Grrrrrrrroan - not another VFD thread!

[BobL]

A few quick questions when searching for VFD/motor options.
The VFD I have my eye on is only 240v (single-phase input/ 3-phase output), so I assume that limits motor options to 240v only (no 415v).

In practice yes. A 415V motor may still run on 240V but it won't develop as much power as when it is running on 415V.

Even in 240v 3-phase there seems like confusing number of options from Y to a triangle (is this delta?).

Yes it is delta. Most 240V 3phase motors will be ∆ configured.

Now just to confuse you even more some motors are able to be run on 240V 3 phase (∆ configuration) OR 415V (Y configuration).
This will be clearly stated on the motor name plate like this




To convert between the two the connections at the motor terminal block are changed.
Some info here https://www.woodworkforums.com/showth...ighlight=fasco

[Stustoys]

I reckon 1HP is more than enough on a 9" Hercus. Unless special care is taken, big motors on small machines can create short and long term problems

What if one sets the max amps of the VSD to the amp specs of the factory motor?.....could that give you low end grunt but help prevent overloading at normal rpms?(might be something else for me to test?)

Stuart

[BobL]

What if one sets the max amps of the VSD to the amp specs of the factory motor?.....could that give you low end grunt but help prevent overloading at normal rpms?(might be something else for me to test?)

Stuart

Very interesting and definitely worth a go.
I don't think we really have seen all the possibilities that VFDs provide.
Some techniques/setups on machines may be able to use more power than others so there may be a opportunity to use a bigger motor on a smaller machine with these sorts of restraints otherwise applied.
Have to think about this a bit more.

[jhovel]

What if one sets the max amps of the VSD to the amp specs of the factory motor?.....could that give you low end grunt but help prevent overloading at normal rpms?(might be something else for me to test?)

Stuart

Stu, the answer is 'yes'. If you use a motor with lower power rating than the VFD you SHOULD set the parameter (I think it is P142) to the motor current rating.
If you use a bigger motor than the VFD, you just set the VFD to it's maximum - and that's all the power you can get.
I've just gone down that track with my little lathe: got a 1.5kW VFD and am using a 2.2kW motor. It will only ever be able to draw 7A, but that makes it pretty unstoppable from about 5Hz on - about 144rpm! It still has quite some grunt at 2.5Hz (70odd rpm) as well.
Interestingly, I set the VFD up to test the motor today and the motor seemed happy to run at 150Hz. Never been able to get a 4-pole motor to run that fast. There were no vibrations or funny harmonics (from the fan for example) and the fan is plastic, so I don't expect any major disasters if it flies apart inside its steel cover, inside the thick cast iron lathe base...
I wouldn't be game to try that with a metal fan motor I don't think, but all my other motors pike out around 100Hz anyway.

[Stustoys]

Hi Joe,
In this case I am talking about(for example my 2hp lathe. If I was to change it to a 3hp 3phase motor and VSD. What would setting the motor current to the same as a 2hp motor achive?
Maybe we need a power meter that can handle pwm.

Stuart

[BobL]

Stu, the answer is 'yes'. If you use a motor with lower power rating than the VFD you SHOULD set the parameter (I think it is P142) to the motor current rating.
If you use a bigger motor than the VFD, you just set the VFD to it's maximum - and that's all the power you can get.
I've just gone down that track with my little lathe: got a 1.5kW VFD and am using a 2.2kW motor. It will only ever be able to draw 7A, but that makes it pretty unstoppable from about 5Hz on - about 144rpm! It still has quite some grunt at 2.5Hz (70odd rpm) as well.
Interestingly, I set the VFD up to test the motor today and the motor seemed happy to run at 150Hz. Never been able to get a 4-pole motor to run that fast. There were no vibrations or funny harmonics (from the fan for example) and the fan

Interesting stuff Joe. What sort of current was that motor drawing a 150Hz?

What you were saying about now getting more grunt at low speed and possible probs with fans at high speed maybe another good reason to go with a separate fan.

[Oldneweng]

I have been very interested in reading this thread. I have learned as much from it as from my own recently.

No room for a separate fan on my lathe. Could have been useful. The pump used to supply the centrifuge I operate at work (helical rotor pump) has a separate fan fitted as one of the jobs we do is to fuge juice bottoms, (boubs in French) which are what's left after the clear juice is racked off the top. This job requires the pump to operate as slow as 4Hz as the solids level may be as high as 30%. Possible flow rates are inversely proportional to solids content. There are a number of pumps that are identical except for the fuge adaptations. These are meant to be set to a minimum of 15Hz as they only use the motor fan

Dean

[Stustoys]

I've just gone down that track with my little lathe: got a 1.5kW VFD and am using a 2.2kW motor. It will only ever be able to draw 7A, but that makes it pretty unstoppable from about 5Hz on - about 144rpm! It

Hi Again
Trying again without my 2am brain/tablet typing.

Do the VSDs actually limit current? or does changing the current limit just mean it will trip an error. Or is that something else to test?

Stuart

[Oldneweng]

Hi Again
Trying again without my 2am brain/tablet typing.

Do the VSDs actually limit current? or does changing the current limit just mean it will trip an error. Or is that something else to test?

Stuart

We have a couple at work that will stop if too much current is detected, and display an error message (OC). This is annoying as it can happen at normal running speeds. I guess that they are either set too low or the vfd is not capable of the full power. My guess is the former. I think they pay big money for the vfd's. Generally "Zener" branded I believe. One imagines that the "experts" would know how to install them, instead of putting a sticker on the pump to warn against a current of over 13 Amps. A complete waste of time at this point. Once this error is displayed you have to reset before continuing.

Dean

[jhovel]

Stuart,
My understanding is that the VFDs limit the current to whatever you set it. You can set them to give an alarm and stop or not. I think that's a parameter. Obviously if the VFD has a maximum of - in my case - 7A, but my motor could use 8.5A, it will never see that much current.
The only reason I can see to deliberately limiting the motor current of a larger motor with a lager or matching VFD would be to protect the machine.

Bob,
I didn't check the current drawn by my motor but would suspect it to be quite low, since it was just free running without a belt. I judged the relative torque by putting my shoe on the pulley. I have done that so often over the years, I have a good sense of what a 1/2Hp and a 1-1/2Hp and a 3Hp motor 'feel' like
I'll report what I find in use once its installed.

[BobL]

Bob,
I didn't check the current drawn by my motor but would suspect it to be quite low, since it was just free running without a belt. I judged the relative torque by putting my shoe on the pulley. I have done that so often over the years, I have a good sense of what a 1/2Hp and a 1-1/2Hp and a 3Hp motor 'feel' like
I'll report what I find in use once its installed.

Love it!
I'll have to try it!

[RayG]

I judged the relative torque by putting my shoe on the pulley. I have done that so often over the years, I have a good sense of what a 1/2Hp and a 1-1/2Hp and a 3Hp motor 'feel' like .

Congratulations Joe, you've just got a new nickname... "dyno joe" sort of like dyno-mite

Ray

[jhovel]

Congratulations Joe, you've just got a new nickname... "dyno joe" sort of like dyno-mite

Ray

Thanks Ray.
The only thing is of course that I have no idea what the actual torque is
All I can tell by that method is the relative torque - i.e. if it is running properly or not.
The 3Hp motor in question for example would initially not run over 55Hz, Had me puzzled at first until I 'measured' it's torque and found I could easily stop it. Since you can't stop a 3Hp motor with a shoe on the pulley, the VFD was obviously set wrong - except I couldn't find WHAT parameters were set wrong.
I then did a factory reset (only to find that the factory settings were nothing like the manual defaults) and set each one of relevance to what I had set them to in the first place. Voila, all good. Plenty of 'measured' torque and able to run at 150Hz (I had set that as the maximum). I might see what sort of torque it develops if I go higher - say 200Hz, but suspect A that it won't run much above 150 (too much slippage) and B that it will generate very little torque (not useful).

But I'm also curious about BobL's earlier question and set it to display Amps next test. But first I need to mount it in the lathe. I can't see any way other than from underneath at this stage, which means tipping it on one end, making the motor mount, fitting the motor then tipping it back on its base. That will be fun - not....