Transformer for 2.2 KW chinese spindle question?
I bought a 2.2KW chinese water cooling spindle with 2.2 KW inverter VFD. I don't have 110V supply. So I need a step up transformer (110V to 220V) that can supply enough power for motor and VFD without blowing up itself. I consider to buy a 3000W transformer but it recommend at least 1.5 times greater than the equipment power. Is it ok to buy 3 KW transformer to use with 2.2KW?
here is the link of the transformer:
http://www.amazon.com/Goldsource-STU-3000-Voltage-Transformer-Converter/dp/B0022U0MSQ/ref=pd_ybh_4]Amazon.com: Goldsource STU-3000 Step Up/Down Voltage Transformer Converter - AC 110/220 V - 3000 Watt: Electronics
Thanks.
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You mean you do not have a 220v outlet where the table is going. Every where in the USA has 220v going to their house or business. Personally I would find someone to run a 220 v line to where you have your table. Which would still give 110v also.Originally Posted by bao84
I'd assume the VFD itself will use more than the motor's rated 2.2kW, so a 3kW transformer might not be big enough. Anyone with more experience in this subject, please correct me if I'm wrong.
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Well here is where I see the problem will be is at start up of the spindle. Will be pulling more amps 2.2 kw = almost 3 hp which is about 9.7 amps running under load. 3000 w which is 15 amps from the wall. now figure the start up surge. Will be close to over the convertor rating for a few seconds. Now this is all at full speed. Now all this figured with out any losses in the convergences from 110 to 220 transformer. Here is the bad point I can not find any specs on the convertor on the net. Like input amps(wattage) to output amps (wattage). The only thing shown is 3000 watts is this for 110v then is 220v 1500 watts is only. Power convertor, inventor, and some of the cheaper generators companies have all used the largest number in their description of a product. Which can be very misleading to the average persons.
You do not transform wattage, IOW if it is rated for 3kw on 120, then it still has a 3Kw capacity when transformed to 240.
The current capacity will drop accordingly.
IOW on 120v x 25 amps = 3Kw with 240v x 12.5 amps = 3Kw the current capability drop as a direct ratio.
Also an Induction motor on a VFD does not have the inrush its direct fed counterpart does
The VFD can be tailored for a suitable acceleration and current rate.
Al.
CNC, Mechatronics Integration and Custom Machine Design
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.
I have been running a 1.5kW wood lathe with a Schneider Electric vector VFD for years on a 2 kW transformer from 110V. No problems. There is an inrush when the VFD is turned on to charge the internal caps. But the transformer just gives a short hum. Accelerating the motor may draw the rated power but not more since the current is limited.
Lately I ran a 240V line and got rid of the transformer for convenience.
The VFD is quite efficient at full power so I would expect a 3kW xformer will do O.K. with a 2.2kW spindle.
As I understand a motor will draw max current at start up at full speed without the VFD (I might be wrong). In my case, I use VFD to start the motor, so I assume as long as I start the motor at half of its full speed I should be fine with 3KW transformer right?
Correct.
At the point of switch on, a 3ph motor is effectively a transformer with a shorted turn secondary.
You can use full rpm, just tailor the max current and acceleration rate in the VFD to suit.
If the Current is set too low you may get nuisance tripping.
Al.
Last edited by Al_The_Man; 11-30-2012 at 10:54 AM.
CNC, Mechatronics Integration and Custom Machine Design
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.
did you mean set the current on VFD to suit the max current of the transformer (not the max current of the motor)? For example, let say transformer output at 220V 13.5A, so I should set the max current on VFD about 13A.
Transformers are pretty rugged items, if it is rated at 3Kw, it will take momentary O/L with no effect.
Also the 3Kw consumption is very likely not going to be continuous.
IOW, the motor is not going to be running continually at max HP.
Monitoring the heating effect over a normal running period will be an indication if the transformer is stressed.
Al.
CNC, Mechatronics Integration and Custom Machine Design
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.
Thanks Albert. I'm going to buy a 3KW transformer and test it out.
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