1949 3hp/3ph 575rpm/Yaskawa VFD/Tonkin-L350 noise filter.....?

M

Mr.20c

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Hello,
I am a new member here, I was sent a pm from a member over at CNCzone to come here and check the forum out. I Like what I see so far....

So here is the dilemma I am having....

I have a Moak 32" band saw from 1949 with a Master Motor (3hp/3ph - 575rpm,13.7 amp) I am using a Yaskawa VFD with a 19.5 amp rating on the 3ph output to run the motor (the drive was designed for 230 single phase in) . I was concerned about the age of the motor and the rep from precision zone recommended a noise filter, the Tonkin-L350 if I did not feel comftorable and was worried about spike voltages hitting the windings.

I have only used the saw 2 or 3 times since i brought her into my shop and everything was fine and worked Well. I am in the process of completing a restoration on her and I took of the rubber tires and wanted to clean off all the old glue. I ran the VFD at 3hertz for the frequency setting to run it slow so I could scrape all off the old glue/adhesive off the wheel with a steel chisel.
I noticed this funny electrical smell, couldn't figure out were it was coming from then I put my hand on the Tonkin and nearly burned my hand. There was some clear liquid coming out of the top, very little,a few drips so I imediatly shut it off.

My question is, why would it heat up like that and do I really need the Tonkin -L350 noise filter? I took it off the machine and ran it directly from the VFD to the Master motor for a few minutes with no issues running it at 3hertz just to check the heat on the motor the motor was still cold, not even warm.....
Is it really necessary to have this filter in there? I was just concerned because of the age of the motor/windings.


Any thoughts about this, what exactly happened to heat the L350 up like that and what was the clear liquid coming out? Do I really need the filter? I ran the band saw at a full 60hertz when I used her before and never had any issues....

I am thinking of omitting the L350 from the setup ....should I not do that. I have been getting mixed opinions on this....?

Thank you,

Brian
 
It depends on where the filter's fitted - if it's on the input (AC line) side, then most filters are suitable (current rating notwithstanding), on the motor side it *must* be designed for the purpose, all the motor side filters I know of are purely inductive and may be described in the blurb as "line reactors" - their main job is cancelling the VFD to motor cable capacitance to ensure stability in the VFD's output devices and reduce the effect of switching spikes on the motor's insulation - particularly important for older non-VFD-rated motors and long cable runs.

If the filter between your VFD and motor is designed for the AC input side has capacitors in it between the U,V and W phases, it *will* overheat and *could* trash the VFD as the cap's will be absorbing anything up to 1200V spikes... that might be why they're leaking!

I googeld for Tonkin, couldn't find 'em - is it a Tokin filter? If so, only their KA and KB (inductor only) filters are suitable for between a VFD and a motor

Just my ha'pennorth,
Dave H.
 
Tonkin L350
I had it between the drive and the motor running at 3hertz for cleaning the wheel. When I ran it at 60hertz I never had a problem. What would cause the L350 to overheat...... :thinking:

Is it worth having the motor rewound to modern standards? I am having some reservations on putting L350 back on because of the excessive over heating at low frequency setting.



B,
 
Spelling error on my part, you are correct, Tokin . Specs are on page 16: http://www.nec-tokin.com/english/product/pdf_dl/noisefilter_e.pdf

States max voltage drop/voltage hertz drop: (50) then from the drop list it states 1.5?:thinking:....I would surmize that the VFD set at 3hertz would constitute a voltage drop? Little confused about this?:huh:

I am not an electrical engineer, I am a wood craftsman ......so please don't throw mud at me....:lmao:



What do you think?:thinking:


B,
 
OK... If they sold you that (on P16, an *input* filter for 3-phase supplies) to go between VFD and motor, They Messed Up! That's OK for the supply side but not for the motor side, as it has capacitors in - these are being hit with spikes at *much* higher than the 50 or 60 cycles that it's built for, and will try to absorb most of the VFD's output power, which looks like interference on a 50 or 60 cycle line - this is why it gets damn hot, most of the 3HP is being dumped into the filter, not the motor!

If you compare the diagrams for the 2 types (bottom of P16 and top of P20, KA and KB series) you'll see that the KA/KB don't have the capacitors - shown as parallel plates in the diagrams. The capacitors are the VFD killers, and what are absorbing the power and getting a bit warm!

If you look at page 18, the LF series for inverters, it specifies either the KA series for 200V line or KB for 400V line - if your VFD's fed with 220V, the KA series should be right - the LF-320KA is a bit tight on the spec' (20 A current rating, your motor rating is 14A), so it'd be best to go with the LF-350KA (50 Amp rated) between your VFD and motor if it's within budget. Of course, if you go to 'em saying they could have fried your VFD by giving you the wrong filter, you're a bit cross, they might forget about any price difference - hell, the KA filter might even be cheaper!

Hope this makes sense,
Dave H.
 
Thanks Dave,
It,s 220vlt VFD . I looked at page 20 on the schematic, I see what you mean, so these are just coils then with no capacitors. And these coils will prevent the voltage spikes on the windings of my master motor?



I am thinking of just omitting the filter. Can't I coat the windings On the motor and avoid this filter alltogether? I was looking at this product, http://www.glyptal.com/Glyptal_Product_Data_Sheets.htm what do you think?

I am trying to get a grasp on what happens to the motors windings when spiked , are they moving, do they have a potential to rub against one another causing a short, why is it that inverter duty motors don't have the risk in damage as I am having with this motor, is it the winding size, coating,...etc...etc...:thinking:


Thank you for helping me get to the bottom of this. That's what happens when you go from wood to electricity..:huh:



Look forward to your response,


B,
 
The motor Isnt designed to run at low speeds.. The motor is designed to cool itself, which at 3hz your not moving the motor fast enough to cool itself, you are overheating it running that slow.
 
Bruce,
When I was s scraping the wheel, I did that for 40-45 minutes and the motor was not even warm, room temperature I would say ,so I have no issues with the motor heating up it was the l350 that was hot.



B,
 
Mr.20c said:
I am thinking of just omitting the filter. Can't I coat the windings On the motor and avoid this filter alltogether? I was looking at this product, http://www.glyptal.com/Glyptal_Product_Data_Sheets.htm what do you think?

I am trying to get a grasp on what happens to the motors windings when spiked , are they moving, do they have a potential to rub against one another causing a short, why is it that inverter duty motors don't have the risk in damage as I am having with this motor, is it the winding size, coating,...etc...etc...:thinking:
B,
Click to expand...

You could coat the windings, for sure, but you'd need to vacuum impregnate them to get the varnish to properly penetrate the windings, and you'd still not end up with insulation equivalent to a modern VFD-rated motor :(

Basically what happens to older motors is that the high voltage spikes are enough to arc though the insulation, resulting in shorted turns and eventually a burnt out motor - not pleasant if it's a rarity!

The line filter (of the correct all-inductor type) slows down the rate of voltage change (the leading edge of the waveform) applied to the motor and reduces the chance of insulation breakdown - if you can wrangle a KA filter, fit it!

Dave H.
 
Thanks Dave,
I just got off the phone with my rep from Precision Zone and they are going to credit what i paid for it ($50.00) toward the V1000 drive (which is for the Oliver 88D-and that's going to need one as well......:(

So where would you recommend I go to get one of the KA filters. I talked with Jason from Precision Zone, they don't sell them.....

What really erks me is that he did not know about the filter, so I feel he just threw it at me without knowing what type.....As far as VFD's go- he is incredibly knowledgeable and have been very happy with him.

any thoughts?


Thank you,

B,
 
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