Step down transformer for Porter Cable 7428 to be use in Australia

[addicted2detail]

Hi there!!! I`m Gavin from Australia. Recently I purchased a Porter Cable 7428 Rotary Buffer from the US and so requires a step down transformer. The problem is I do not know how many watts I will needed to do the job. Is there anyone who knows how many watts of step down transformer I needed. I have been told that I need about 10 (Amps) x 120 VAC = 1200watts. Is the calculation correct? Here is the spec: Porter-Cable 7 inches Variable-Speed Polisher

Model 7428

Specifications



Power 120 VAC, 60 HZ Only

Motor Amps 10

No-load Speed 1,000-3,000 RPM

Spindle Thread Type 5/8 - 11 RH

Gear Drive Spiral/Bevel

Wheel/Pad Size 7 inches

Length 17 1/2 inches

Net Weight 8 lbs.

Shipping Weight 9 1/2 lbs.

[Quiksilver225]

Hi Gavin



The formula you found is correct, sorta, but, depends on the current of the input to the rotary. The motor amps maybe 10A, but could need a higher amount due to efficiencies of the motor design. The transformer must supply the input value to the Rotary, not just the end.



Looking at the PC site, it doesn`t tell you anything on the input, does it. Can only guess at what the input should be. 70% efficiency is a fair rate for portable tools. So your 10A at the motor would be 10 x 0.3 losses = 3.3A + 10A = 13.3 x 120V = 1596VA.

Transformers are rated in VA. The next preferred size is 2000VA or 2kVA.

So your transformer you need to buy is 240V primary to 120V secondary, 2000VA. For safety, specifiy 60-0-60 on the secondary so the highest working volts to earth is only 60V instead of 120V.



You will definitly need a registered electrician to wire this setup so you can use the rotary buffer from the transformer.



Note: Because Australia uses a 50Hz supply, your speed range will be 5/6th the speed of the US nameplate speeds. Your speed range is then 833rpm to 2500rpm. A transformer will not adjust this value. It`s possible that this speed might be too low causing the motor to overheat.