WIring arrangements on a ∆∆/Y motor

[BobL]

I posted these pics and some of this info in several threads but I am repeating it here for completeness.

First I strongly recommend not doing this unless you are competent and comfortable with mains AC and motors.
Having the right testing gear is also handy
If this is not you then this is for info only and if needed for you to discuss with your sparky


I found this Tecnomotori 3-4HP motor on a heap of scrap metal. It had no fan, cover to the connection, was a bit rusty, and the rotor was not turning, but as it looked like a reasonably HD motor and I thought I might be able to at least get the bearings out of it. When I opened it up (I had to belt the rotor a couple of times with a wooden mallet to get it out) the bearings seemed fine and the internal corrosion was surface stuff so just for fun I Meggered (checked the insulation resistance) and checked for shorting, and it was all fine so I though I would see if it would get it to run. I put the rusty rotor on a lathe and sanded the rust off. Blew out the dust and reassembled, still Meggering OK, I added an external old 240V computer fan to it, connected it up and it runs - a bit of vibe but no worse than some other motors I have. The end caps were a bit rusty so I tidied them up and gave them a lick-o-paint
http://www.woodworkforums.com/attachment.php?attachmentid=310446&stc=1
In ∆∆ mode its one of the quieter and coolest of my bigger motors in my collection so it's sort of become a bit of a test motor.
It owes me nothing so if I kill it I haven't lost anything.


This motor has 2 sets of terminals and is what is called a double delta/star (∆∆/Y). Sometimes the double delta is called a “serial delta)
Schematics for the connectors are shown in the following diagram.
http://www.woodworkforums.com/attachment.php?attachmentid=310447&stc=1


If power is supplied to terminals 6,4,5 this connects the motor in ∆∆ mode (see ∆∆ in diagram) and it runs at 1490 RPM @ 50Hz and supposedly can deliver 3HP at 415V.
If terminals terminals 6,4,5 are shorted and power supplied to terminals 1,2,3 this creates a Y connection and it runs at 2990 RPM @ 50 Hz and supposed 4HP.


If the impedance (resistance) of any one coil is Z then the resistance between any two terminals in ∆∆ wiring is “4/3 Z" while for Y it is "Z"


I ran it on a 3HP 240V(1P) - 240V(3P) VFD in both ∆∆ and Y modes but as my HP measurer is not finalised I can’t check their power output yet.
The sound/noise/vibe output in Y mode is different - more about that later.
This could be the motor (hardly in the prime of its existence), the VFD or the interplay between the two or the connection mode or interplay between all three.


On some of these ∆∆/Y motors they come with 9 or even 12 wires which enables alternative ∆ wiring.
Just like the 3 wired on common point of a regular Y motor can be disconnected from each other and wired up to separate wires so to can the junctions between the coils at 1,2,3 and 4,5,6.

This is what I was doing in these pics here, it's very difficult to see what's going
Here the junctions (4/5/6) in the schematic (labelled 1/2/3 in the photo) are bing teased out and separated and extra wires added
http://www.woodworkforums.com/attachment.php?attachmentid=310453&stc=1


Everything is sleeved with fibreglass sleeves and sewed back in place
The red, white and black wires are the new wires that go back to the terminal box.
http://www.woodworkforums.com/attachment.php?attachmentid=310452&stc=1

And then either expoxied or siliconed in place
http://www.woodworkforums.com/attachment.php?attachmentid=310451&stc=1


Connections 4,5,6 and 7,8.9 can be the connected up in a variety of ways to create several types of “parallel” ∆ formations like this arrangement which I'm calling ∆1.
It will have a much lower coil to coil resistance (Z/3) so should draw a much greater current and “in theory" produce more power.
In practice there is a fair bit of heat generated and

http://www.woodworkforums.com/attachment.php?attachmentid=310449&stc=1




∆-1 runs at 2990 RPM at 50Hz, so it is no longer acting as a 4 pole motor. It draws about 3-4 times more current (as it should since it is 4 times lower in resistance) and is noisier than the ∆∆ wiring.
The free running current draw and the sound pressure level (dB) will be discussed in the next post. The noise could due to so many factors which I will leave till later to discuss

Here is another wiring arrangement. In theory it's no different to ∆1 but it did not work and I turned it off because above 5Hz the motor was stuttering and making unusual noises
http://www.woodworkforums.com/attachment.php?attachmentid=310450&stc=1

I then put it back into ∆∆ mode to see if it was OK, and it was.

[BobL]

While testing the motor above I checked the noise levels at various frequencies and found the following.

Noise measurements are done in the same location ~1m from the motor using an iPhone running Faber Acoustical App called sound meter. It reads SPL to 0.1dBA but in absolute terms it will be +/- 2dB and more at the top an bottom of its range. I haven't worried about the last decimal place in recording readings.
All results are relative so it doesn't really matter.
These tests are normally tricky to do on a regular motor because the fan speed varies with frequency. However on this motor the fan runs at a constant speed and by itself has an SPL of about 62 dB

The frequency range tested was 20 - 80 Hz for the Y and ∆1 since these were already running at 2990 RPM @ 50Hz

The ∆∆ connection is clearly the quietest especially ay intermediate and higher frequencies - as low as just 2 dB above the noise of the fan.
It was still running very smoothly at 120Hz
The free running current for this is around 0.4A except at 60 - 70 Hz where it is 0.3A

The Y seems to have a resonance at 50Hz - sorry didn't check the free running current for this.

The ∆1 is noisiest at around 30Hz and has a free running current of between 1.1 and 2.0A with no real pattern to what is going on.
The increased current is to be expected as the resistance of the combined coils will be much lower than the ∆∆ wiring.
Hopefully this will also produce more power.

I need to bear in mind that this is a fair beat up motor so most of what I'm seeing could just be the crappy motor.
I would be interested to hear others interpretation of what might be going on.
I will also test some of my other motors.

What I really want to do is test the HP available from each wiring arrangement which I hope to be able to do as soon as my HP measurer is complete.

http://www.woodworkforums.com/attachment.php?attachmentid=310455&stc=1

[DavidG]

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[Old farmer]

BobL, thank you for a very interesting contribution. You lost me when you got on to the electrics but I admire your skills.
And thank you for the great photos.

[BobL]

Cheers OF.

Just for comparison - although it's hardly a fair comparison, below is the SPL v frequency from another 3-4 HP ∆∆/Y motor (from my linisher)
The TM lines refer to the Tecnomotori motor experimented on above while the LG refers to the Linisher motor
This of course has a fan and most of the noise, especially at higher RPMs. comes from the fan.

BTW the VFD driving these motors also has a fan and that has an SPL at 1m of 55dB.

The fan clearly dominates the sound output of the LG motor.
At low RPM the LG fan (in both ∆∆ and Y) is hardly turning over so it is quieter that the TM fan.
AT higher RPM the LG fan is loud but the TM fan stays the same
This can be seen if the LGY data (bright blue line) is corrected (frequencies halved) for RPM and replotted which then generates the orange line which can be seen overlays the purple line which is the LG∆∆ line.

These experiments need to be done without a fan but clearly they cannot be done for too long without damaging the motor.
That's it for a while I have other things I urgently need to do.


http://www.woodworkforums.com/attachment.php?attachmentid=310467&stc=1

[BobL]

Here is another ∆∆/Y motor I delved into yesterday.
This is the LG motor from my linisher that I refer to in the noise tests above.
It's real name is ElectroADDA which I will abbreviate to ED

The ED was a bit easier to access that the Tecnomotori, and because the connection wires are different colours, a bit easier to work out what is going.

Here you can see the common Delta points.
http://www.woodworkforums.com/attachment.php?attachmentid=310698&stc=1

One wire from each of the common points is split off and connected to a new wire (blue black, tan) and taken back to the connection box.
Here it is all stitched back together - I'm getting quite quick at this now.
http://www.woodworkforums.com/attachment.php?attachmentid=310699&stc=1

An siliconed down
http://www.woodworkforums.com/attachment.php?attachmentid=310700&stc=1

Here is what the connection box looks like
http://www.woodworkforums.com/attachment.php?attachmentid=310697&stc=1
The LHS terminals are the (9-4. 7-5, 6-8 referred to below) ∆ connect pairs, and these are in tern connected by the brass strips to their respective Y terminals 1,2,3 on the RHS

http://www.woodworkforums.com/attachment.php?attachmentid=310449&stc=1

[BobL]

I have the ED motor back together (I decided to give the motor housing a bit of tidy up and quick respray) and it is running nicely in parallel delta mode at 2990 RPM @ 50 Hz.
There's one thing that bugs me and that is a small vibe at 25Hz that wasn't there before in either Y or ∆∆ mode.

Anyway, now that I have all the connections all out at the terminal box I can always (re)configure it how I want.

Now I need to stop mucking about with motors and get back onto finishing that linisher

[lamestllama]

Here is another wiring arrangement. In theory it's no different to ∆1 but it did not work and I turned it off because above 5Hz the motor was stuttering and making unusual noises
http://www.woodworkforums.com/attachment.php?attachmentid=310450&stc=1
I then put it back into ∆∆ mode to see if it was OK, and it was.

Hi Bob I think what you were trying to do in ∆2 is this455134which by my understanding of the windings should produce a 4 pole motor.

[lamestllama]

BobL

I have modified my Colchester Bantam two speed motor to allow me to run it as either two pole or 4 pole with a VFD.

I am considering the pros and cons of each configuration for final fitment to the bantam switching between two speeds set on the VFD.
I can either run it as a two pole motor at 50hz and 25hz or as a four pole motor at 100hz and 50hz.

I am tending towards the two pole configuration for the following reasons.

The motor It is rated at 2hp at 2800rpm and 1hp at 1400rpm from this we can deduce that the torque of the motor is the same in both configurations as power = C x rpm x torque (for some constant C).

The two pole motor run at 25hz will rotate at 1400rpm and should produce the same torque as it does at 50hz thus should produce 1hp this is the same power output as the motor originally produced in 4 pole mode at the same rpm thus the cooling fan should be sufficient.

I wonder what your thoughts on this are?

[BobL]

BobL

I have modified my Colchester Bantam two speed motor to allow me to run it as either two pole or 4 pole with a VFD.

I am considering the pros and cons of each configuration for final fitment to the bantam switching between two speeds set on the VFD.
I can either run it as a two pole motor at 50hz and 25hz or as a four pole motor at 100hz and 50hz.

I am tending towards the two pole configuration for the following reasons.

The motor It is rated at 2hp at 2800rpm and 1hp at 1400rpm from this we can deduce that the torque of the motor is the same in both configurations as power = C x rpm x torque (for some constant C).

The two pole motor run at 25hz will rotate at 1400rpm and should produce the same torque as it does at 50hz thus should produce 1hp this is the same power output as the motor originally produced in 4 pole mode at the same rpm thus the cooling fan should be sufficient.

I wonder what your thoughts on this are?

Makes sense. Don't forget that power produced is related to applied load. The main danger from overheating is trying to push the motor too hard but this happens at any rpm.