Anotherpower.com Forum
Renewable Energy Questions/Discussion => Renewable Energy Q&A => Topic started by: lighthunter on April 17, 2022, 08:50:06 am
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Hi all! Ive had a couple issues lately to do with enamel wire limits and since i enjoy the scenery at the edge it would be nice to know where it is.
Fuse blew last week on my 48v inverter. One leg of split 240 during backcharging at 4-5kw. Has been there for a couple years no problems. Fuse was not blown in middle but melted solder from end. Replaced fuse all good. Days later i grabbed an ir temp meter and checked surface temp of toroid during 4kw of back charging (usage never goes that high). The surface temp of toroid was 180°F or 82C the fuses sit in fan air stream just beyond the toroid. Perhaps bad place for fuses or maybe need to set fan control to run fan more as it only comes on to cool FETS.
Also working with a 150HP air compressor which motor tag states 150HP at 460V 3~.
The manufacturer of course set up locked inverter settings to output 400V3~max. Lord knows what actual hp rating was/is. When you drop motor voltage down slippage increases and V decline is not HP linear. This is TEFC. It used to work but cooked grease from bearings often. Motor failed once under warranty, twice since. Recently rewound motor and now monitor winding temp. It hits the 195°F 90°C mark at about 70% capacity. Ive requested access to parameters to scale up voltage but so far theyve not budged. I went to Danfoss the drive mfr and they can give me software to correct no problem but i will loose the IO programming to go that route.
I have asked the guy who rewound what is safe temp but he had nothing to offer, i will inquire again to get specs of wire he used.
Unless i do something crazy like fool the inverter buss volt feedback im out of ideas. How high can i safely go with surface temp of motor winding? Also, anyone know how to calculate HP at a lower than design motor voltage?
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HI LH , the motor should have no trouble running at 90 degrees C.
The problem with dropping the voltage from 460volts to 400 is that the current drawn will increase heaps for the same hp rating.
here is a link to some information on motor temperature ratings.
https://myelectrical.com/notes/entryid/122/understanding-electric-motor-insulation-temperature.
I would start by checking the motor current rating against what it is actually drawing under load.
Pete
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LH, a bit more information.
If the winding of the motor is B class then it will have insulation that used to be called elephant hide. It is a blue insulation with mylar on one side. The insulation between the winding phases is usually then a varnished fibreglass cloth.
If it is E or F class it will probably be Nomex slot insuation ( stiff white looking paper stuff). The insulation between phases will be either terylene ( E class) or Nomex for F class.
Of course it is difficult to measure the temperature of the windings when the motor is running, unless thermistors are embedded in the windings. Some motors have them but not many.
As far as the toroid goes that sounds pretty hot but then you are running a lot of power through it.
I have button type thermostats in my inverter that are 40degree C set point.
I hear the fan come on sometimes when I am using loads over a long time but it goes off pretty fast.
Maybe you could put some more vents in the inverter case to get the heat out faster.
you must have some serious battery banks to take 4 to 5 kw back charging.
I just picked up some new panels that came with an SMA 2kw GTI inverter. I am thinking of connecting it up as a mini grid but obviously need to have a voltage sensitive relay on the batteries to prevent overcharging.
So far I have never seen my batteries take more than 2kw in. My panels are way over sized here to take into account the cloudy , misty mountain weather.
Hope you get the compressor sorted
pete
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Hi Pete, I really appreciate the input, great info there.
"I would start by checking the motor current rating against what it is actually drawing under load"
This was my first clue something wasnt right, the nameplate current was FLA 166 460V 60hz, 110kw, SFA190, 94.5effic,, 680KG, Frame TEFC, SF1.15, PF .88.
Rpm 3585
What i saw was the amperage at 400v climbed to 160A at full load. The catch though is i remember the guy saying that he used smaller wire for some reason on the rebuild. So who knows what it can handle. Nameplate data is questionable. Upon install i squeezed a temp sensor under some windings i could reach through the box. I ran it for 40 hours initially at full load and it survived but had 0°C cooling air of a couple thousand CFM. Im sure it would not survive now.
Admittedly im being cautious but its obvious its days would be numbered if i just increased temp setting to 250F and pushed the start button and walked away. I dont need 100% capacity so id be ok with 70% but i need to get the voltage up somehow or it cant even do that. I could boost the 80V with 3 toroids with 200A 80V secondaries. Ive in fact had to do this in the past to level shift voltage and it worked well still in use to my knowledge. but doing this would cause current on the ground wire (common for the Y feeder) and i think the distribution has GFCI so that would cause a fault. I may have to get the software from the vfd mfr and somehow configure the pressure control loop another way. I just hate to alter an oem machine but when they violate such basic things as rated voltage on a motor... The motor failure under warranty proves it was a bad idea. Its possible they will still come through with the codes to change it but im not counting on it.
I just had a crazy thought, maybe nameplate volts is for wye and mfr. Is using as delta, that would explain?? Nope, just looked, nameplate says 460 with triangle which means delta which is how we are connected.
No blue color on windings. I will try to find out.
What do you think the temperature difference between core and surface of windings is? Thermal transfer of copper is good but the varnish has to slow that down some.
How can i go about calculating heat generated in the motor? For example if i know volts, amps, rpm and frequency, i can calculate slippage at a known input power. This might give me an idea of the red zone of loading. Im guessing all motors exhibit a normal range of slip and anything beyond a certain point results in an overheat motor.
Looks like ive only got two options, reduce load, or increase voltage. I guess replacing motor or scrapping compressor might be options as well but would not make those happy who've just spent $14k on it.
On my inverter, I think the toroid is ok with the temp, it just as pretty as the day i finished winding it. There is a monster 243 cfm fan that I will set to run more often though. Maybe having the fuses in the hot air stream is a good backstop for temp limits due to an improper fan setting ::)
" SMA 2kw GTI inverter. I am thinking of connecting it up as a mini grid but obviously need to have a voltage sensitive relay on the batteries to prevent overcharging."
Hook it up, you wont ever regret that. They are so efficient you would be amazed. I had a group of 12 panels direct connected through relays, 29 volt panels two in series, 6 sets in parallel. Never got even close to 2kw. Connected in series, on a grid tie, I saw those same panels run near 3kw whenever sun is shining. I think they are 240W panels. I will admit my wiring was not perfect but it was night and day difference in power. You can control output in a number of ways. I use high volt relays just on/off with 30 min time delay but a common relay can be used with a dump resistor to parallel across the dc inputs and cut output in half. Or a relay on AC side with a 1 to 2 kw water heater element. You can never have too much power:)
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Does the 3585 nameplate rpm say 15rpm slip at 460V 150HP 166A??? I never thought about it before. Thanks again for your thoughts!
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Hi LH, I am used to using 50 hz here so a 2 pole motor would have a synchronous speed of 3000 rpm.
In your case it would have a synchronous speed of 3600 rpm. There has to be some slip in an induction motor to produce torque so yep 3585 would be about right.
Most motors I worked on had about 50 rpm slippage. So a 2 pole motor would run about 2950 on 50 hz, a 4 pole motor 1450rpm.
Formula is N ( speed) = 120 x Frequency/Poles.
If you are using a variable frequency drive and slowing the motor down it will not cool as well as it should.
What revolutions is it running at when on 400 volts?
It may be worth adding an external fan to increase cooling if it is running too hot.
The only reason I can think that the motor winder would put thinner wire in is if he did not have the guage he needed on hand.
Big motors like that have many wires in parallel. Usually one measures the guage of each wire, calculates how many circular mils that adds up to and replaces it with the same area of wire. Different guages can be used in parallel as long as the area of the winding is the same.
Some motors ( Siemens) is one example are very tight to rewind. They pack a massive amount of wire into the slots are are a mongrel to rewind.
Pete
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Hi Pete :)
Ive not made much progress as yet but am hopeful the mfr. of compressor will come through soon. I emailed them about coming onsite to make the voltage change hoping they will go for that rather than giving out access to their software.
What revolutions is it running at when on 400 volts?"
At 400V 60Hz is the output frequency, as for the RPM , i dont know yet. I will try with a tach to get that number. Hopefully i can estimate load or how underpowered it is by the slip.
"may be worth adding an external fan to increase cooling"
I wish i could... fact is i dont think i could improve on it. It uses the entire enclosure for the aftercooler radiator airflow which is ducted from outside and has a centrifugal fan of something like 10HP. There is so much air flowing around that motor its crazy, i dont think i could improve on that. It literally takes effort to shut a cabinet door while on there is so much air pressure from fan.
"Siemens" you nailed it, thats the brand of this motor.
I will get an rpm measurement at various frequencies including A and V.
Thank You so much for your thoughts! I hate to give up on it seems so close. My hope is that if voltage were bumped from 400 to 480 the motor would not run high temp.
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Hi LH.
Siemens motors eh, the bane of my motor rewinding days. Most other motors have plenty of spare room in the slots where the windings go. So some more room for cooling, not Siemens, they fill the slots totally.
They also seem to have small frames for the HP ratings they squeeze in.VFDs create. There is mention of sparking and heating in the motor bearings and the need for insulated bearings in some cases. Sounds like it may relate to your compressor.
Also compressors being required to start under load can be a problem, if the drive is set at too low a speed or voltage the motor will not have the torque to overcome the load and will run hot.
I wonder, I helped a fellow sparky once who was having trouble with a motor on a VFD that was drawing way over the rated current. It was only a small motor but it was connected wrongly. The motor was only 1kw from memory and it was delta connected. When the drive was turned on it ran very hot, the current was way up and the VFD just shut down.
I suggested that we change the terminal connections to Star and that solved the problem.
Seems that someone changed the motor or changed the connections and it all went pear shaped from there.
Check the nameplate on the motor to make sure it is not supposed to be Star connected, that would explain the max 400 volts on the VFD. Long shot but worth a check.
Pete
Have a look at this article, it is short but mentions some of the problems
https://new.abb.com/drives/segments/motors-and-drives-in-potentially-explosive-atmospheres/effects-of-variable-speed-drives-to-motors
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Star connected, that would explain the max 400 volts on the VFD. Long shot but worth a check.
For a given motor, I'd expect that a delta-connected motor would run on a lower voltage than the same motor star-connected.
But they're not so close as 400/480V.
I think a 480V 3phase supply would only see 277V across each coil in a star connected motor.
Isn't 400V common in Europe? Is it possible the motor and VFD were not a "pair"?
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HI Ross, I was mainly thinking of the current the motor is drawing. For it to be running so hot and to have burnt out twice already something is definitely wrong. In Star the motor would only be drawing 1.73 times less current. Whether it would have the power needed for the compressor is something that would only be found out on experimentation.
You may be right the controller may be the wrong one for that motor.
I guess the manufacturer needs to come and look.
Pete
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Pete, youve already been way more help than the mfr reps. Seems like youre onto something. Wierd thing is, I never got to remove...disconnect this motor, others did and I was really scratching to understand how to hook it up. I do know there are 6 leads, always were and 3 terminals, (two each and not 1 each, with 3 bound together.) Since this is VFD the wye/delta start is not needed. Im willing to listen to your experience on this cuz ive tried all i know and it works well, just generates too much heat. Makes total sense downsizing wire if he couldnt get wire in slot.
Ross, your right also, i'm guessing where this came from, chicago pneumatic, 400v might have been the likely voltage fed to vfd so wouldnt have been any more available. I did talk with rep of mfr. Of drive, danfoss, and he said it was capable of outputting 480 no problem but then encountered the locked software. Soon i should know if they will send a guy out to change it. If not, im tempted to reload danfoss software, my hesitancy on that involves liabilities of a blown compressor. Even though i know zero chance of a voltage change causing that its just the idea of a modification. Changing a volt setting in my opinion is not changing functional design. Reloading software deleting I/O and rewiring/configuring the pressure control loop is changing design. At the time of failure a new motor did not exist even though this unit is little more than 10 yrs old. Now i really wish id have insisted on a "new motor". Yet this issue existed when it was delivered new. What Pete describes with need for insulated bearings etc fits this description exactly. Any thoughts if bearing arcing is a function of heat or not related? Ive heard of this before, even seen it but ive never understood it. Is it always a VFD that causes it? Or is it motor design? Maybe we could remove the vfd, put wye/delta contactors for startup and run it direct. Ha, here i go again wanting to change design. I better stop thinking about this :)
Thanks a million guys! Your input is appreciated!
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Hi LH , from what I have read the bearing sparking is caused by the spikes on the waveform fed from the VFD.
I am guessing that the sharp peaks are inducing a voltage into the rotor shaft and the only place to earth is through the bearings.
The shaft must be operating as one turn of a transformer and as such generating a current flow through the bearings.
I may be wrong but then it makes sense to me.
With a sinewave the drop off of the waveform is much more uniform so an induced voltage would be lower and less damaging to bearings.
It doesn't make much sense to me to have a VFD on a compressor. Maybe they are trying to limit starting current under load by using the VFD on startup but a Star/Delta starter or a compensator ( transformer) starter would be much simpler.
LH on the motor leads, it is very important that they are connected the right way.
If a phase were reversed then problems will happen fast.
Hopefully the leads are marked so that no one can stuff up and get the starts and finishes mixed up.
Usually European motors are marked U, V , W for the start of each winding
and U1, V1, W1 for the ends.
So delta is U and V1 connected together
V and W1 connected together
W and U1 connected together.
Star would be
Line connected to U, V, W
U1, V1, W1 connected together.
I am not sure what you mean by the terminals when you say two each and not 1 each it sounds like the leads are in parallel. Often if the lead cables are too big one would parallel them up. But then you say that 3 are bound together, that sounds like a Star point.
Can you put a photo of the terminal block and leads up.
Pete
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Hi LH , I have attached some information on terminal markings of motors and connections.
Some of them are complicated as they are for Dual voltage, or dual speed motors.
It may come in handy though in the future
good luck
pete
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Thanks Pete! Looks like some valuable info to hang on to.
This is how i hooked it up.
(1,6)--(2,4)--(3,5) doesnt the nameplate info say the 460V is for delta connection? Or am i reading that wrong?
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Hi LH, looks right. The nameplate does say 460 volt for delta.
Your connection looks right for Delta.
With Delta connection each phase winding has 460 volts across it.
Talk to the manufacturers and see what they say about trying it in Star.
In a Star connection you would have with the 400 volts your controller can supply a phase voltage of 230 volts.
The current would be down too so you may not get enough power but at least it would not run as hot.
See what they say, as it seems the VFD is not suited to the motor running in Delta.
good luck
Pete
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Hi LH , I came across this explanation that may help.
As the frequency of the drive is reduced the voltage has to be reduced also.
So in your case your motor is rated at 460 volts at 60 hz.
That is a ratio of 7.666.
if the voltage is reduced to 400 as in your case then the frequency needs to be reduced too. that would mean the drive should be putting out 52 HZ.
The motor would then be running at 120 x 52/2 which equals 3120 RPM.
If possible back the VFD frequency back of to 52 hz and keep the voltage at 400 and see if it runs cooler and has the power and torque needed to run the compressor.
Pete
AC motor characteristics require the applied voltage to be proportionally adjusted by the VFD whenever the frequency is changed. E.g., if a motor is designed to operate at 460 Volts at 60 Hz, the applied voltage must be reduced to 230 Volts when the frequency is reduced to 30 Hz. Thus the ratio of volts per hertz must be regulated to a constant value (460/60 = 7.67 in this case). The most common method used for adjusting the motor voltage is called pulse width modulation (PWM). With PWM voltage control, the inverter switches are used to divide the simulated sine-wave output waveform into a series of narrow voltage pulses and modulate the width of the pulses.
With a standard AC across-the-line motor starter, line voltage and frequency are applied to the motor and the speed is solely dependent on the number of motor stator poles. In comparison, a VFD delivers a varying voltage and frequency to the motor, which determines its speed. The higher the frequency sup plied to the motor, the faster it will run. Power applied to the motor through the VFD can make the motor working speed lower than the nameplate base speed, or increase the speed to synchronous speed and higher. Motor manufacturers list the maximum speed at which their motors can safely be worked.
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Hi Pete! This is great information! Reminds me of a time years ago when i had a pump failure on a laser and no replacement, i found an R.O. pump and plumbed it in but it didnt have enough flow. I put an AB vfd on it and turned the freq up and it worked, i want to say 76hz it ran very warm but got us through till oem part came. In this case we'd do the opposite. I have already tried reducing max output to 70% which helped but still overheated. I'm guessing by what your saying, the scaling needs to be adjusted. So that we hit 400v at 52hz instead of 60hz. Some drives have an autotune for this.
Trying to wrap my head around all this... if switching connection to wye works that would mean the 400v is too high for 100% duty cycle in delta, (magnetics are saturated causing excess current wasting energy in heat?) If reducing freq and maintaining 400v in delta works, then magnetics were too weak and allow too much slip for load applied causing excess heat?
So there are at least two maybe 3 possibilities to improve this situation without a motor change. Thats good news!
So far the reps from CP have not been people who know anything about motors or vfds, its been more like... "let me talk to someone and get back to you" I look forward to trying this information and getting rpm vs freq information for before and after.
Thanks and have a great day!
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Hi LH, hopefully lowering the frequency will sort it out. Of course it will run slower but hopefully not so hot.
My understanding is that the frequency needs to be lowered when the voltage is lowered otherwise the motor will draw more current as the frequency falls.
Inductive Reactance XL =2 x pi x F x L
So pi doesn't change 3.14 is a constant
F is the frequency so if it is lowered then
L inductance stays the same but
XL inductive reactance will fall, which means that the motor will draw more current, hence dropping the voltage compensates for the lower inductive reactance.
I have not had a real lot to do with VFDs over the years, I did my apprentiship as a motor rewinder. VFDs were not very common then.
Good luck
Pete
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HI LH just wondering if you have had any luck with the compressor.
Did you manage to drop the frequency to test the current draw and heat at 52hz,
anyway just wondering if you had any luck
Pete
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Hi guys! :)
We've had a myriad of other breakdowns to attend too lately. The guy from tech support finally responded to the question this week (attached) and we got some time yesterday to try a couple things.
So the first thing was i brought in a phototach i had at home, the control max speed was set to 75% so max rpm for test was 45.75hz, the measured phototach rpm was 2733 rpm and 175A 400V as read on vfd display. Vfd display also read 2725 rpm.
Nameplate rpm calculation is 60hz=3585rpm so 45.75 hz = 76.25% * 3585=2733.56.
When i saw that my head went blank because i was so sure we were underpowering the magnetics of this motor causing slippage thus the thought to raise voltage to cure problem, in fact, if no other solutions were obtainable, i had in mind to install an orfice on intake and run it at a vacuum to reduce load. When i saw this, all those ideas vaporized.
So, it appears the reason motor temp climbs too much is because we are magnetically saturated and pushing current that isnt necessary to spin the mechanical load... (screw). Correct me if im wrong but if anything, we need to reduce voltage correct??
So Pete must be right about the wye choice, we looked on net and seemed like a 30% change by switching connection to a wye. We did so and fired it up. As it spun up, the current meter on vfd seemed to be wildly hunting to 170s then down and up. Not being able to hear with tons of other noise we hit the kill switch. We envisioned a situation where the vfd freq climb did not match the acceleration of the shaft under load which could cause a bad event. As yet its still connected as wye but locked out.
I plan to switch it back to delta next and verify nothing is hurt which i dont think it is.
So are we right in thinking the delta performance is real close just maybe a bit oversaturated? After all it ran for 120hrs. with subzero F° cooling. Maybe im just wierd for thinking winding temp should stay below 100C? Shouldnt there be more slippage than that?
I feel like if tech support werent so absent all this needs is a vfd tune which is a standard procedure for all large HP vfd setup...
I get their argument about motor should be identical to original and you wont have issue, still vfd tune is always done with new motor install regardless if oem or not.
I think the wye connection would be fine also with new vfd settings. Part of me wants to call Danfoss and get original software reload for vfd and do the normal setup an this would likely be running. Then im faced with wiring my own pressure control loop which im not crazy about modifying an oem machine...liabilities.
Sorry if i sound confused, Ha! I am.
(I meant to include what i wrote to tech support but it wasnt in photo i will try to add, it said something like. We need this machine running and if you wont give us lock codes, can you send a technician on site to make corrections? That was his response.)
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LH slippage is not your problem there.
Synchronous speed = 120 x Frequency divided by number of poles.
So 120 x 45.75 divided by 2 = 2700 rpm.
As the frequency is reduced the voltage must also be reduced, otherwise the motor will draw too much current.
As the frequency is reduced so it the inductive reactance. Reducing the voltage then keeps the maximum current within specs.
If the motor is designed to run on 480 volts at 60 hz
then at
45.75 hz it needs to have a supply voltage of 366 volts.
Looks like in Star the motor was not getting enough voltage to run at full power under load.
In Star 400 volts line voltage would mean each phase only had 230 volts. Not enough at that frequency.
Put it back in Delta and drop the supply voltage to 366 volts at the VFD.
Pete
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Hi Pete! I agree, I wish i could. The VFD is locked as far as changing anything. I can select one of about 6 programs but they are for different specific machines including I/O differences.
The voltage reading above was not a new reading and i need to check it since it was from the 60hz value. The other numbers were read at the time of test.
Am i right in thinking if no slip is present, the volts are high enough? Perhaps higher than needed?
Thanks for your comments Pete!
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HI LH, if there is no slip in a squirrel cage motor then it would have hardly any torque.
There needs to be some slippage so that the lagging magnetic field creates torque.
Unless your gear is Laboratory standard there will be some errors in the readings you get.
Like I said the voltage has to fall as the frequency goes down or current will rise and the motor will run hot.
It is hard to figure that whoever built the machine did not set it up correctly in the first place with a decent program in the VFD that varied the voltage to suit the speed of the motor.
It may have been a rush job
good luck
Pete
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Hey Pete, yes this inverter is programmed to ramp voltage with freq/rpm. From memory, ive seen it down to 120v/phase at the minimum freq. around 700rpm.
We had chaos on thurs and no work on friday due to a computer network outage. I will get the voltage reading at 45.75hz on monday.
Since the slippage is (normal) and current is high, This much points to volts being too high at that particular frequency? Am I understanding right here? Assuming all other aspects of the motor and load are correct of course.
My reasoning for doing the rpm/slippage test was to determine if for some unknown reason the shaft was loaded too much or volts were too low, i thought there would be more slippage. Maybe my equipment was not accurate enough to draw that conclusion.
I cant thank you enough for your input on this. Ive just never really had to mess with induction motor behavior before. The only other time it got close to this was a new fan/filter unit kept tripping 20A 480v breaker like once a week. (I dont install this stuff, just try to fix it) so this went on, company was crap to zero support
from italy i believe. Then burned up disconnect switch and breaker. I got those replaced under warranty. Motor then burned weeks later. I had it rewound because they couldnt supply new one quick enough. I called. the motor rewind guy and gave him measurements and he said its gonna fail again if you leave it that way, so i ordered a new motor next size up thinking this would cure problem now the electrical supply was too small to handle it so put a vfd on it and dialed it to 50 hz and its been about 8 years since weve had trouble with it. Im pretty sure the company fitted the wrong centrifugal fan blade in it causing the grief.
You dont usually question the design of this stuff but this was a clear example where they got it wrong. Because the motor on this compressor failed under warranty and twice since leaving all things OEM i think that proves thats the case here as well. They never bothered to put a temp sensor on motor. I could just remove it and push the button and walk away, let it cook. Who knows it might last another two years. Ha!
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Hi LH, one other thing to check if the motor is ever apart again is the Rotor.
Squirrel cage rotors do fail.
The bars in the slots usually break at the rings that connect them together at the ends.
This causes the motor to hunt and make strange noises, they sound like they are trying to get up to speed but can't quite make it so they emit a strange humming noise as they run.
I once walked into an autoelectric shop I worked at a few years earlier. They had a 100hp motor that they could not find anything wrong with, They were just about to start chopping the stator windings out when I looked at the rotor.
The rotor had copper bars that were silver soldered to a brass ring. Sure enough some of the bars were broken.
I managed to stop the fellow with the air chisel just in time. He was just about to start chopping the stator winding up.
You could always slip some thermistors into the windings if you wanted.
Unfortunately as the controller is setup, the motor will probably just keep tripping the thermistor relays anyway.
Good luck
Pete
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Update:
Thanks again Pete for all the ideas and thoughts on this one. All attempts to adjust the volt/amp curve via vfd programming failed as the OEM disallows it. Weve yet to get any real support from those people.
The compressor has been running fine for a while now. I drilled a hole near the bottom of the end frame and put compressed air to it so it blows cool air through the cage out the cover of electrical box. A co-worker drilled the fitting a bit larger as the cooling requirement was higher than i had anticipated. It takes around a 6hp efficiency hit just to cool it but it works. Runs about 175F now. Whats difficult for me is knowing exactly whats ok? A different unit had oiltemp that reached 221F today. Pressure washed cotton fuzz from radiator and now at 196 where thermostat regulates it. Maybe its fine for winding temp to be 250F no one i know will go there and articles written about it tiptoe around the subject. Oddly most manufacturers do not put temp sensors in windings yet a common house fan includes this as a safety device. A thermal cutoff or tco. As i write this im reminded of an event years ago... 1998... how time has gone... when a laser roots blower also siemens motor, failed due to a temp sensor in winding. I jumpered and machine ran, i ordered a temp switch in a T0220 package and inserted/epoxyed into winding at end of motor seems like i started at 110C and kept having to order higher ones till i got one that didnt trip under normal circumstances. Seems like the number was 115 or 120C when i finished and that one ran for years that way. So by that info i can set this at 250F and reduce the orfice size to maybe 4HP of cooling. Of course an air booster in reverse trading pressure to volume would reduce the flow requirement again. Anyone else agree i can increase thermal trip point to 250F or 120C?
I kinda feel stupid i forgot the eqperience i learned back then about winding temp.
Perhaps i better ask the elder gentleman what class wind wire he used for this one.
Its not an ideal solution but it is a solution and it does run welll now. Anyone have an idea on a moisture sensor for air line. I will need it to fault on humidity as moisture will kill windings too. So far our dryer is flawless but theres no feedback to stop anything if it doesnt remove all moisture.
Hope everyone is doing well, i havent had much time to post as garden, work and other odd jobs have been over the top lately.
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Hi Lh, well that was a novel solution.
Here is a link to a page about winding insulation temperature ratings.
A H class winding will have White Nomex slot insulation. The rest of the insulation will be mica or fibreglass for phase insulation and leads.
Pity that Siemens pack the motors windings in too tight and fit too big a motor into a small frame.
Gone are the days where open frame motors could be run at double their ratings. Nowadays the ratings are absolute max.
I hope you are well and that the workaround stays working.
I guess some sort of air dryer like spray painting sets have could work but sounds like you are putting a lot of air into the motor.
Cheers
pete
https://www.hecoinc.com/blog/electric-motor-insulation-class-what-is-it
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Hey Pete, that Heco document is wonderful. We still have no email service where i work so have not gotten info on winding class yet. Because the alarm temp control i put in only has a max setting of like 209F thats what i set it to. It runs at about 185°F so am real happy with it now. The motor current at 60 hz 3600ish rpm is 200A, nameplate is 166A, thats a bit concerning but it doesnt have to run there very often.
Again that heco document is better than any i had found on the subject.
The heat here is crazy lately like near 100 with high humidity but it rained last night so its been nice today. Crops are doin great. Its hard to make it through June without your garden being wiped out by drifting farm chemicals but this year is a bit better, lost some peppers but the rest pulled through. Even the apple trees have leaves still looking like a leaf rather than the gnarled curled shape they usually get from sprays. Ha for years i thought it was cedar apple rust until i finally caught on to it. Hope everyone is doing well!
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Crops are doin great
Hah, you're lucky.
Where I am, the *WEEDS* are doin' great. Other things ok, but weeds are going bonkers!
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Spray drift eh. I was talking to a beekeeper years back and he was totally confused because he lost something like 100 hives and could not work out what caused it.
I asked him where they were and if there were any tree plantations nearby. He told me and I knew his problem straight away.
Spray drift from the plantations was it.
The plantations were sprayed regularly with a chemical called Alphacypermethrin. It is used to kill the eucalypt beetles that eat the trees.
Well as we know if it kills one insect it kills them all and the bees were not far from the plantations.
I had a friend who had his whole crop of Flowers that he had been selectively breeding for 20 years wiped out by the farmer next door spraying 2-4-D.
The farmer denied it but also happens to run a dairy and has a well frequented cheese factory. Unfortunately for my friend and his 20 year Hellebore program the farmer was from a rich family with political connections and nothing was done about the spray drift.
Our state claims to be a Clean Green state, but nowhere is safe from chemical sprays.
Glad the documents are helping and hope the problem with the motor stays fixed
Pete
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Spray drift
nowhere is safe from chemical sprays.
It can be a real problem.
I'm on a modest 22 acres. We moved here 20 years back and one of our conscious decisions has been to use mechanical and biological weed control measures - we cut and dig out blackberry roots and all, we encourage the Chrysolina beetle to control St John’s wort, slash and leave Pattersons Curse, and over-graze some areas where the sheep and alpacas can control nuisance weeds.
The amount of bird life here has increased by an order of magnitude both in diversity and quantity, we have heaps of frogs and lizards and other critters that were virtually absent when we got here, and lots of sensitive native flora like various insectivorous plants, kangaroo grasses etc are re-establishing.
We have neighbours who still choose to spray poisons around, and the council, but all are well aware of our concerns and "organic" status and most do actually make a decent effort to ensure we get no spray drift.
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Hi all! The compressor has been behaving well with winding temps that peak around 190F 88C, i cant say it works constantly flat out at 3590rpm but it does what needs to be done.
Another question about windings, hopefully an easier one :) HA, Im planning to make a large boost converter. If i use a laminated core from a toroid power transformer as an inductor, how high can i go with frequency? Or is that totally not a good idea? Ive some E55 ferrites i could use too but im looking to get a couple kw with an 8 to 1 ratio so id likely need to parallel a few. An 8 to 1 is tough to achieve anyway and i may need to series two windings on the same core to get the lift i need at that power level so the donut just gives lots more room to do it. Thanks in advance for any ideas.
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Hey Pete! Am beefing this up for a friend. How many 14awg in hand for 100A, seems like 5 is right number but if i remember pj formers had more than 5 i dont wanna go too short. The original is a 2kw 120/240 and i need to lay on the low v primary and another 120 to stiffen it a bit more and make it true split phase. It should make 5kw continuous if i do it right. Yep it will b an 8010 inverter Hope you and everyone is doing well.
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Ha! I was way off. Looks like i need 17 in hand, 23 turns = 391 total for primary, the 120v will need 2 in hand x97 turns=194 total for 120v. Thats a total of 585 additional turns. Wonder if theres a formula for hole size required?? Seems like that will be hard to do with a 63.5mm hole. Cross section of 14awg is 2.08mm so 585x2.08 is 1217 sq mm 63.5mm circle is 3167sqmm so it should fit. The thing is already very heavy.😁