3 phase relay control

Hi,

I am new to this forum so would like to say hello to everyone and thank you in advance for any advice given.

Firstly I am not a qualified electrician but I have a deep understanding and if like to think I have common sense hahaha!

My idea is I have a 3 phase motor and a 415v three phase supply. I am making a motor reversing electronics device to control the motor direction and turn it on and off. I'm going to use relays for each phase line. My question is could I use a 230v 10amp rated relay for each line as that is all that will be on each line?

There are contactors (direct on line starters), designed to do exactly what you want. They actually amount to two separate contactors in the same box with a mechanical interlock to ensure both cannot engage together. This is essential for safety as any failure in basic relays doing the job would put a direct short between phases or reverse the supply whilst the motor was running.

as above, the proper devices for what you want already exist and are easily available

Have a look here

I'm sorry I don't think I made it clear in my OP

I will be controlling this with a 3.3v logic controller. I can't seem to find any DOL online with this function. Can anyone share a link please?

I don’t think you’ll find a DOL starter that can do what you want without some form of interface.

Ok.

I think it'll just have to be relays with overload protection in case of a short then. There will always be someone monitoring the running of the motor anyway and I can't imagine that would be a very cheap option.

Would 240v relays on each line be ok? So overall 6 240v relays to run forward and reverse?

Have a look at these, the only problem is the minimum control voltage.

http://uk.farnell.com/sensata-crydom/d53tp50d/ssr-50a-4-32vdc/dp/1200208

PS they aren't cheap.

Yeah thats not cheap at all. Well out of my budget.

Would 240v rating be sufficient if i had 6 single SSR's for 415rmsV?

One thing you have to bare in mind is the motors starting current, it could be anything between x5 to x8 FLC. The IC has to be able to handle the maximum peak load.

Why not use a standard starter & just design the interface?

This is diy for Home use not for use in a business though yes?

Yeah the motor is only 600w so it will never be above 10amps I would have thought with th? Its around 1amps FLC so 10 amps should do fine unless you'd think otherwise?

I'll have full isolation from the HV to LV side via optocouplers for safety so the person using the LCD dispay controlling the IC doesnt get zapped as well as an MCB.

For goodness sakes don’t get involved in HV 230V can kill a healthy adult in fractions of a second, HV will likely kill you & do the cremation at the same time!

I wish it was that simple. I have a rotary draw pipe bender that i have made and I am sticking an encoder on the main shaft to measure 5the rotation/bend angle. The encoder will be read by the STM32 IC board and the input of the required bend will be input into an LCD Screen and started by pressing go usining this interface turning the forward pin high. Once the encoder signals the required bend the the IC will pull the fwd pin low switching off the SSR's and the waiting 1 second and the running the motor back the user defined degrees to release the pressure to allow the pipe be removed.

Yes its a DIY project.

OK sidewinder i'll just use a peddle bike and gearing instead of an electric motor.

I wont lick the terminals i promise ROTFWL

So are you messing around with HV or not?

It’s DIY, but you are suggesting HV how, what?

i think his HV is LV and his LV is ELV

Yes it's HV 415v 3 phase controlled by a microcontroller circuit at 3.3v

I have a 3 phase supply in my garage

400v is low voltage

The legal definition of LV, MV & HV isn’t really the problem, the problem comes with the OP’s competence and his ability to work safely. That is out of our hands.

Before SW jumps on me, I know MV isn’t recognised in IEC countries but it’s generally accepted elsewhere and is a useful demarcation.

Well the original question did state it was 415v and not one of you have answered any questions I've asked yet?

Can I use a 230v relay on one leg of the 3 phase line? So if I want to switch on the motor in the forward direction I can switch on 3 240v relays for the 3 legs?