Single-phasing a 3-phase motor

[@hochhaul]

Okay now show us what happens when a large 3-phase motor single-phases until it burns up.

[@skylerroskelley423]

Excellent demonstration! Please add the point that, in industry, its very common for loose connections, or arced contact points can cause this and be very misleading. Again, awesome demonstration! Cheers!

[@TradieTrev]

Nice simple theory! I'd love to see a star-delta controller, there's not many vids on youtube with a detailed explanation of its inner working

[@restolad]

that is a fantastic explanation ! I always wondered what was going on when the techs at work said " Its probably dropped a faze " :-)>

[@axdel24]

Please do you have on-line classes ? would love to register and attend ...your explanations are awesome. You make electronics so interesting and easy to follow . Thanks again.

[@cybot63]

That is a three phase motor and if you connect a 600volt 16uf to 24uf capacitor across from the delta third connection that is not powered to one of the live leads the motor will start and will run and reverse if you change to the other live line of the 220volt from the single phase main power feed. you can use two capacitors one for continuous connection and one for faster start ups and the other hooked in parallel with a push button or momentary relay switch. say 16uf and 8uf for the second cap just to keep the motor from heating up on long run times.

[@2raymondle]

I have a 3 phase AC induction motor. But i dont know how to start it up. Do i need a capacitor to start it up? And where can i connect it? By the way, may 3 phase induction motor is a 220V AC. I hope you can help me

[@LouisvilleTorn8o]

Great video! So can you spin a three phase motor by hand like that and make it run on single phase power, or does it have to have at least two phases?

[@sparkyt64]

Here in the US, you typically have either single-phase or three-phase power systems. A single-phase system is called such because there's only a *single* potential. But that's accomplished by having two wires, so the potential is between the first wire and second wires. However, a three-phase system is called such because there are *three* potentials. There's one potential between the first and second wires, another potential between the second and third wires and a third potential between the third and first wires. Sometimes, people will call a circuit with two wires "two-phase", but that's not correct. There is an older power system known as two-phase, but it's extremely rare - at least here in the US. So if you remove one wire from a three-phase system, you end up with a single-phase system, not a two-phase system. Hope that helps.

[@martinarokiyasami3562]

supeer ji....

[@BKD1966]

Well Done.

[@andreaschristodoulou4274]

This can not be true.....and where is your diagram??? by the way this thing can run without capacitors??

[@johnjuma5120]

Three phase motor doesn't necessarily need a capacitor

[@sparkyt64]

This is true. I've been an electrician for 35 years and I've seen three phase motors continue to run several times when one leg of the incoming power has dropped. It's called single phasing. Typically, the motor will slow down and the current on the motor will go up 73%. If not protected properly, this can damage the motor. That's the main reason three phase motors should have starters installed with the properly sized overloads. If one of the legs of the incoming power drops out, the overload will see the increase in current and drop out at least two (usually three) lines going to the motor and the motor will stop. As for the capacitors, three phase motors don't need capacitors because of the fact that there is naturally a rotation field in a three phase system and three phase motors make use of that to start. Since there's not a rotation field in a single phase system, single phase motors need other means to start them. There are several different types of single phase motors. Some use capacitors such as capacitor start, permanent split capacitor and capacitor start/run. Yet others don't employ capacitors such as shaded-pole motors and split phase motors.