VFD Testing using Incandescent bulb load 1

[prysm]

Hi all

Can I use incandescent bulbs to replace the motors for preliminary VFD testing?
I used to be able to test inverters using incandescent bulbs as load. I was told that I can do the same with VFD's, I also remember reading something similar here. I can't find the thread now. So I wondering if anybody can confirm this approach is at least feasible. At least untill I get a bit more experience with VFD's

thanks
prysm

 

[Skogsgurra]

You sure can. But do not try Vector Control, a bank of incandescent lamps does not have much in common with a three-phase induction motor. So, switch to scalar mode. Done that soo many times, no sweat. It is actually quite instructive to run at frequencies around five Hz and watch the rotating system "walk" around the lamps. Arrange them in a triangle for best visual effect.

Gunnar Englund

http://www.gke.org

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Half full - Half empty? I don't mind. It's what in it that counts.

 

[jraef]

Test them for what though? Basic functionality? Yes. Performance? No.

"Will work for (the memory of) salami"

 

[itsmoked]

Be careful. Do it only in deep secrecy with shutters drawn. Don't let anyone catch you with evil incandescent death-bulbs.

Our lawmakers prefer you use CFL bulbs for this.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Skogsgurra]

Yes, Keith is right. I apologize for not thinking about the legal implications. OTOH, not so sure that CFL will work. But better unsafe than illegal - don't you think?

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[itsmoked]

No.

I'm a firm believer of 'what's right' verses 'what's mandated by idiots'.

On the other hand it would be interesting to see how long the CFLs lasted...

Keith Cress
kcress -

http://www.flaminsystems.com

 

[jraef]

I predict not long enough to emit useable light. Those things take too long.

"Will work for (the memory of) salami"

 

[Skogsgurra]

Time to do some serious scientific testing!

I got so tired of waiting on my CFL bulbs that I will happily kill them softly with - not a Soft Starter - but a VFD.

Stand by for RWSR!

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[ozmosis]

I can see a mushroom cloud over Sweden...

 

[prysm]

jraef

Just basic functionality. I want to learn about VFD. Things have slowed down at work that I have some time learn something new. Is there a way to test VFD performance at the bench level without a motor maybe an AC load?

regards
prysm

 

[Skogsgurra]

Lamps (incandescents) are OK. Keith and a few of us are just kidding. You will get lots of fundamental insights when running with lamp load.

Then, if you measure voltage across the lamps with different multimeters, you will learn about the problems associated with measuring PWM. And, if you have the time and possibilities, build a simple 1 Hz low pass filter and measure the output from it. Very instructive. And your initiative is very commendable.

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[jraef]

The motor, being an INDUCTIVE load, becomes an integral part of the full benefit of using a VFD. Performance in an AC motor involves torque, so the only "AC load" I can think of that involves torque will be a motor. The lightbulb test is, as Gunnar says, interesting and a good cheap place to start to learn about how a VFD functions at a basic level, but that has only a limited relationship to its full potential.

However if you can get hold of ANY small 3 phase motor, you can run it with the VFD and get an appreciation for the richer rewards it has to offer. Even if the voltage and/or the size of the motor is significantly different (within reason), it's still very informative for learning not only that potential, but also the limitations. I once picked up a 3 phase 460V 1/2 HP motor off of the sidewalk for free after nobody bought it at a garage sale, I used it for years to test ideas with VFDs in 230V and 480V applications, keeping cognizant of the issues and limitations. I used it quite a bit to teach people these issues. I eventually sold it to someone who needed that exact motor, now I recently went on-line to find another one and scored a 3/4HP 230V 3 phase industrial blower someone was selling for $10, now I even have a load this time! The point is, keep your eyes peeled for any kind of 3 phase motor deal/trash, it's more common than you might think. If you are in the US, do a search on your local Craigslist site and just use the search term "3 phase", you might be surprised.

"Will work for (the memory of) salami"

 

[prysm]

When I was working on a simple inverter design. I was able to beg a vendor to let me borrow an electronic ac load. I was able to load my inverter full load, half load etc. I was able see how it behaves dynamically. Is there such an "electronic load" for VFD?

 

[Skogsgurra]

I cannot see how that would work.

You can easily make a motor/centrifugal fan combination change load by restricting flow. Use anything - a couple of plywood sheets that you cover the air inlet with is simple and flexible.

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[itsmoked]

Use a motor AND the light bulbs for extra visual information if you like.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[mikekilroy]

nice idea itsmoked. we do same with the db resistor AND 8pc 100 watt bulbs in series around it on the repair bench to see that circuit work.

http://www.KilroyWasHere<dot>com

 

[itsmoked]

Hi Mike! Oh yeah the breaking resistor!! That would be really informative adding energy flow direction info.

Keith Cress
kcress -

http://www.flaminsystems.com