4 or 5 pin plugs for 3 phase supply from inverter?

[pgrbff]

I have recently bought a 3 phase bandsaw for hobby use and acquired a single phase to 3 phase inverter to power it.
When I looked at buying cable and plugs/sockets for the supply I didn't know if I should choose 3P + earth or 3P N + earth plugs and sockets.
What is the difference and which should I buy?

 

[ipf]

I have no problems wiring the inverter but I have never used 3 phase.
This is the junction box on the saw and how I believe it should be re-wired. But I am confused about the neutral?
I can buy 4 pin or 5 pin ind plugs/sockets and I just really wanted to know which I should use and why.

Totally called for, it seems.
If you don't understand it, DO NOT mess with it.

If you're determined to, get information first hand...... and face to face from someone qualified to offer it.

 

[Steviec1]

Totally called for, it seems.
If you don't understand it, DO NOT mess with it.

If you're determined to, get information first hand...... and face to face from someone qualified to offer it.

Your motor is wired star, you will need to wire it in Delta. 3 pin supply plug.
In case you were thinking of it, it is not good practice to wire from an inverter to a motor via plug and socket.
It will be better to get a 4 pole 20A isolator with an auxiliary and wire the 4th pole and auxiliary back to the inverter enable signal.

 

[Mike Johnson]

And wired through a NVR switch.

 

[pgrbff]

Totally called for, it seems.
If you don't understand it, DO NOT mess with it.

If you're determined to, get information first hand...... and face to face from someone qualified to offer it.

So you have someting against me learning? the only error I seemed to have made so far is not appreciating that I need screened cable between the motor and inverter. Luckily, by seeking help, albeit socially distanced, i discovered before ordering.

 

[James]

So you have someting against me learning? the only error I seemed to have made so far is not appreciating that I need screened cable between the motor and inverter. Luckily, by seeking help, albeit socially distanced, i discovered before ordering.

Learning is good and should be encouraged,
However, it is difficult for us to understand the entire setup you are planning with the limited information provided.

Perhaps you could post a drawing of how you intend to set this system up.
Just a simple block diagram, we still dot know where in the system this 4 or 5 pin plug is intended to be fitted.

Converting a 3phase machine to single phase is not as simple as putting an inverter inline on the supply cable and changing the motor configuration.

There are serveral other things to consider.
Some have been mentioned but not replied to.

You have mentioned that it must be screened cable from inverter to motor, this may or may not be the case.
It depends on make and model of inverter
Distance of cable run between inverter and motor
Proximity to other cables and equipment

As mentioned before, consideration needs to be made for replacing the original contactors and control gear that is likely to be the wrong voltage and not suitable for being powered by an inverter

Many inverters are Simpley not suitable for running off a domestic socket because of emc filtering, dc leakage, start up surge etc.

 

[pgrbff]

Learning is good and should be encouraged,
However, it is difficult for us to understand the entire setup you are planning with the limited information provided.

Perhaps you could post a drawing of how you intend to set this system up.
Just a simple block diagram, we still dot know where in the system this 4 or 5 pin plug is intended to be fitted.

Converting a 3phase machine to single phase is not as simple as putting an inverter inline on the supply cable and changing the motor configuration.

There are serveral other things to consider.
Some have been mentioned but not replied to.

You have mentioned that it must be screened cable from inverter to motor, this may or may not be the case.
It depends on make and model of inverter
Distance of cable run between inverter and motor
Proximity to other cables and equipment

As mentioned before, consideration needs to be made for replacing the original contactors and control gear that is likely to be the wrong voltage and not suitable for being powered by an inverter

Many inverters are Simpley not suitable for running off a domestic socket because of emc filtering, dc leakage, start up surge etc.

You are right, and maybe the most important factor is that none of you know me or my capabilities.
Warning someone to be careful is one thing, "funny" comments like "I can smell a bit of 'boom boom' in the air." are not to my mind useful at all.
I was advised to use screened cable by the inverter supplier who has been incredibly helpful. But he is in England and I am in Italy. I had originally intended to not hardwire the saw to the inverter for the sake of maneuverability, but wiring plugs with screened cable is not worth it on balance.

 

[Lucien Nunes]

Let's wrap up the plug thing then...

3-phase motor never needs neutral, therefore 3P+E (4-pin plug) is OK. (FWIW all our machines in the workshop are connected to the mains with 3P+E plugs, none needs a neutral)

BUT

Motor is inverter-driven. Shielded cable has been recommended. Inverter is part of machine drive, not a general source of supply of 3-phase in the workshop (both kinds exist), therefore better to have motor wired directly to inverter.

Inverter might generate significant earth leakage current on its single-phase input. Ordinary domestic plug and socket outlet might be OK for current rating but not permitted for high leakage loads due to risk of accidental loss of connection. I can't remember the limits on earth leakage imposed by the CEI. It would be preferable to use a blue 2P+E plug and socket to EN 60309 rather than either Schuko or 'type L' / Forza / CEI 23-50 S 17 16A.

Next... what about machine controls and braking? What method of braking did the saw have, what is required by your local regulations, and what are you providing it with?

 

[pgrbff]

Let's wrap up the plug thing then...

3-phase motor never needs neutral, therefore 3P+E (4-pin plug) is OK. (FWIW all our machines in the workshop are connected to the mains with 3P+E plugs, none needs a neutral)

BUT

Motor is inverter-driven. Shielded cable has been recommended. Inverter is part of machine drive, not a general source of supply of 3-phase in the workshop (both kinds exist), therefore better to have motor wired directly to inverter.

Inverter might generate significant earth leakage current on its single-phase input. Ordinary domestic plug and socket outlet might be OK for current rating but not permitted for high leakage loads due to risk of accidental loss of connection. I can't remember the limits on earth leakage imposed by the CEI. It would be preferable to use a blue 2P+E plug and socket to EN 60309 rather than either Schuko or 'type L' / Forza / CEI 23-50 S 17 16A.

Next... what about machine controls and braking? What method of braking did the saw have, what is required by your local regulations, and what are you providing it with?

I'm happy with stop-start, no speed control. There are several wiring options in the manual.
The saw is probably more than 60 years old so no braking. I considered braking and a resistor is available. Someone I know said he had problems with resistor braking, it caused the invertor to go into alarm. It may just have been the ramp was incorrect. I'm going to try it without brake and go from there.
The earth leakage may be a problem, I'm not sure what type of RCD I have on the circuit that feeds the room. The area where I will be using the saw isn't wired yet but I was considering using someting along the lines of img below.
Thank you for your help.

 

[ipf]

So you have someting against me learning? the only error I seemed to have made so far is not appreciating that I need screened cable between the motor and inverter. Luckily, by seeking help, albeit socially distanced, i discovered before ordering.

It seems you've got it all sussed, then...

As Lucien indicates, if you're plugging an inverter into a domestic socket for a 3 phase output, it's asking for trouble, especially if, as in this case, the inverter is not part of the motor control.
Looking to change a CU, I came across a 'home business' example. A bloke running a 3 phase lathe, making specialized model railways. The lathe had it's own inverter.
I didn't know why the RFC loop impedance readings were up the wall, until I found it, upstairs in his 'workshop/spare bedroom'.

 

[ElectroChem]

I'm happy with stop-start, no speed control. There are several wiring options in the manual.

A motor inverter is not suitable for driving a DOL switched motor. The inrush current will at the least trip the inverter and likely damage it. So you're already looking at needing to modify the control circuit for your saw.

We're still waiting on that block diagram James asked for. We're a varied and talented group here, many of us convert and modify machines on a daily basis, but we can't help you unless you quit dribble-feeding information and work with us.

 

[pgrbff]

The control connections will be used for on/off, i just don't require speed control.

 

[Mike Johnson]

For safety sake whatever you use connect it through a NVR switch.

Merry Christmas by the way.

 

[ElectroChem]

I give up. In response to a specific request for more information we get a one line answer long on confidence and entirely lacking in detail.
I'm no longer convinced the OP is even an electrician, given their initial open ended query about 'how do I choose between 4 and 5 pin plugs' and their thread history. As such, I cannot entertain helping a DIY machine modification of this scale. It's a cliche on this site, but seriously, get an electrician. And not a house-basher, you need someone with machine controls and motor experience.

 

[pgrbff]

I give up. In response to a specific request for more information we get a one line answer long on confidence and entirely lacking in detail.
I'm no longer convinced the OP is even an electrician, given their initial open ended query about 'how do I choose between 4 and 5 pin plugs' and their thread history. As such, I cannot entertain helping a DIY machine modification of this scale. It's a cliche on this site, but seriously, get an electrician. And not a house-basher, you need someone with machine controls and motor experience.

You made an assumption about how I would wire the on/off. Sorry, you assumed wrong.
I'm not an electrician. Just looking for some advice. Feels to me that some find it more rewarding to knock people down than offer help.
You might like to consider that some people have enquiring minds, they like to understand why something is done in a particular way, for their own benefit.
You might also like to consider that it is not unknown for a professional to offer poor advice. I would like to know a bit more before I decide on a solution.
Hapy Christmas

 

[ElectroChem]

Here's this professional's advice, be your own judge of whether it's good or poor.
Your reticence and demonstrated lack of subject knowledge mean you're not capable of doing this on your own. We've offered you all the help you could want, and you've thrown it in our teeth.
Be off with you.