Tuesday, 12 July 2016

Before buying a Chinese drill machine /Tear down a Chinese drilling Machine.

Today , I have received a faulty Chinese drill machine for repairing. I do not want to disclose the brand name here. It was of 800 watt,220 volt,50hz.costs around INR 1500.
As usual I opened the casing .And found that that the field winding is partially  burnt due to overheating. It was a winding short circuit issue.
It provides many features but the technology and the quality of material is very poor.

The most strange thing is its sped controller .Common Good branded drilling machines usually uses phase fired controller to control the universal mot6or speed. This method is little bit costly .
But this drill uses only a 500ohm resistor for controlling the armature current thus speed . It is now clear that It has only two speed stages, you can not vary speed according to your choice.
As it uses resistor, It spoils power as head.
Armature Quality is not also good.
One Good feature is that you can reverse the direction of motor rotation if needed. It does this by reversing the brush position.
It does not have any EMI and harmonics filter. A DC series motor produces too much harmonics and fed it to supply mains. So it has an adverse affect on other sensitive equipment running parallel in your home.
Here I have drawn a circuit by investigating its connection. It will help you during repairing.

So ,I recommend ,Don’t Buy this type Of drill Machines.