1. The documentation
The Toshiba VFD has 300 pages manual and every detail is explained in even greater detail. Its quite exhausting to program the VFD for one that has no idea on what it does exactly. I remember spending a week programming my first VFD. Now imagine the ammount of forums that have to be read to learn the same for the Chinese VFD
Warranty in EU, not China
For a 120eur for the 800w ones for me its a no brainer. However the Chinese one could be interesting in the 2.2-3kw range
Anyways, depends from the point of view. Every machine has critical parts and for me the VFD is one of the most critical. For example i use many of the functions of the said VFD. Like detecting stall and similar and tripping above a pre programmed amperage draw. The enable on my BOB is driven by the VFD. I leave the machine sometimes do long jobs. The machine is powered by 1500w UPS power supply. So if the electricity stops, if the VFD is not connected to the BOB, the machine continues doing whatever it does for half an hour more but the spindle does not rotate, imagine the mess and damage. Sometimes a bit breaks or digs and instead of damage, the VFD trips. i dont know of the functions of the Chinese VFD which possibly are the same. Just like playing safe, at least for a 800w spindle. For my next machine i could also contemplate 3kw chinese kit due to price.
Ok, the seller graciously let me off the hook :-) (lesson learnt - never buy when you're tired & don't trust the Ebay search....get into the detail!)
So ok, since I've now I've been won over into getting a VFD for me 800W water cooled spindle ....the Toshiba in Italy is 0.75KW OUTPUT ...& whilst i'll never upgrade the spindle that I have to a larger one, i do agree with jonathan that it's best to over spec (therefore buy a 1.5kw vfd) because the components will be rated higher & won't break out into a sweat. This leads me back to Chinese ....but there seems to be a huge number out there.
Is there any one particular model that I should seek out? (or avoid?!)
Some VFDs seem to be sent from Portsmouth...which appeals as I'd rather not wait 4 weeks to get up & running on my new machine purchase.
When I was working in industry ABB was always my first choice for drives, I have one on my overhead pin router. I've never used the Chinese ones but there is usually a parameter for switching frequency, not the same thing as output frequency, this can reduce the noise coming from a motor.
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Manufacturers state that its Not OK to oversize or under size VFD . The maximum acceptable is 1 size bigger. I believe its because of trip sensitivity. Obviously 4.5 A rated VFD like the 800W can drive 1500w motor. As 800w spindle consumes 2-2.5A in reality and 1500w motor consumes 4A.
So in fact there is no need at all to oversize VFD as they are strong enough for 10 years non stop use as i remember from the specs. You should check though the manual if you decide to oversize. Need to check if you can program all the parameters of your current motor, like current draw, size, etc. cause what is the point of getting bigger if it could not drive properly the motor you have. Cause i believe certain manufacturers will not permit programming of smaller motor.
Also to avoid further mistakes, find the specs of your motor. Check at what voltage and what frequency is driven! The VFD i recommended you drives 3 phase motors up to 400HZ at 230v. Check if your motor is 200, 300, 400hz or even more and if 230 or more volts. This is very important so you can couple it correctly with the VFD.
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Last edited by HankMcSpank; 07-09-2013 at 10:40 AM.
I agree there's not much point oversizing if you're getting a VFD from a reputable manufacturer - unless maybe it's being operated at an unusually high temperature. You'd be fine with the 0.75kW Toshiba VFD as you'll struggle to draw full power from the spindle, and the worst that can happen if you do is the VFD will just cut out to protect itself. It's better to select the inverter by current rating, not power rating.
The VFDs from China let you set all the relevant parameters, like current and voltage, accurately so there's nothing to worry about there.
Plenty of the 1.5kW VFDs available for £86:
Maybe less if you use best offer...
Last edited by Jonathan; 07-09-2013 at 10:46 AM.
Thats what i was just going to tell. GOOD 2HP 1.5KW VARIABLE FREQUENCY DRIVE INVERTER 220-250V 7A VFD o4 | eBay
The one from his link is 380V and 230v input, that's why is more expensive than the 230V input.
Last edited by Boyan Silyavski; 07-09-2013 at 10:50 AM.
The braking resistor (referred to in the drawing in this advert - HIGH QUALITY NEW 2HP 1.5KW 7A 220-250V VARIABLE FREQUENCY DRIVE INVERTER VFD T2 | eBay ) ....presumably this slows the spindle quicker when the spindle is stopped - is the resistor needed (in other words does the spindle take forever to stop without it)....is it as simple as a large wattage resistor...and what's the spec typically used for the braking resistor? (on the toshiba it said "braking module available separately" ....which suggests it'll cost a pretty penny!)
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