Remote start up and three phase

[Jimmy Mack]

I'm looking at switching my start/stop on my 3ph extractor for a DOL... So I can put in a single phase remote....3 pole contactor with 240v coil

Looking at the motor connection/ terminal panel it (the motor) has four wires, when I was expecting three, L1,L2 &L3....(& gnd of course)... My feed up to the existing (sealed) start /stop is L1, L2, L3 (&gnd) ... Tho the other side of this sealed start/stop is producing a four wire connection. Is this some kind of balance?

Jim [emoji848]



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[9fingers]

So the extra wire is connected to the delta point at the motor end?

Trace the other end of that wire to find what it does. Possibly nothing or just maybe there is some need for a local neutral. Is there an agitator motor to rattle the filter perhaps?
More info needed

Bob

 

[Jimmy Mack]

Hi Bob,

No filter agitator or anything, just a plain old fan.

I'll try and get inside... In the meantime a few pics...

Rotary isolator, standard stuff... Three lines in, three out to the starter on the clear Flexi swa

Three lines into my starter, which appears to be sealed, even behind the label I can't see a way in [emoji848]

And the fan motor terminals, receiving four from the starter

I've had a look over the motor for a spec plate, but no further info

Jim

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[9fingers]

Given there are no other bells and whistles on the machine, then I suspect the fourth wire is a normally closed thermal switch connected to one of the phases inside the motor. If the motor gets hot the switch opens and acts on the nvr coils to turn off the supply.
Theses thremal switches only operate at low current and therefor it is vital that we find which of the four wires are the three high current phases and which is the low current thermal switch.
This cannot be done by simple voltage measurements alone
You are going to have to do some investigation. Do you have a multimeter (DVM) capable of measuring ac current to say 10 amps and know how to use it?
Maybe post a photo of your meter?

Bob

 

[Jimmy Mack]

Ah right, I see, is it a (cheaper) similar intention as having a thermal overload relay, to detect high continued current draw, failing fielding/ winding, too high load etc?

Or a thermostatic switch for overrunning or fan air flow/ cooling restriction?

My brother has the multimeter, I'll have him bring it over.

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[9fingers]

Ah right, I see, is it a (cheaper) similar intention as having a thermal overload relay, to detect high continued current draw, failing fielding/ winding, too high load etc?

Or a thermostatic switch for overrunning or fan air flow/ cooling restriction?

My brother has the multimeter, I'll have him bring it over.

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Yes this method which measures elevated temperature once the motor has got hot rather than checking the current draw as is done in a proper DOL starter. It is the cheap and nasty companion to the nasty NVRs that are creeping in on chinese sourced machines.
In your proposed new solution I suggest that you use a proper DOL starter as the starting point for your remote control and you will get decent protection.

I will draw a diagram later to show how to make the measurements to show which wire is the thermal switch. Normally black, brown and grey will be the high current wires leaving blue for the switch but we need to confirm this properly.

Cheers
Bob

 

[9fingers]

ok here is the diagram of what I expect is in your motor.


you will be making measurements on running equipment at three phase voltages.
These will bite! take great care!
Method:
Set meter to measure >500 v ac.
Start the machine
Probe between each of the 4 incoming cables.
Most will read 400v but just one pair will be virtually zero volts
This pair will be the thermal switch
Call these A and B
Configure the meter to read 10amps AC (NOT DC)
Stop the machine and make permanent connections to the meter in series with point A.
Start the machine and record the steady current.
Stop the machine replace the connection to A and insert meter in the lead to B.
Start the machine and record the steady current.
The lead that has virtually no current flowing will be the temp sensor. You wont need this in the new scheme. Cut the wire off from the imcoming cable.
The other three will be the high current feeds to the motor.

Use just these three to your new DOL switch

Bob

 

[Jimmy Mack]

Thank you Bob for taking the time to write this up, I'll try this soon.

Is the second test to record the current draw... Essentially belt and braces, confirmation?

Jim

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[DaveL]

Thank you Bob for taking the time to write this up, I'll try this soon.

Is the second test to record the current draw... Essentially belt and braces, confirmation?

Jim

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Its not belt and braces, you need to find which wire of the pair is carrying the motor current, as you need that one connected, while the other 'sence' wire will be disconnected.

 

[9fingers]

yup Wot he said!

thanks Dave

Bob

 

[Jimmy Mack]

yup Wot he said!
thanks Dave

Bob

It was getting late.

Ok, here we go...


My A&B



Running Flow & Full Load Amps




'A' is my sensor then, shall I just disconnect it and put it on a blank terminal block ?


Jim

 

[9fingers]

HI Jim,

When you are ready to fit the new remote switching system leave the A wire connected to the exisiting terminal block at the motor end and put a little note in the box saying what it is for the future.

Then when wiring up the new switch snip off the A wire in the cable in the box leaving 3 wires plus earth used.

Similarly snip off the a wire at the far end of the motor cable.

Bob

 

[Jimmy Mack]

Thanks Bob, and thanks for helping with the diagnostics [emoji16]

I'll have a look into the switch next week, before I isolate the thermal sensor.

My plan is to connect a 240v remote to a 3 pole contractor with a 240v coil.... Doesnt look like Toolstation can help this time, though I might use the old/ new Toolstation DOL box* to house a contactor I've seen in Screwfix... Along with a thermal relay.

How do I calculate the required cut out Ampage... It must be somewhere around 5.5 - 6A?

(*Contractor pinched to fix Planer thickness)


Jim

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[9fingers]

Thanks Bob, and thanks for helping with the diagnostics [emoji16]

I'll have a look into the switch next week, before I isolate the thermal sensor.

My plan is to connect a 240v remote to a 3 pole contractor with a 240v coil.... Doesnt look like Toolstation can help this time, though I might use the old/ new Toolstation DOL box* to house a contactor I've seen in Screwfix... Along with a thermal relay.

How do I calculate the required cut out Ampage... It must be somewhere around 5.5 - 6A?

(*Contractor pinched to fix Planer thickness)


Jim

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The tool satan one will do what you want just select 240v coil. All their contactors are three pole and rated for three phase voltages.

95364 plus 89114 should do nicely

Bob

 

[Jimmy Mack]

That's handy to know.... There's very little product information on the website

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[9fingers]

That's handy to know.... There's very little product information on the website

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I agree. I only know cos I use them quite a lot. Very good value for money

Bob

 

[Jimmy Mack]

I've Google found a PDF manual for the extractor! ....And in it is a schematic :eusa-doh: , see below! I don't know why I didn't do this before. Though it's been a useful exercise me.

The reason for the manual search was to try and get some info on the motor rating ( no spec plate) to calculate the required thermal overload. Looking at some websites I'm getting a little confused by the maths involved :? .

Is there a rule of thumb? Perhaps 10% over the Running Ampage of a line and allowing for 50% on another line behind? Based on one of my lines being 3amp (max running ampage read ), would a sensible cutout setting be 5 amps?

The motor is 2.9KW 50Hz

There are some details on the switch, though I'm not sure if they are specific to the motor and switch or just the switch itself.


Apologies if these are rather simple questions

 

[9fingers]

I'd not realised that it would have such a beefy motor. the low running current confused me.
2.9kw is almost 4 hp.

Thermal overload relay should be set for the full load current and ideally that should sit in the middle of the adjustment range but this is not always possible depending on what is available.

Full load current on a three phase 400 v star motor is around 1.7 amps per hp (2.3amps per kW) so 6.5-7amps for your motor.
Your measured figure was quite a bit less I think and this could well be to do with lower friction in your ducting compared to the maximum the extractor is designed for.

The thermal relay is there to protect the motor and the motor should be happy with drawing 6.5-7 amps so I'd go for the 31837 relay 5-8amps. Set it at minimum for now and be prepared to tweak it up a bit if you are getting nuisance trips.

hth
Bob

HTH

 

[Jimmy Mack]

Thanks Bob, I almost opted for the lower rated relay. Knowing that my 3.3kw Sedgwick planer cut out is set to 6.5A (ref manual) thinking that it, the PT will likely experience higher loads than the extractor fan... Though if all my extraction gates are closed maybe not.

To be fair the manual (see pic) isn't helpful as it also lists the motor at 3hp, so I went with the higher Kw rating.... So perhaps it is 3hp and the Kw are wrong? [emoji848] ... (Regarding your original thoughts on it's size and current pull, tho this could also be the low load of the fan)

The physical appearance of the motor *is* rather large. Though this is probably a poor indicator.

Thanks again,

Jim

Edit. Ps...my machine is column, far right

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[9fingers]

P1 is the input power and P2 the output power.

Note that the difference is not implying huge inefficiency in the motor but a mix of some waste heat output and power factor.

My 1.7 amps pwer hp is a figure to cover both rating ie an input current for an output horsepower.

So your full load current will be in the region of 5.1 amps and so use the next lower thermal overload that I first suggested. Furthermore it makes your running current measurement more likely too.

Bob

 

[Jimmy Mack]

Up and running [emoji846]http://cloud.tapatalk.com/s/5c9a19f49745a/VID_20190326_122019662.mp4

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[Jimmy Mack]

Probably added a couple of pounds to the waist line.

.

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[9fingers]

Looks the part Jim!

Just as a check, you did remember to wire the coil in series with the output contacts on the thermal overload relay?

I only mention it because many people think the overload relay it self contains switches to disconnect the load.

This is not the case. It contains current sensors that open an isolated contact pair when over current is detected.

Cheers
Bob

 

[Jimmy Mack]

Ah... Have I gone wrong?....I tested the trip and it switched off [emoji848]

I'm breaking my 240 live

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[Jimmy Mack]

My coil supply comes in at 96 and out of 95 (down left hand side) to A2

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[9fingers]

My coil supply comes in at 96 and out of 95 (down left hand side) to A2

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That is Spot On Jim exactly as it should be. We will make a sparky of you yet! :lol: :lol:

Bob

 

[Jimmy Mack]

My coil supply comes in at 96 and out of 95 (down left hand side) to A2

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That is Spot On Jim exactly as it should be. We will make a sparky of you yet! [emoji38] [emoji38]

Bob

Woo!!!! [emoji41] Time for a proper job! [emoji16]



From checking continuity...I'm assuming the pair on the left are for sounding an alarm or lighting a warning lamp, be as they appear to be normally open and close on trip.

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[9fingers]

From checking continuity...I'm assuming the pair on the left are for sounding an alarm or lighting a warning lamp, be as they appear to be normally open and close on trip.

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Spot on again. I can see I'm becoming redundant round here :lol:

Bob

 

[Jimmy Mack]

From checking continuity...I'm assuming the pair on the left are for sounding an alarm or lighting a warning lamp, be as they appear to be normally open and close on trip.

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Spot on again. I can see I'm becoming redundant round here [emoji38]

Bob

I doubt it [emoji38]...

I've learnt quite a lot from this thread/ project and about motor control in the past year, saving myself £100's.

This switch is a great addition to the workshop, something I've be thinking about for over two years... Can't believe I've been in here that long!

Cheers, Jim

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