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liaoh75 Wed 31 March 2010 09:08

The money to run them is not that significant if you pair it with an inverter and use only what you need. You will find that if you size your pump correctly with some spare overhead, often times, you'll run your pump at about 40-70% of max capacity and still maintain 11+ inches of Hg.

If anyone is interested, I'd be willing to negotiate a deal with my supplier to ship a quantity of the units here to the states. I'm sure the dealer will give me a good deal on say 10 - 15 units (fixed up, tested, and ready to go) riding piggy back on a container. Just an idea if you guys back home are interested. However, keep in mind that like Brad said, you'll need 3-phase 220 to run them. Also, I'll warn you in advanced, they are not exactly quiet either.

Gerald D Wed 31 March 2010 09:32

David, if you want to regulate the power consumption, you can just open a "leak" to reduce the holding pressure . . . . same effect as a VFD to reduce the speed, but less expensive.

liaoh75 Wed 31 March 2010 09:44

Gerald, that's an interesting idea. I'll give that a try and report back as to the differences. At first I got the VFD for soft start as I got the VFD for about the same cost as a dedicated soft start circuit. I've got a release valve for removing my pieces without shutting down the blower so that will be easy to try. Thanks for the tip!

liaoh75 Mon 05 April 2010 11:08

17 Attachment(s)
Gerald, you are correct. I bypassed the inverter and tested the "spring a leak" suggestion and indeed, the current consumed came down but not as much as using an inverter. With all valves closed, I am pulling about 22" Hg drawing about 29 amps without the inverter. To achieve the same 22" with the inverter, it's pulling about 21 amps.

Using the front four zones (half of my table size), I try to maintain about 12" Hg to make sure nothing will move. Springing a leak without the inverter the pump is pulling about 16amps without the inverter. To achieve the same hold down capacity with the inverter, I only draw about 10 amps. The "pro" to the spring a leak method is that the pump runs cooler with more air flow.

If I measure current after the inverter, I'm reading the same 16 amps but I'm only drawing 10 amps from the breaker???? Can anybody explain how this feat of magic occurs???

Here are some pics I promised.

danilom Mon 05 April 2010 14:52

Great setup David!

But where does that rust on the screws and plate comes from?

KenC Mon 05 April 2010 19:25

I'm not expert but I'll have a go at the phenomena.
As we already knew, an inverter takes in AC power, rectify to DC then choop it up accordingly to make AC of desired frequency & voltage to facilitate speed variation while still maintain the torque characteristic. On the pre-text that there is a fixed relationship between the voltage & the frequency to maintain the torque characteristics, this is why inverters are more efficiency then without. From here, I presume the different current measured is due to the difference in the frequency of the input & output voltace.

lumberjack_jeff Mon 05 April 2010 20:42

Very nicely done.

KenC Sun 14 November 2010 23:30

I was in Taiwan over the weekend & couldn't resist to pay David & his MM a visit.
David flooded me with his warm hospitality & unselfishly sharing his knowledge.
Only had a few hours with him & I was so impressed & intrigued by his work & completely forgot about taking any picture....
I wished I had more time... but I promised I'll be back.... as soon as I can fish a good air passage bargain from AirAsia.
After seeing his rig, I am now totally convinced that a vacuum table speed reduction & vacuum table are not luxurious indulgent...
Now I have to figure out what else can I pawn to get hold of a root blower...

liaoh75 Tue 16 November 2010 10:04

Ken, I am always happy to have you over. Next time, I promise I'll have the camera ready for the occasion. I've been so busy with work over the last several months that I hadn't had much time for or have been too busy to keep this magic of sharing knowledge going on this great forum. Right after you left, I completed that sign you saw leaning on the wall. After the 15mm of acrylic was cut, it turned out beautifully. I will take some pictures of my work and post it here. Stay tuned!

southernduckie Wed 07 November 2012 01:59

Hi David,

just caught up on your post the answer to the VFD reducing the current draw is that it fixes the Power Factor of the motor and draws mostly True power from the mains instead of Inductive power that is drawn by coils of wire aka inductors (like the windings of a motor)
A inductor(motor) will draw power during one part of the Alternating voltage waveform and then feed this back to the mains in another part of the waveform without it actually doing any useful work (ie: wasted current draw) Large industrial sites need to manage this load by installing capacitors at the switchboards or paying extra for there power.
Love your MM truly a well thought out layout.

liaoh75 Sun 11 November 2012 10:15

Hi Andrew,

Thanks for the post. Inverters are still a mystery for me. Thank you for your compliment on my layout; however after a few years building a business (it wasn't easy in my neck of the woods) I find that there were things that could have been done better. We built this when we had minimal funding and was a part time hobby. Gerald's beast is still serving us well today. I'll do a full write-up of all that has transpired since my last post as soon as I can.


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