Yet another three-phase motor question

Hello all. Having read several of the related threads I'm pretty well confused about inverters, converters, static and rotary means of providing 240v 3-phase from domestic mains supply. Perhaps one of you gurus will be kind enough to point me in the direction of most cost-effective solution to the following problem.

I've acquired a benchtop sliding table saw with a LeRoy-Somer motor, type LST 71 69, of the following spec.

kW 0.55, ch? 0.75, rpm 3000, 50 Hz

I've moved copper links to change it from star (v420, A 1.25) to delta (v240, A 2.2) as given by the motor plate, and now need the means to feed it. Is a VFD, with the potential for speed variation, a better bet than some other device giving just a fixed speed ? I think single speed would be acceptable for my needs, though one never knows.

Your words of wisdom will be much appreciated, and sorry if I'm asking you to repeat advice already given to others,

thanks,

Ken

Hi Ken. Most VFD's if not all will give you speed adjustment. Once you set the speed you can just leave it at that setting. Just use the on and off buttons and it does not alter. You probably will not use the reverse feature. Depending if you are using it for work or pleasure will determine whether you go for a cheap Chinese VFD or a High cost Chinese VFD. I use cheap Chinese VFD's from Ebay on my mill and lathe and have had no problems over the last couple of years. They only cost about £90 each. Once you match the motor to the VFD its usually simple from there on.

regards

For £90 and 0.55kW you could get a proper VFD from a UK supplier. You might get lucky with a Huanyang VFD but they are a long way from being an industrial product, having seen inside them myself.

Murray

Murray,

I'm looking at upgrading to a modern VFD, as I would like Vector Control. Thanks for the link. I was impressed by Inverter Drive Supermarket, the easy start guide they produced for the LS Starvert iC5 1.5kW was excellent. They also have manuals for all their products, and the prices look competitive.

John.

I'm rather partial to Yaskawa myself (sometimes badged as Omron). Their VFDs come as either J1000 (simple V/F control) or V1000 (vector control). Obviously the vector version is more expensive - I suspect it has an additional DSP inside it. They are proper industrial drives that have been proven in all manner of applications, as you can see from the comprehensive manuals.

Be aware that many of these VFDs come without an EMC filter. Many people don't bother but ideally you'd get the recommended one. With the Yaskawas, the factory option is supplied by Schaffner so they aren't giveaway cheap. However, the VFD piggy backs on the filter, giving a neat installation.

Murray