HOW TO IDENTIFY ACTIVE and GROUND WIRES OF AN INDUCTION MOTOR 5

[newbie18]

Hi guys! I am working on an automation project. I want to switch on/off (using a relay that requires connection to COM and NO/NC terminals) an induction motor that would spin fan blades. My problem is that I do not know the wiring of the electric motor. I opened the conduit box, and it only contained white and black wires. I want to know which of the wires is the V+ and the ground.

The specifications of the electric motor are as follows:
Mindong YC-80B-4 1/2hp 220V 4.5A 60 Hz Continuous Rating Electric Motor

Thanks!

 

[ScottyUK]

If it follows convention then white is neutral and black is the phase conductor. The motor is an AC machine and the concept of '+' is meaningless.

Neither the black nor the white wire is a ground, which is a separate conductor and typically coloured green. This installation doesn't appear to have a ground. The missing ground is almost certainly a code violation. Frankly the whole installation looks to be in dangerously poor condition, and from the questions so far I'm not certain you have the knowledge to make it safe.

 

[itsmoked]

The conduit is non-conductive so even it is not providing the needed safety ground. It's a capacitor start, capacitor run motor.

I too suggest you find an able electrician to help put things straight. Note the cable grip been ripped out of the supply box and there is a hideously bad zip cord also lacking any strain relief running into the box - probably the reason someone ripped out the flex grip.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Skogsgurra]

I can only second what Scotty and Smoked say.

You got one thing right, though: your nick. This indicates that you are willing to learn. But don't start learning on an object that can kill you or someone else.

Get an electrician to help you out. Anything else is illegal.

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[petronila]

Hi Newbie 18,

Like all said this is an AC electric motor, this one is single phase and works with 220 ac V.

If you want to switch on/off the motor cut the power.

Use a contactor with one 24 DC Volts coil and control the power of the coil with the relay. You should need a single phase transformer (220/24) and one rectifier to get the 24 DC Volts.

Regards

Carlos

 

[newbie18]

thanks for answering!

petronila, is there a much simpler way? I want control the relays using Arduino. Thanks.

 

[waross]

If you want simple, throw out the Arduino and use an HP rated toggle switch.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[zeusfaber]

HP rated toggle switches can be a legitimate part of an automation project, provided your budget includes a little bit of funding for a post-doc student to operate them.

Here's your design constraints:

The Arduino output is limited to a few volts dc - and not a lot of current.

This is absolutely not enough to drive your induction motor.

It is enough to drive a small relay (look through the product range of any Arduino supplier and you'll find a selection of relay modules, complete with built-in interface circuits).

The sort of relay you can drive with an Arduino is almost certainly not big enough to switch your motor (induction motors are nasty loads which draw large currents on starting and generate large voltage spikes when shut down. Neither feature is kind to relay contacts). As Petronila recommended, the way to get round this is to switch the motor using a contactor - a high power relay specially designed to withstand the horrors inflicted on it by a motor load.

You are unlikely to find a contactor you can drive directly from the Arduino, but you should be able to switch power to it using an Arduino-driven relay.

If you choose your components carefully, you should be able to work with:
[ul]
[li]Arduino (and its power supply)[/li]
[li]Relay module for the Arduino (and its power supply - it will need one to drive the onboard interface circuit. Choose carefully and you will be able to run the relay module off the same supply as your Arduino). Make sure the relay is rated to handle mains voltages and has a current rating several times the current drawn by the contactor coil - coils are another nasty load. A relay module that offers "opto-isolation" between the input and the relay is vastly preferable to one which doesn't [/li]
[li]A contactor with a 220V ac coil and contacts that exceed your motor rating.[/li]
[/ul]
Program and wire the Arduino to drive the relay. Wire the relay contacts to switch a 220V mains supply to the contactor coil and use the contactor contacts to switch the 220V mains supply to the motor.

For all that this "control driving relay driving contactor driving load" daisy chain arrangement may sound a bit cobbled together, it is exactly the way that many industrial motor control panels are designed. Draw it out, and you'll find it's less complicated than it sounds.

A.

 

[itsmoked]

And, if you switch to the Arduino make sure you hang a LARGE obvious sign on or near your motor warning that it could "automatically turn on". Also make sure you don't let the Arduino turn it on and off more often then every 5 minutes.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[newbie18]

Again thanks for answering my questions.

petronila and zeusfaber, you're the best! driving the contactor (or another relay) using an arduino relay module was also the suggestion made by my friend. However, I do not know how to wire an arduino relay module to the contactor (or another relay). Can you help me on that matter? Thanks.

As of now, I connect the contactor to the induction motor and it is working, my only problem is wiring the relay to the contactor.


Attach below is the picture of my problem. Thanks in advance for your response! Have a good day.

 

[zeusfaber]

That Arduino relay module looks familiar - the one I have on the desk in front of me is its 8-relay big brother.

You've got the contactor-motor arrangement working at the moment? So somewhere, there's a switch you presently work to make the contactor switch on and off? You should find it wired in series with the contactor coil. Assuming you can find that, disconnect it (at the switch end) and connect the resulting pair of wires to one of the relays.

How? Each relay has three screw terminals associated with it. Connect the wires to the two outer terminals (which way round makes no difference) and leave the centre terminal empty.

Top tip: Get the Arduino programmed and working with the relay module properly (so you can see the lights on the relay module going on and off, and hear the relays clicking) before you wire the contactors into the relays - troubleshooting is so much less stressful when you haven't got machinery running wild all around you.

A.

 

[ScottyUK]

However, I do not know how to wire an arduino relay module to the contactor (or another relay). Can you help me on that matter?

I have to ask - is this the level of competence which we should be encouraging to work with power circuits, especially ones which are obviously in disrepair?

I hate to discourage anyone from trying to learn, but I'd rather do that than encourage anyone to hurt themselves through lack of understanding. Newbie18 - consider finding a smaller motor capable of operating from a low voltage supply until you get familiar with the principles. Once you get to grips with the basics then think about moving on to higher powered stuff.

 

[newbie18]

Thank you all for your input.

 

[IFRs]

Cut the green wire. NO !!! Cut the red wire. AUUUUGGGGGHHHH