Step down transformer

[marcus9x9]

Hi,

I recently bought two motorized Dremel 6000 contour sanders from USA.
The operating power stated on the sander is 120V 50-60Hz 1.15A

I live in Malaysia. The household power rating is 240V 50Hz up to a max of 13A.
I used a new 500W step down transformer to power the sander.

The step down transformer steps 240V down to 120V. It is an auto-transformer, with only one winding.
The transformer output shows 120V when measured on a multimeter.

The 1st sander operated for about an hour before it failed. I did not operate it continuously for the entire hour but rather few minutes each time. I disassembled and assembled the sander and it operated again but not for long before it failed again just after a few minutes. I disassembled the sander and checked the resistance of every coil and found out that one of the coils is open. There is no way it will operate until the coil is rewind.

The 2nd sander operated only for a few minutes before it failed. I dismantled the sander and checked the resistance of every coil and all look good.

The sanders is built in with an adjustable speed controller. The input power is connected to the controller before it reaches the coils.

Can an auto-transformer cause this problem?
Can a difference in frequency (50 vs 60) cause this problem?

Thanks for looking.

Cheers
Marcus

 

[johnboy6083]

a difference in frequency will cause the motor to run faster (Ns = 60f/p). i dont know if this would cause the motor to burn out , but it might be a contributing factor to the faliure of your appliance

 

[marcus9x9]

The frequency here is 50Hz which is slower than in the US.

 

[davelerave]

you should be ok i reckon

trafo is well rated and sander is 50/60hz

odd

hope you didn't step-up with the trafo?

 

[marcus9x9]

No, I did not step up with the transformer. Even measured the output with a multimeter to be sure it is 120V.

 

[davelerave]

i know you didn't

nothing obvious to me anyhow i'm afraid

 

[marcus9x9]

I have attached pictures of the sander disassembled. The electronic adjustable speed controller is also shown.