Universal Motor AC and DC
17/07/2022 | Views: 602 | Circuits | by: ELECTRONOOBS      


What’s up my friends, welcome back. I've took this motor from an old washign machine and this is called an Universal motor since it works with both DC and AC voltage. It has a lot of wires adn might be difficutl to know how to wire it up. In this post I'm going to show you how this motor is inside and what would each wire do, then I will show you the connections and how to control this motor with both DC and AC power. You can get such a motor from here as second hand.



Part 1 - How it works


Ok, so as you can see below, the motor is just as any DC brushed motor but it has no permanent magnets. It creates the S aN polarity magnetic field using other set of coils connected to the stator. These coils are fixed in place. By passing current through these coils, they create a south and north magnetic fields, just as some permanent magnets. Then, just by applying voltage to the brushes, as with any other DC motor, it will start rotating and conmmutating the voltage applied to the rotor coils using the brushes and the copper conmmutator. It wirks with AC as well because since it doesn't have permanent magnets, and it uses coils to create the magnetic fields, using AC we can also do that. But AC is osciallating, so it will change the magnetic fields just wehen is needed to keep the motor rotating. Permanent magnets can't do that so that kind of motor wouldn't work with AC. Pretty easy right?

Universal Motor Wire connection AC DC




Part 2 - Wires


When I've took the motor out, it had 7 wires. Which one is wich? Well, using the multiemter we can find that we have two connections to a tachometer used for measurign the rotation speed for the washing machine. We don't need that in order to control the motor, only if you want to precisely control the speed. Then we have two other wires. These two are for the left and right brushes. Finally, the last 2 or 3 wires are for the stator coil. Sometimes we have 3 because we also have the middle connection between the coils whcih are connected in series. So, how to wiere this up in order to make it work?

Universal Motor 7 Wire connection wirting


Part 3 - AC DC Connections


Well, since we have to supply both the coils and the brushes at the same time with the same voltage, we need to connect them in series. So we apply positive to one brush. We exit on the other brush and we connect that to the left coil for example. From the left coil we have an internal connection in series with the right coil. So we exit from the right coil and we go to the negative connection of the supply. That's it. This works with both AC and DC.

Universal Motor washing machine wire connection




Part 4 - AC Dimmer


For the final part I've used a simple circuit for an AC dimmer to control the power applied to the motor using AC voltage. THe circuit I've used is the one below. Is very simple using a TRIAC and a DIAC and a few passive components. Make sure you use a heat sink for the TRIAC if you control lots of power. You can also buy one from HERE which will work a lot better.

Universal Motor AC Dimmer circuit TRIAC


Part 5 - Watch full video tutorial


So guys, I hope you now know how an universal motor works and how to cntrol it. Check all the connections above adn the full video below. If my videos help you, consider supporting my work on my PATREON or a donation on my PayPal. Thanks again and see you later guys.





17/07/2022 | Views: 602 | Circuits | by: ELECTRONOOBS      












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