# 3 phase power supply detector.

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#### yusuf

##### Member
How should I detect whether 3 phase AC line is available or not..

I have a motor pump which needs 3phase AC power supply to run..

I want to add a indicator (via led) which can detect the absent/present of 3 phase power supply.

#### dougy83

##### Well-Known Member
If you are expecting all phases to be on, or no phases to be on: a neon/led (w/ series resistor, led with protection diode) between two of the phases - that will tell you that at least one of those 2 phases are available..

If you are expecting some of the phases to be available while others are not, then that seem a bit strange to me...

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#### yusuf

##### Member
If you are expecting all phases to be on, or no phases to be on: a neon/led (w/ series resistor, led with protection diode) between two of the phases - that will tell you that at least one of those 2 phases are available..

If you are expecting some of the phases to be available while others are not, then that seem a bit strange to me...

As the motor tuns on 3phase AC line..
I want to detect the 3phase and then run the motor else motor will not run in the absent of 3phase..

It will only run if the 3phase ac is available..

#### yusuf

##### Member
sorry unconditionally double post was posted..

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#### dougy83

##### Well-Known Member
So does that mean you expect that some of the phases will drop out?

If that's the case, you can connect a line voltage sense optocoupler (any run-of-the-mill bi-directional input one should do) between each of the phases in a delta configuration, and wire the output transistors in series. The transistors will conduct only when all 3 phases are present, which can be used to turn on your LED.

#### yusuf

##### Member
thanks dougy very much...
But if you can give a schematic then I can understand properly..

#### dougy83

##### Well-Known Member
No, I can't provide a schematic at the moment. I can send one after I get home, or you can try to understand the following words. The configuration is extremely simple:

There's 3 Bidirectional-input Optocouplers. I will refer to them having an input 'diode' and an output 'transistor'

The input diodes are connected to the 3phase power source in delta configuration.

The input diodes will need a series resistor to protect them from overcurrent.

The output transistors of the 3 opto couplers are connected in series.

The series-connected output transistors provide the switch for your indicator.

#### yusuf

##### Member
ok...
so just simply can you create in paint ... with rough diagram..
because I dont understand some things like : delta configuration etc..

#### dougy83

##### Well-Known Member
Delta configuration.

Each resistor shown in the attached diagram will have an opto coupler input in series with it. The points of the triangle (X,Y,Z) are where each of the 3 phase power is connected

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#### yusuf

##### Member
what will be the values of resistor...

#### KeepItSimpleStupid

##### Well-Known Member
I've used stuff from this company http://symcom.com/ with very good success. Take a look at the voltage/phase monitor demo on the right hand side of the page.

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#### yusuf

##### Member
Delta configuration.

Each resistor shown in the attached diagram will have an opto coupler input in series with it. The points of the triangle (X,Y,Z) are where each of the 3 phase power is connected

again , what will be the values of resistor..

#### dougy83

##### Well-Known Member
again , what will be the values of resistor..
What is the peak phase-phase voltage (Vpp)? What is the peak allowable current through the opto input (Ip)?

The resistor value will then be $R\approx\frac{V_{pp}}{I_p}$

#### yusuf

##### Member
What is the peak phase-phase voltage (Vpp)? What is the peak allowable current through the opto input (Ip)?

The resistor value will then be $R\approx\frac{V_{pp}}{I_p}$

How should I find out , what is my peak allowable voltage..
I just know that I have 3phase power supply...

So next what should I'll have to do..

#### dougy83

##### Well-Known Member
How should I find out
You can look it up based on your country. Try google.

#### yusuf

##### Member
You can look it up based on your country. Try google.
Ok I have the following configuration in India :

Single phase: 230 V, Three phase: 240/415 V

#### dougy83

##### Well-Known Member
415 is the phase-phase RMS voltage, so the peak phase-phase voltage is ~590V

#### KeepItSimpleStupid

##### Well-Known Member
There has to be commercial phase protectors available in India. They are really common in the US.

Generally I used them to protect EXPENSIVE stuff like a $5,000 USD roots blower and protecting devices such as Cryochillers such as this one: **broken link removed** It was also used on some 3 phase vacuum pumps. An aprox$100 USD device was very worth much it. It easily fit into the relatively large motor control disconnect, overload relay and contactor. Later, the overloads were replaced with solid state units when they failed after 15-20 years.

If your lucky, the solid state overload relays will have built in 3-phase protection so the extra box isn't required.

#### yusuf

##### Member
There has to be commercial phase protectors available in India. They are really common in the US.

Generally I used them to protect EXPENSIVE stuff like a $5,000 USD roots blower and protecting devices such as Cryochillers such as this one: **broken link removed** It was also used on some 3 phase vacuum pumps. An aprox$100 USD device was very worth much it. It easily fit into the relatively large motor control disconnect, overload relay and contactor. Later, the overloads were replaced with solid state units when they failed after 15-20 years.

If your lucky, the solid state overload relays will have built in 3-phase protection so the extra box isn't required.

I dont want phase protector ...

I just want to create a circuit which can just indicate the availability of 3phase line. via turning on/off the led.

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#### yusuf

##### Member
Will this circuit be modified to detect 3phase...

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