I was trying to repair my domestic (Sumeet) food mixer(it uses a universal motor). When I opened the back of the rotary switch, which is used for varying the speed, the wires came out before I had an opportunity to notice where they were connected. Please help me put them back......

There are total 4 wires going into the switch.One is the red wire coming from the supply. The other three are orange, blue and yellow and goes to the stator windings of the universal motor.When we turn the rotary switch,one of these wires gets connected to the red wire coming from the supply at a time.The yellow wire has 2 pins connected to it, one directly and the other, through a diode.

Thus, there are 4 positions for the rotary switch,i.e, when the current flows through the orange, blue, or yellow wire directly or through the diode and then through the yellow wire. The rotary switch has various speeds marked on it (0,I,II & III). I need to find out, to which speed the connection to a wire corresponds.

The motor looks somewhat like this:www.globe-usa.com/images/mtrassytom2.gif

As you can see, there are 2 stator coil windings to provide the field. The blue and orange wires split into two on approaching the motor and one of them gets connected to each stator winding, thus connecting the stator coils in parallel, whereas the yellow wire is connected only to one coil- the other coil is connected to the neutral(black) wire from the supply.

Thus, the connections to each stator winding are as follows:

1) yellow, orange, blue

2) neutral wire, orange, blue.

In addition, each of these windings are connected to the rotor through one of the brushes. Thus,when the yellow wire is connected to the supply, the current flows through the first stator winding, then through some wires on the rotor, then through the second stator winding and back to the supply through the neutral wire connected to it. When the yellow wire is connected through the diode, the the rms voltage supplied would reduce to half, as current flows only during one half cycle.

However, when the orange or blue wires are connected, current can flow through the second winding and go to the neutral wire directly, in addition to the path mentioned for the current through the yellow wire. How would this affect the speed of the motor? Morover, I can find no difference in the circuits formed by the blue and orange wires ( maybe, the difference lies in a portion of the motor, which is not visible externally.)Above all, to which of the wires would the zero speed correspond to? This is the greatest puzzle for me.

If you can figure it out, please post the combination of wires and speeds.In other words,

match the following:

0   a)yellow wire through diode

I     b) yellow wire directly

II    c)blue wire

III    d)orange wire

Please read through patiently.Isn't there anyone out there doing electrical engineering?

Also, if someone here uses a Sumeet mixer at home,  please tell me the order in which the coloured wires come out of the switch. I would be greatly obliged.

This is a very good lesson to you..