# Questions tagged [three-phase]

AC power with three legs run 120 degrees out of phase

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### Switching a 3 phase pump using a solid state relay

I made a remote (GSM) controlled module for a 3 phase pump close to my friends house. The pump should run at night, and walking the 1km to the switch while they are sleeping is the problem. The ...
221 views

### Circuit for switching higher load using transitor with signal being 300 Hz PWM

EDIT: DO NOT even think about using the naive example of a circuit to switch three phase. As someone rightly pointed out this is a complex issue and will almost certainly result in burnt finger or ...
73k views

### 3-phase explanation

I have been reading about single phase and three phase power. I'm completely confused now. Can someone please give me a working example of when I would use three phase power instead of single phase (...
1k views

### What is the current limit on each phase of a 160 kVA three-phase UPS?

I'm a physicist by training, so I think I understand voltage, current, phase and power. However, I lack the knowledge to translate between this and the published ratings on three-phase electrical ...
1k views

### Unknown motor, specifications interpretation and use

I got a motor on the picture. Does anyone know what it was used for? My main question is if is it feasible to use it as a barbecue motor or is it too strong? Can I connect it to one or three phases ...
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### Can we remove the neutral wire?

If we have the connection shown below (star connection of the secondary part of a TX), the load per each phase is equivalent (balanced load), then the vector sum of ...
2k views

### How can i measure voltages on each phases of a 3 phase system, Using a microcontoller?

How can i measure voltages on each phases of a 3 phase system. The measurement is to be processed by a microcontroller. Is there any special chips available, or do i need to use the ordinary ...
4k views

### How does a three-phase transformer work with phases sharing a common core?

Google search reveals a lot of pictures of three-phase transformers. Looks like a common setup is to have three pairs of winding and a shared core. The core typically consists of three "bars" in ...
23k views

### What causes unequal phase-to-neutral voltages in three-phase distribution systems?

A four-wires cable runs into an apartment building to supply it with three-phase 380/220V alternating current. Each apartment is connected to one phase, different apartments are connected to different ...
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### Shortcircuited motorcycle alternator leads to RPM proportional losses?

I've had this puzzle for a couple of years but never been able to figure it out. Regulator manufacturers for typical 3-phase alternators provide the 14.4V by 'shorting' the phases. Obviously this ...
2k views

### High power three phase ac motor controller

I have come across this question a lot in the design of a special 3 phase motor controller I plan to build this summer and I think I need to ask it directly to solve it. I need to be able to ...
71k views

### Why is three-phase offset by 120 degrees?

For three phase electricity the wave is offset by 120 degrees(2$\pi/3$ Rad). Why aren't the phases closer together? Is it because it will affect the frequency of the phases? How was this 120 degrees ...
11k views

### 3-phase Motor Speed Controller

Background If you look at my profile description, you'll see that I'm involved in building and wiring up Carnival floats that are powered by an 800KVA, 415v, 3 phase Generator. Electrically, they ...

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