asynchronous motor dimensioning with sine load

[Taipan95]

Good morning.
I am trying to improve my knowledge about the drives electric motor + reducer (+ inverter, in this case).
I would like to try to dimensional a three-phase asynchronous motor, to be adjusted with inverter, trying to "copy" a case study that I saw at a training course but where it starts with the system already dimensioned and then focus on other aspects (in specific, on reaction forces on the bearings of the handle).

the system is a biella handle, with the biella that is connected to a fixed load of 20kg.
the crank must take to speed of regime (300rpm) after 2.5s, with a ramp to pleasure (I was considering a linear ramp from 0s to 2.5s for simplicity).
the crank is 175mm, the biella is 519mm.
We admit that these are all the starting data.

I tell you for completeness that in the case study is also inserted a motor between the crankshaft and the asynchronous motor, with a ratio about 3. But I guess that's coming later.

to be able to choose the three-phase asynchronous engine, I guess I have to calculate the torque profile needed to move this system with the desired timing and speeds. this should at least give me an order of magnitude on the size of the engine to use. After that, I think, they should follow the considerations on the inverter and the reducer.

the problem is that in this case I have a sinusoidal load, because the mass from 20kg will move of alternating motion vertically following the bike of the biella-manovella.

I tried to calculate the necessary torque profile at 300 rpm, for a spin of crank, and I attach it together with a box showing the system. However I do not think it is correct, because it does not take into account the presence of the inverter and is also done only for the speed of regime without considering the transitory.

I don't really know where to start, I'd like someone, with a little patience, to be able to lead me to figure out how to size everything... I managed to find the engine catalogs and gearbox used in the case study, I also attach those.

the chosen engine is: m90sa4
the chosen reducer is: 411a one step 38nm

thanks to anyone who wants to contribute

 

[meccanicamg]

then if the gear motor turns at constant speed, after coming to regime is one thing. if the gear motor has to continue to accelerate/choice is another.
the reducer is placed to get a motor that works at 4 poles then around 1400rpm where best expresses power/pair.
If you look at similar discussions we have already talked about it.
the acceleration you can give is given, fixed motor, from the force of the load and from the inertia to accelerate in the transitory.
I recommend you to use the appropriate programs of motor builders as it can be siemens sizer, where you make a new mechanism, or describe the features, choose the type of drive, motor and gearbox and then if you use different brands look for something similar.alternatively there is rockell motion analyzer that also interfaces with solidworks...but I prefer siemens.
the inverter must provide the nominal torque in s1 and if you use the transient s3/s6 must be able to give you overcurrent. otherwise....put a bigger drive.
If you want a controlled thing, at least the encoder in the engine.
by hand it is not worth losing time especially if you are doing something bitten at work.
then if you want to do the theory and calculations by hand you can also do at least partially to check.

 

[meccanicamg]

other thing I recommend you to do is use serious motor manufacturers brands, where they have a complete catalog of all information as well as having the ability to configure and download 3d models.
red reducers is done well, otherwise there is bonfiglioli even if the configurator is not the best. there is sew that is done well even if a little more complicated on the thousand options.

You need to know force that is transmitted to the crank, degree by degree and on that then work on accelerations, if you want to make the account by hand.

I attach the pdf, if there was no web resource in the day.

 

[Taipan95]

Thank you for the answer,
But let's not know that you want to use a 4 pole and that you want to put that mororiducer x... we are literally blank, and there are no software.

how should you set paper/penna/excel calculation? I guess I need to be able to get the performance, even indicative, of the required couple... Otherwise the engine I don't know exactly how to choose.

Surely the software is comfortable, but I don't want to be dependent on a program... or anyway I would like to understand that equations use to pull out the results.

we hypothesize that the inertias of biella and crank are negligible, so to have only the mass m from 20kg to move up and down.

being a system without encoder, I already know that the instant real speed will never be like the profile I wanted (linear climb up to 2.5s and 300rpm, from there constant...). But this is assumable as the average speed trend, instantly it will oscillate around this value but I don't know just how to set the equations to get it

 

[meccanicamg]

normally if you use a three-phase asynchronous you always take if possible a 4 pole because the best energy condition of a three-phase motor is turn to 4 poles. all others spend more current than surrender.
if then to turn to 1400rpm you should need an overly low or high-vabbeh reducer ratio....you sacrifice the 4poli and you travel to 2 or 6 poles.

That always.

for hand/excel calculation you must first calculate with the pdf of the post before the force transferred from the plunger to the rotary crankshaft, parameterized with alpha.
then by imposing the linear acceleration you will have the law of acceleration to the biella manovella and then backward you have the variation of acceleration to the rotating shaft.
inertias and pairs to win multiplied by angular acceleration get the pair.... buy with gearbox and motor and if you are in the curve ok, otherwise change engine. Iterative.

 

[iron_mec]

normally if you use a three-phase asynchronous you always take if possible a 4 pole because the best energy condition of a three-phase motor is turn to 4 poles. all others spend more current than surrender.
if then to turn to 1400rpm you should need an overly low or high-vabbeh reducer ratio....you sacrifice the 4poli and you travel to 2 or 6 poles.

That always.

for hand/excel calculation you must first calculate with the pdf of the post before the force transferred from the plunger to the rotary crankshaft, parameterized with alpha.
then by imposing the linear acceleration you will have the law of acceleration to the biella manovella and then backward you have the variation of acceleration to the rotating shaft.
inertias and pairs to win multiplied by angular acceleration get the pair.... buy with gearbox and motor and if you are in the curve ok, otherwise change engine. Iterative.

Hello mechanicsmg... reading the discussion I was interested in understanding if you could kindly explain when electric motors can be designed instead of selecting them commercially from some catalog of some company that provides them, and explain also in detail when it is convenient to design or choose them from business, in both cases, always if it is possible to calculate and dimensional their stator and rotor diameters, according to the current that serves, for a certain nominal power to make a machine work? . . .
Thank you so much if you could explain these two details, of course, if the electric motors can be dimensional, in this discussion. . I'd be curious enough to understand these two details.

 

[wert]

- Yeah. reading the discussion I was interested in understanding if you could kindly explain when electric motors can be designed instead of selecting them commercially from some catalog of some company that provides them, and explain also in detail when it is convenient to design or choose them from business, in both cases, always if it is possible to calculate and dimensional their stator and rotor diameters, according to the current that serves, for a certain nominal power to make a machine work? . . .
Thank you so much if you could explain these two details, of course, if the electric motors can be dimensional, in this discussion. . I'd be curious enough to understand these two details.

I speak as a mechanic and not as an electrotechnic... the asynchronous motors in ca can be customized but always within the limits of the size of the plates that make up the static package, which are standardized (50-63-80-90-100 etc.). Depending on the size you have available, you can realize tozzi engines (large diameter and small height) or snelli (small diameter and large length). then you can play on the winding of the stator; wire diameter and number of edges affect performance. in principle, with more copper there is, with more the engine is performing, finally there is also the possibility to change the trajectory (the space between stator and rotor). but for the choice of all these variables I have always entrusted myself to the advice of the supplier.

 

[iron_mec]

but is it better to customize them or choose them in the catalog?

 

[wert]

but is it better to customize them or choose them in the catalog?

I forgot to specify that I was referring to the sizing of engines for special uses, where the project envisages are used in particular products. you buy stator and rotor to your specific and you designer then you have to draw the case and flange bearings (or caps).
in this case you can request that the shaft end to be coupled with the other parts of the cinematic chain is executed in drawing (engineering, groove, tabs or special keystrokes).
and above all, it is productions of a certain series.
but if you don't have any of these needs, choose from catalog, abounding a little with power and you're fine.

 

[meccanicamg]

Hello mechanicsmg... reading the discussion I was interested in understanding if you could kindly explain when electric motors can be designed instead of selecting them commercially from some catalog of some company that provides them, and explain also in detail when it is convenient to design or choose them from business, in both cases, always if it is possible to calculate and dimensional their stator and rotor diameters, according to the current that serves, for a certain nominal power to make a machine work? . . .
Thank you so much if you could explain these two details, of course, if the electric motors can be dimensional, in this discussion. . I'd be curious enough to understand these two details.

Let's put it this way: the engines are chosen in the catalog with the possible variants of the manufacturer.
DIY customizations, that is what you say "build the engine" you do if you have to incorporate the rotor into a special machine.
I do not design engines on the construction side, I am a user.
My suppliers have catalogs and besides those they also have special wrappings built over the years to optimize performance....but they are in their beautiful rectangular box.
If I want to put the boxes on top, on the side, axial fan, radial turn....
but copper and magnetic sheet does not size it.

 

[iron_mec]

So then, the current engine is only designed for special machines, and not on custom-made machines as well as for gearboxes attached to it and any other mechanical component?

 

[infallibile_GF]

the mat (asynchronous motor three-phase) is a motor constructively and mechanically very, very simple, robust and reliable. they all look like, of all different manufacturers, in fact they have standardized sizes. also performance, performance, absorbed current, power factor, vary very little, at equal size, among the various brands. and in fact I do not understand the sense of designing from scratch a mat apart then that it would cost 100, or 200 times more than standard ones, which are extremely cheap. another aspect is that the mats, combined with an ivnerter, are rather flexible engines, being able to vary operating speed and torque. a motor size can cover a wide range of speeds/ operation pairs.
the only reason to design a custom mat is in case it is a giant motor, with power of several hundred kw, which therefore does not fall into the standard sizes, or that it is very small, microscopic and also in this case would not fall into the measures that are found on the market.

 

[Taipan95]

for hand/excel calculation you must first calculate with the pdf of the post before the force transferred from the plunger to the rotary crankshaft, parameterized with alpha.
then by imposing the linear acceleration you will have the law of acceleration to the biella manovella and then backward you have the variation of acceleration to the rotating shaft.
inertias and pairs to win multiplied by angular acceleration get the pair.... buy with gearbox and motor and if you are in the curve ok, otherwise change engine. Iterative.

I'm sorry, I keep not understanding what you're explaining to me.

I have a system that must take from 0 to 300rpm in 2s, and then go to constant speed. being an oscillating system, what I can control is the average speed profile (as mentioned also in pdf) and not the instant one that instead expects me to shine around it (photo allego).

How do I impose acceleration or speed profiles if I don't know them? I know only the average speed trend, but I don't know instantaneously during the oscillatory motion what are the values achieved by the system... Because I don't know what kind of engine I want to use... If I used a super-sized engine, I imagine that the synenoid would flatten more and more until it became like the black linear performance in the figure.

 

[infallibile_GF]

I believe that the engine does not follow that profile, I think it is set on a certain constant speed regardless of the power. also because there is also the inertia of the rotor itself of the motor that acts as a flywheel. if it is oversized the engine will have a higher speed, if it is less powerful it will have a slightly slower speed. if it is undersized the engine stops. I'm not an engineer.
I think your system looks like an alternative air compressor. with the electric motor acting on the piston that compresses the air.

 

[meccanicamg]

then we do so: impose on the translating mass an acceleration and obtained that of the rotating shaft of the biella/manovella.
if the acceleration to the tree multiplied by the inertias and the masses, correctly evaluated in order to get instant pairs point by point will stand no curve of the chosen engine, the system will be ok.
with this reverse process you will have a variation of acceleration of the engine according to the positions of the mass.
As I have already told you....I'm in a program and you're done throwing non-productive time.

 

[Taipan95]

then we do so: impose on the translating mass an acceleration and obtained that of the rotating shaft of the biella/manovella.

but the problem is exactly this for me... What acceleration do I have to impose if I don't know the progress? I don't know what type it can be, nor how much it could amount. . .

I quickly tried to cuff with the rockwell program, but I have some doubts about the results obtained... As soon as I can maybe put them so we discuss it.

the fact that the load curve must be "inside" that of the engine in s1 or s3 I understood it, the problem is that I can not determine the load curve or the values that the load instantly could assume... with rockwell software I got some results, but I want a confirmation from someone who understands more than me

 

[Esselle]

time ago, I compiled this excel that I train to try to dimensional a mechanism. see if it can help.

 

[Taipan95]

Hi.
thanks for the shared file... I had a similar one. the problem is that it does not consider a speed profile, but only instant speed. . .

 

[biz]

You set it up. based on that size your engine.

 

[meccanicamg]

If you want the load to accelerate linearly in 5 seconds from zero to 4 mm/s you have the motorcycle law. divide in n points and revenues the corresponding to the crank thus determines torque to the motor.
if you have a drive and an inverter you are the one who controls. If you have an asynchronous with a teleprinter you have to do the reverse calculation.