EMD is all around us

Sometimes unexpected things happen. When I came back from Christmas vacation I was surprised by a non-working baking oven. What a great time for something like this to happen? – I thought in the first place. But what can you do sometimes? So, I called my house caretaker, made a fault report and got an appointment with a service company.

This week, finally this service company arrived and in a rather quick repair of maybe 10minutes they exchanged the motor for the fan and the series connected heating element since they burned due to a defect of the motor. Fair enough, as someone who works on fault tolerance I had to fulfill my duty and kept this machine for some analysis. This one here, had no fault-tolerance at all obviously.

So, let us have a closer look. My oven is connected via a three-phase plug, so theoretically, it could have been a proper AC-machine. This here is however an universal machine. Basically a DC-machine where the excitation and armature winding a series connected to make it work with one-phase AC. The type of power coming out of a regular plug.

The two connections at the bottom are the two electrical contacts. Also, the excitation winding is wound around the stator iron. It is underneath the tape and around the brown plastic bobbin. The rotor and the armature are not really visible because the mounting in the upper half covers it.

Well, why this machine then? The main reason here must be the cost, it is simple and does not cost a lot to produce as there is not that much. I can count the number of laminations per hand and they are not even glued, as the staples indicate. One winding is cheaper than three and being able to operate directly from a normal wall outlet is a major advantage. Actually, basically all home appliances run on some variant of this machine. So, the next time you grind your coffee, blend your smoothie or vacuum clean, you know what is making the blades spin.