

I have used cutting tools from typical chisels to skill saws mounted on the lathe. In my case speed is required.eo]

I have been through this a few times.

Thanks for the backup info it is helpful.

[Trevor Howard]

"...but now I am confused DD..."

You are not the only one! That diagram is exactly why I hooked it up as I did in the first place. To me, it looks like the correct connection is the two hot leads to L1 and L2 and the neutral to L3. But then I was told that the two hot leads go to L1 and L3 and no neutral is used. So go figure. Is is any wonder we are confused?

Looking at the print, I would wire this with the 2 hots to L1 & L2 no connection on L3. The neutral is not needed since its 240VAC Input

[Ken Fitzgerald]

Trevor,

Page 24 IMHO applies to 1/4-1 HP motor controllers and wouldn't apply to David's since his is a 3 HP controller....IMHO....

I could be wrong but I believe page 29 which regards 1-3 HP motor controllers is more appropriate...one must pay attention to the notes at the bottom of page 29.

[Scott Hackler]

Someone smarter than myself needs to explain why a 240VAC circuit doesn't need a neutral. It was alwasy my understanding that a circuit MUST contain a hot leg(s) and a neutral to complete the circuit back to the point of origin (breaker box). .....just trying to learn a few things before I pull wire for a big ole lathe one of these days.

[Ken Fitzgerald]

In a single phase 220 v ac circuit current flows from one hot lead to another. Neutral isn't used. A ground is needed for safety.


In a 110 v ac circuit, current flows from a hot lead to neutral. A ground is still needed for safety in these cases.

Neutral in needed in devices like electric stoves because they use 110 v ac for the clocks while using 220 v ac for the heating elements. A ground is needed that is why most stoves etc. use 4 wire conductors and plugs.. 2 hots, a neutral and ground.

[David DeCristoforo]

"... page 29 which regards 1-3 HP motor controllers is more appropriate..."

The diagram on pg 29 still shows three wires connected to the "L" terminals. Logic, in the words of our favorite Vulcan, would dictate that these would be the two hot leads and a neutral. No?

"...explain why a 240VAC circuit doesn't need a neutral...."

This was my understanding as well. I too would love to hear an explanation for this! Most likely we will get eight or more answers and will end up even more confused!

[Scott Hackler]

Thanks for the explaination Ken.

[Glenn Bird]

DD,
If you read further on page 29, it says that for 230vac single phase, ANY 2 of the three inputs can be used for the 2 hot legs of the 230 volt feed. Shown are 3 connections for 3-phase input power. Therefore you can connect the 2 hot wires to L1 & L2 or L1 & L3 or L2 & L3. Neutral is not required or connected for 230v. ONLY when 115 v is the input power.

[Ken Fitzgerald]

Contrary to common belief, there is more than one method of explaining current flow. The majority of people were taught using the "hole" theory. A few of us were taught the "energy transfer" theory but regardless......

For current to flow in a circuit, there must be a difference in potential between the two inputs.

In the hot legs in 220 v ac, there is a phase difference in the voltages of the two legs and a resultant difference in instantaneous potential. Thus, current will flow from one leg to the other.

Thus, if you were to wire a 110 v ac hot leg to the same, 110 v ac hot leg, there would be no current flow because there is no difference in phase or potential.

However, with an input from a 110 v ac input to neutral, there is a difference in potential and current will flow.