Making a 60KW dynamometer - Page 1
Forum section: electronics / projects

author: shamooooot
author_rank: Regular Contributor
timestamp: October 09, 2024, 07:07:17 pm
content: Hello wonderful membersI am planning to make anACdynamometer to test 4-cylinder engines with the following specifications:- Power max.: 60KW, at 5000rpm speed.- Torque max.: 210 N.m.I will be getting a 3-phase AC induction motor, however I am more worried about the load and about the way to control it and I would appreciate any help.The 60KW seems like too much to be dissipated and controlled, and I am not allowed to use the gird..

author: BrokenYugo
author_rank: Super Contributor
timestamp: October 09, 2024, 07:17:43 pm
content: Open water tank and multiple water heater elements? Up to 4.5 kW@240V for under $20/per.

author: joeqsmith
author_rank: Super Contributor
timestamp: October 09, 2024, 07:31:11 pm
content: I had a friend who raced vintage cars that were in this range. We built a small dyno to test / break-in the engines. The first attempt used a Clayton absorber. The last one used a Stuska. As previously mentioned, these were water brakes. We used car radiators / fans for cooling, with a very large tank. It worked well.We were talking about using an truck brake at one point. I did make a small scale model of it to develop the software. Fun project. Not sure I could be of any help but keep us posted.

author: moffy
author_rank: Super Contributor
timestamp: October 09, 2024, 08:35:43 pm
content: Just an FYI, really large locomotive dynos use a large water tank filled with salt water and two separated stainless steel plates that are controlled by a servo as to how far they dip in or out of the tank, thus controlling the impedance.

author: Andy Chee
author_rank: Super Contributor
timestamp: October 09, 2024, 08:37:05 pm
content: Quote from: shamooooot on October 09, 2024, 07:07:17 pmThe traditional way of implementing an engine dynamometer is with a water brake. Forget the resistive heat dissipation.

author: langwadt
author_rank: Super Contributor
timestamp: October 09, 2024, 08:39:43 pm
content: Quote from: joeqsmith on October 09, 2024, 07:31:11 pmI know a guy who build and refitted electronics on alot of dynos, they are usually inertial sometimes combined with a telma brake

author: jbb
author_rank: Super Contributor
timestamp: October 09, 2024, 08:48:41 pm
content: On controlling the dyno:You mentioned using an induction motor as part of the setup. Are you planning to use a Variable Speed Drive (VSD) aka Motor Drive to control the motor?If so, talk to your vendor about your specific application. Hopefully you can get together with an applications engineer. Features of interest:- operation as a generator (not a rare feature)- ability to turn on the VSD while the dyno is already spinning (not a rare feature)- braking options (not a rare feature); many units have a built in brake ‘chopper’ which can be connected to an appropriate resistor bank to do just what you want.On power dissipation:- a big bank of air cooled resistors will definitely work but could be quite expensive- water cooled resistors will be smaller and could be cheaper, but then you’ll need water pumps and pipes and tanks. As others have said, car parts like radiators could be helpful here- remember that 60 kW of heat is a whole lot and will heat up a room real fast. It may also overwhelm air conditioning systems. Consider putting your resistor bank (or at least the radiators) outside- if you have an open water tank with heater resistors, remember that once it gets hot it’ll dump water vapour into the air, which could then condense all over the place where you don’t want water…Edit: typo

author: joeqsmith
author_rank: Super Contributor
timestamp: October 09, 2024, 09:16:32 pm
content: Similar to what we were considering. From what I remember, they are limited on the RPM. In the end, we wanted to support steady state for brake ins. The model I made for it had constant RPM and constant torque.https://www.porgest.cz/en/products-and-services/modification-and-service/electromagnetic-break-telmaThe Freightliner factory in Mt Holly was using resistive loads. That was a crazy setup. They would chain the trucks onto a wheel dyno as part of a final test. That would throw off some major heat. Cummins had mostly absorbers but a few motoring dynos as well (hard to do with water). For my friend's vintage cars, motoring was never a concern and water was easier to handle.I've seen a few using hydraulics (oil) as well for marine use.I wonder if you looked at the small water brake systems like Land & Sea? They offered them for motorcycles, snowmobiles and such. I thought about getting one for my motorcycles at one point but end the end, I just data logged the crap out of the bike to see what was going on.

author: langwadt
author_rank: Super Contributor
timestamp: October 09, 2024, 09:54:18 pm
content: 5000hp dyno for a gasturbinehttps://youtu.be/yY73rm7FZhM?si=T7N4fHFo8Okj_CQ5

author: CaptDon
author_rank: Super Contributor
timestamp: October 10, 2024, 02:55:29 am
content: We ran our 4500HP GE locomotive prime movers at the Southwest Research Incorporated test facility in San Antonio Tx. It was some sort of a water cooled inductive brake. The higher the D.C. current applied the higher the torque loading. There were no load resistors. I think it was built like an internally short circuited alternator with the stator being water cooled and the armature being excited with D.C. just like a car alternator. I believe the 'Mustang' brand 'in floor' chassis dynos work on the same principle. I know a very famous exhaust system engineer who had a water brake dyno. They broke the coupling shaft which exited through the corrogated metal roof and landed in a neighboring field!! Be safe!! The control room was on the other side of a double thick cinder block wall. No windows, only CCTV cameras. They were doing drag racing engines which tended to blow up when the timing was pushed to far.

author: NiHaoMike
author_rank: Super Contributor
timestamp: October 10, 2024, 04:55:50 am
content: Take a second engine and convert it into a large air compressor?

author: Berni
author_rank: Super Contributor
timestamp: October 10, 2024, 05:35:52 am
content: AC Induction motors are the worst kind of motor to use for this application.These motors do absolutely nothing if they are spin up with the terminals unconnected. They only turn from a glorified flywheel into a electro mehanical machine once power is applied to the terminals to create a magnetic field inside it. Hence you need a large VFD drive that is also has support for a resistive load dump. So this not only means having a pretty sizable motor for 60kW but the VFD needs to be quite a chonker too.Now you could cheat a bit by supplying 1 phase of your motor with DC power. This turns the rotor into a eddy current magnetic brake. Quite an effective one too, however all the power is getting dissipated inside the rotor. This is the smallest and most difficult to cool part of the motor. So while you could use this as a dyno absorber, the dyno run would have to be kept short enough to not melt your aluminium rotor while needing a very long time between runs to cool it back down.DC motors are the easiest to use as a electrically controlled brake as you simply have to connect a resistor across its terminals. Similar can be done with synchronous AC motors, even better if it is a externally exited AC synchronous motor. For those you just hang some massive heating elements from the 3 phase output while applying variable DC power to the excitation coils, more excitation you apply more output voltage you get and more load you get. Giving you a nice bonus of being able to control the high power part using a low power 'signal'.But in general the 'water brakes' are the preferred method for engine dynos. They are just simply purposely inefficient water pumps. Very easy to produce as they are just a bunch of CNC machined metal parts screwed together (without the need for any tight tolerances) and they can absorb a huge amount of power continuously for even fairly small units. A water brake the size of a small microwave could easily dissipate 1000kW as long as you can keep the water flowing trough it cooled. They also have a pretty wide controllable range with the correct design (some control the water restriction, some control movable vanes inside the pump)

author: ftg
author_rank: Frequent Contributor
timestamp: October 10, 2024, 08:23:28 am
content: The Finnish moped builder Asoftaaja built is own dyno to test and tune the engines he builds.There is a lot to do better in that build, so it could be possible to scale it up to your purposes.

author: Jeroen3
author_rank: Super Contributor
timestamp: October 10, 2024, 09:26:32 am
content: I've heard of people doing it with standard brushless generators (generally available) with current limit control in the excitation system.They connect it to a large resistive loadbank (rental stock) and you can test motors that fall within the rpm range of the generator.Since the control is electrical you can change the load.The same can also be done using async motors and four-quadrant drives, but 60kW gets tricky really fast when you start considering grid codes.

author: Wolfram
author_rank: Frequent Contributor
timestamp: October 10, 2024, 11:45:32 am
content: Synchronous generators are much easier to use here, as they don't require any excitation to have a rotor field. I'm not sure if an induction machine can be made to generate power into a resistive load bank without any active inverter between. I know people have managed to get induction machines to self-excite by putting capacitors in parallel with the windings, but this relies on residual magnetism in the rotor for startup, and this magnetism can be lost if they are slowed down with the load attached. You can brake induction motors by applying DC to the windings but then most of the mechanical power gets dissipated in the motor itself, making it impractical at the tens of kilowatt scale we are talking about here.Most (but not all) EV traction motors are synchronous (IPM construction, reluctance + PM). These are pretty cheap on the scrap car parts market, and one of these would make a nice dyno if hooked up to a resistive load.

author: CaptDon
author_rank: Super Contributor
timestamp: October 10, 2024, 01:16:37 pm
content: Thank you to a previous poster for mentioning 'Eddy Current' as that is indeed what we used at SWRi and what the Mustang brand chassis dynos use. In this case the motor is kind of inside out so to speak. Applying variable D.C. to the stator of an induction motor can cause eddy currents in the rotor and the rotor acts as the brake and gets hot. The inside out version is D.C. applied to the rotor and the stator has the circulating eddy current. Think of it like a car alternator with the output short circuited. The stator is water cooled in our application. 4500HP or around 3.3MW. That is actual crankshaft output power. You could guess the total BTU input to the engine at around 12,000 Hp. At any one time in the 4 stroke cycle only about 2.5 cylinders of the 12 are adding power the rest are dragging along in the non-power producing part of the cycle.

author: joeqsmith
author_rank: Super Contributor
timestamp: October 10, 2024, 03:13:40 pm
content: Data sheet for a electronic brake with specs. Note the 5000RPM limit. Also note that you can't get high torque and low RPM. At 60kW, if you kept is at that max speed, you could run it for a decent amount of time.https://www.telmausa.com/Downloads/OC442107a.pdfVideo showing my model dyno which is a 3 phase permanent magnet generator that feeds a full wave rectifier and some FETs to provide the variable load.

author: langwadt
author_rank: Super Contributor
timestamp: October 10, 2024, 04:20:48 pm
content: https://youtube.com/shorts/DTuyDAh7NMM?si=KL3YJTVebgK5kHWT

author: hanakp
author_rank: Regular Contributor
timestamp: October 10, 2024, 09:40:11 pm
content: Reminded me of this Airbus A380 brake test video:Play it with sound, it's almost mesmerizing.

author: langwadt
author_rank: Super Contributor
timestamp: October 10, 2024, 10:32:54 pm
content: Quote from: hanakp on October 10, 2024, 09:40:11 pm5MJ/s "only" about 6700hp

author: shamooooot
author_rank: Regular Contributor
timestamp: October 11, 2024, 06:41:35 am
content: I would like to thank each and everyone of you guys, I wanted to get an idea about how the professionals do it and I really appreciate all the help.So the situation is like this:- I am not allowed to use the grid.- 3-phase AC induction motor:Std. max. speed is 3K and 75KW can be sourced for $1.5K to $2K.Higher speed motors 5.5K-6Krpm, I got quoted all the way from 4K$ to 10K$, and they are air cooled motors..- Then comes the load:I got quoted for $3K for an "Automatic Load Bank AC400V-100kW", so I am not sure if I should go for be DIY or BUY, but I am leaning toward getting it ready as it might not worth the trouble. The load is air cooled and has some features like controlling the steps with 1KW increments, protections, and DAQ software.If I used such load bank I imagine that I won't be needing any controllers for the motor, such as a two-quadrant converter.The prices are from Chinese vendors, and the motor is the main concern as it is expensive and might be not what they claim..

author: Berni
author_rank: Super Contributor
timestamp: October 11, 2024, 09:41:43 am
content: You won't be able to just pair together a load bank and a 3 phase induction motor. It needs a VFD in between.You need to use a synchronous generator for this. Preferably one with external excitation so that you can pump up its output voltage at low RPM and reduce it at high RPM so that your 3 phase voltage stays within a reasonable range for the load bank (it otherwise won't be able to apply full load at low RPM).If you are after cheaply cobbling together something then you can go get a big hydraulic pump (like the ones found in excavators) from a scrapyard and pipe it trough a high pressure restriction valve into some radiators to cool the oil.Going electrical with this will be fairly expensive no matter what way you put it as the thing you are trying to do is not quite that standard, and involves a fair bit of copper for the powers you are looking at. Your best bet at doing it electrically on the cheap is finding a large diesel generator to steal the synchronous generator out of and then coil a bunch of wire in a water filled barrel as the load.

author: shamooooot
author_rank: Regular Contributor
timestamp: October 11, 2024, 04:25:51 pm
content: Quote from: Berni on October 11, 2024, 09:41:43 amThank you so much.To be honest I invested my time and communications in the AC induction motor and didn't think at all of the synchronous motor.I am not sure the synchronous generator are available at 5K-6K rpm max. speed.Regarding the AC induction motor, I still don't see a need for a regen VFD, these VFD's at the power we are talking about are too expensive.. Here is a company that offer a Regenerative Drives, and a Non-Regenerative Drives dynos:https://dynesystems.com/products/drives/For the modes of dyno:Constant SpeedConstant LoadConstant PowerSweep TestI think, but not 100% sure they can all be controlled through the load.

author: johansen
author_rank: Super Contributor
timestamp: October 11, 2024, 05:58:08 pm
content: All large VFDS have a brake transistor (igbt)You can easily find resistors to dump the heat if you don't want to buy the one that comes with the vfd. a 100hp vfd can be found for around 5Kusd, you may be able to find used surplus for free.I would trust a standard 3600 rpm 30 hp induction motor to run at 5K rpm and deliver 60KW of load to the engine. the motor will be generating about 52-55KW worth of heat after accounting for losses in the motor and the VFD. -it may not be able to handle this continuously but it probably can with a water drip feed on the external shell. If the vibration is bad, just pull the rotor and send it to a company to be dynamically balanced.to get 60kw out of a 240v motor at 5k rpm you'll need a 480v vfd, not a 240.so you're dealing with a 750 volt DC bus and brake resistors.or you rewire the motor for 138V delta and then you can run a 100hp 240v vfd.https://www.surpluscenter.com/Brands/Baldor/30-HP-3510-RPM-230-460-Volt-AC-3PH-Baldor-Motor-10-3253.axd--400$controlling the load is going to be a little hard. the engine is going to generate max torque but the rpm will only rise if the VFD lets it. so you have to tell the VFD to increase the frequency to let the engine increase in speed.-if the engine can overcome the typically 2X rated break down torque of the induction motor, its going to run away and the VFD will shut off due to overcurrent.which means that you have to measure the torque on the motor by the engine, and slowly work up to wide open throttle. you will not get reliable real time information out of the load power because the power factor, voltage, losses in the motor, are all very hard to predict unless you have real time information on both the power delivered to the load (which is pwm'd to keep the bus voltage down) and the current and voltage information in the motor.. and you have to account for the inertia stored in the motor if the rpm rate of increase is significant.so just measure the torque and log it against rpm.It is also possible to just use capacitive excition and a resistor bank on the induction motor. you're going to need a three phase servo powered variac to excite the motor with an active control loop. you still will have to measure the torque on the motor by the engine. --this will be the cheapest way to go.Induction motors are about 30% reactive as a generator highly loaded. so you need 3x 20 amp 240v variacs ganged together and about 2000uf x3 worth of caps rated to 480v and then you need a 1-2-4-8-16-32KW resistor bank (you don't need perfect balance between the phases) to swich through 1KW, 2,3,4----63KW worth of load resistance.a motor re-wired for 138v delta may allow you to use standard 0-140V variable transformers to manage the capacitors, but you're going to need 40 amps worth of them instead of 20.in theory you can just use a whole bunch of 10$ 2 pole hvac contactors to manually switch out a large bank of capacitors. the contactors won't last all that long.. (thousands of cycles) due to the very high inrush current.. but it will be cheaper than buying 3x 40 amp worth of variacs and trying to drive them with servos.

author: shamooooot
author_rank: Regular Contributor
timestamp: October 12, 2024, 11:57:04 am
content: Quote from: johansen on October 11, 2024, 05:58:08 pmThank you very much johansen for all the very good details. It took me some time to digest it..I made some assumptions with my best understanding:- Engine:• Power output: 75hp (55 kW)• Torque: Up to 215N·m- Dynamic torque sensor to log power, speed, and torque.- The power where I am is 400V, 50Hz.For the VFD option:I found this 90hp example: GK3000-4T0900Ghttps://www.ato.com/125hp-vfdThe brake resistor they mentioned for this specific model: 20*3ohm, 18000W. I imagine such resistor (if it can be found) might cost $1k to $2k.Most VFD with brake (Brake chopper) option datasheets don’t mention the value and sizing of the braking resistor.For the Variac:• Variacs: "3x 25A 400V" to control the voltage and hence the reactive power. Each varaic of the 3 should have 10KW power.• Capacitors: 2000µF x3, 600V rated to compensate for the reactive power of the induction motor when heavily loaded.• Switchable Resistor Bank: 1-2-4-8-16-32 kW to control the load.• Speed is controlled by the engine and fine-tuned with the variacs..For the "active control loop", I understood it as a way to choose when to connect/disconnect the capacitors through perhaps measuring voltage, current, and power factor.I see the motor you shared have: Voltage 230/460 AC, but Frequency 60 Hz, I think it won't be a problem to use it with the VFD but I am not sure about using the same motor with the variac setup.

author: johansen
author_rank: Super Contributor
timestamp: October 13, 2024, 12:47:15 am
content: Induction motors do not have an intrinsic voltage. They have a soft saturation volts per hz limit.A 400v 50hz motor is going to be producing 800 volts at 100hz, if you let it.. that is if you need it to. Torque follows the volts per hz squaredA european 380v 50hz motor at 50hp is an american 480v 60hp 60hz motor.

author: NiHaoMike
author_rank: Super Contributor
timestamp: October 13, 2024, 04:37:58 am
content: I'm still thinking that compressing air with a second modified engine would be far more practical. At the least, the problem of dissipating the energy is as simple as just blowing it outside.

author: langwadt
author_rank: Super Contributor
timestamp: October 13, 2024, 09:58:13 am
content: Quote from: NiHaoMike on October 13, 2024, 04:37:58 amor just get a telma retarder, something like this:https://www.telmausa.com/Downloads/OC442107a.pdfit is also reasonably simple to control because you just need PWM, often just a dimmer and a rectifier

author: shamooooot
author_rank: Regular Contributor
timestamp: October 13, 2024, 10:15:52 am
content: Quote from: johansen on October 13, 2024, 12:47:15 amThank you again for you reply. And for helping me better understand it.400V/50Hz =8V/Hz , then 8V/Hz×100Hz=800V that's 6000rpm for a 2-poles motor. And the same ratio could be applied to switch calc. between European and US motors.If we capped the motor/engine to 4000rpm top speed, it would mean67 Hz73 Hz with the safety margin, and533 V578 V. This would greatly limit the VFD options..The torque for the Baldor motor is approximately 60.73 Nm, which means the breakdown torque will be around 120, while the engine torque could reach 185-210 Nm. So it might not be a good fit for this engine.Going back toBernireplies, a synchronous generator could indeed save me a lot of troubles, especially that I need less than 100VDC and couple of amps to control it and I would still need the load bank..It seems to be hard to find synchronous motors that have such high speeds, and motors at that power and torque seems to be too expansive, but perhaps I am assuming wrong, here are two example motors:75kw 6000rpm is 119Nm/75kw 5500rpm is 130Nm: $6K132kw 5500rpm Torque is 229Nm: $9K

author: shamooooot
author_rank: Regular Contributor
timestamp: October 13, 2024, 10:38:54 am
content: Quote from: langwadt on October 13, 2024, 09:58:13 amInteresting and indeed could be the safest option as they only might require cooling, I also noticed they come with their own ECU, and could be get used for around $4Khttps://www.ebay.com/itm/186265022860, I wonder how much the new ones are?Also compared to motors how are their range with speed and load, and control precision etc..

author: langwadt
author_rank: Super Contributor
timestamp: October 13, 2024, 11:05:03 am
content: Quote from: shamooooot on October 13, 2024, 10:38:54 amdoesn't look like that are that much more newhttps://www.store.telmausa.com/en/retarders/

author: Berni
author_rank: Super Contributor
timestamp: October 13, 2024, 11:22:20 am
content: Yep those electromagnetic retarders are pretty much what you want.You likely won't find a synchronous generator for the exact specs you want since they are designed to run at a fixed RPM (usually driven by a large low rpm diesel engine) so you would need to 'qualify' it for your application. As said with external excitation you can control how they behave, so you can make it operate at RPM very different from the design RPM. The only limitation is how fast you can spin the rotor without it exploding from centripetal forces and what the bearings will handle. Overspining it will also make it less efficient due to the eddy losses going up from the higher frequency, but overspecing it should give it enough cooling to handle 200Hz no problem. But you could extend the RPM range by attaching a automotive manual gearbox to it and selecting the appropriate gear for the RPMs you want to run at.But yeah those retarders are the same thing except that the 'load resistors' are integrated in the same device. You need a similar supply to run the coils as you would to run the excitation coils in a synchronous generator, just that the current it generates is eddy currents rather that current put on terminals to go into the load bank. This makes it a cheaper solution since you need less parts and they are designed to run at a range of RPMs. The downside of these particular ones is that they are air cooled and so can only provide max braking force for a short period of time before the rotor gets too hot (hot rotor = higher resistance = less eddy currents). So you likely want to overspec it a fair bit and maybe add some blower fans to help cool it after the run when it is not spinning anymore. As mentioned earlier in the thread real dynos solve this by instead magnetizing the rotor, making eddy currents in the stator and then cooling the stator with water.But id say such a retarder has a reasonable chance of being found in a scrapyard in unknown condition for cheap. Not much to go wrong in one, either bad bearings or toast coils, both can be rebuilt yourself.

author: langwadt
author_rank: Super Contributor
timestamp: October 13, 2024, 11:34:21 am
content: Quote from: Berni on October 13, 2024, 11:22:20 amthis one has specs for cold,3min,+60minhttps://www.telmausa.com/Downloads/OC442107a.pdfand at some point cooling the engine your are testing also becomes an issue

author: Jeroen3
author_rank: Super Contributor
timestamp: October 14, 2024, 11:14:22 am
content: Belts are a thing often used to adapt the speeds for synchronous machines. Very common, and widely used.Truck PTO have them a lot and direct drive diesel trains have them for on board power generation.The only drawback is their torque limit and slipping. But otherwise easy to put together.

author: max_torque
author_rank: Super Contributor
timestamp: October 14, 2024, 01:48:14 pm
content: Few notes from me, as some on with over 30 years engine and chassis dyno experience between 5bhp and 5,000bhp!1) If the actual plan is to test engines, just buy a COTS engine dyno. This way you can get on with actually testing engines (rather than waste thousands of $$ and hours developing a dyno, which is a completely pointless activity if the aim is to test and develop engines. Second hand dynos of all types pop up now and then. In reality the dyno itself if mearly one of the systems you will have to install and develop, especially if you want any measure of precision and repeatability2) If you want a quick and dirty solution to mearly load and engine for a short period, then a hydraulic motor and restrictor (needle) valve provides a way to produce a huge reaction torque as a hyraulic motor the size of a ice cream container can often do 1,000 Nm or more at 100bar!. Heat is your enemy, but because you are not really using dyno parts, those parts are cheap and generally available second hand. This system cannot be run continuously without cooling of course, but it can work for short periodsPersonnally however, just buy a dyno and get on with it, otherwise you'll spend 99% of your effort being a dyno developer and hence only spending 1% of the remaining time on your actual engine...

author: shamooooot
author_rank: Regular Contributor
timestamp: October 16, 2024, 07:07:33 am
content: Thank you guys, I appreciate it..I am still looking into the synchronous option, perhaps as johansen mentioned a 3600rpm rated motor can survive 4000rpm. The engine specs mentions (Speed at maximum power 4000(rpm)).As this won't be used as an actual generator or tied to the grid and the power would be dissipated to a load the job doesn't look complicated. Especially, that these motors are fairly common and could be found at a good price.Also, I don't really understand how long a test can be carried using the eddy current option before it loses its efficiency. Or how big of an eddy current brake should be get to stay safe for the specified engine..

author: shamooooot
author_rank: Regular Contributor
timestamp: October 30, 2024, 08:34:32 am
content: Hello AgainI did some search in my local area and I actually found surplus induction motors and VFD's, the prices are really good and could be cheaper than any other option.I came across a paper that describes almost exactly what I needhttps://repositorio.comillas.edu/jspui/handle/11531/17559but I am not sure about some few things..From the paper:QuoteWhen sizing the motor and hence the VFD the author uses the the range of speed at peak torque, so if my engine peak torque is at 1500rpm, then I should aim for 1500rpm motor for minimizing slip and maximizing stable power output and no reducer should be required. The rotor speed need to exceed the synchronous speed to enter negative slip so the motor absorbs power.Power P=T×ω will be 29.06kW, and current will be 56.7A (Voltage: 400 V, Power Factor: 0.85, Efficiency: 0.90)So a 4-pole, 30kW, 1500rpm, 190nm asynchronous motor should be sufficient.The braking resistor calculated on (page 47) is 8Ohm and 47kW, assuming duty cycle is going to be 100%!.Are these assumptions valid, or am I mistaken?!

author: Jeroen3
author_rank: Super Contributor
timestamp: November 01, 2024, 03:38:15 pm
content: The braking resistor is going to need to be able to takeall input shaft power, maybe even more to keep the dc link voltage of the converter within limits.I've seen a setup like this only once and they were using 4-quadrant capable siemens drives capable of injecting back to grid.

author: johansen
author_rank: Super Contributor
timestamp: November 01, 2024, 06:11:29 pm
content: Quote from: shamooooot on October 30, 2024, 08:34:32 amso peak torque is usually 2/3rds peak rpm, so you can get by with a motor sized for the torque and just run the motor out past its design volts per hz limit (keep in mind torque and slip follow the volts per hz squared)So I still think you can run a 30hp 1800 rpm 240/480v motor re-wired for 138 volts delta, out to 4500 rpm and run it off a 100hp 480v vfd, and i believe the motor can handle this just fine. the vfd will be able to provide 480v at 100hp and this corresponds to 6200 rpm at the base volts per hz curve of the motor. you should be able to get 100 hp out of a 30hp motor, at 6200 rpm. this is 76KW.sending the rotor out to be dynamically balanced is not an option at 6200 rpm, but you can probably get by with a stock, good quality 1800 rpm motor, running it out to 4500 rpm.your dc brake resistor needs to be sized to handle the60KWyou expect to get out of the motor. at 750 volts that's 80 amps or about 9 ohms.

author: shamooooot
author_rank: Regular Contributor
timestamp: November 05, 2024, 11:26:38 am
content: Quote from: johansen on November 01, 2024, 06:11:29 pmThank you johansen, I was suspicious about the mentioned details in the paper and I couldn't find if they actually did make the system and if it worked as intended or not..So I need to find 208/240V, 50/60Hz, 1500/1800rpm, Y connected, 30kW induction motor, and connect it as delta, but this might be tough to find.Or I get a 3000rpm/380V motor and run it above 3000rpm without exceeding the rated voltage of the VFD.I found these motors locally (but it was when I was looking for higher power):https://ibb.co/NNsJhWGhttps://ibb.co/zVwcTz4https://ibb.co/0JNF85Xhttps://ibb.co/6rP4d85https://ibb.co/m5bMS1NAlso I would like to ask do I actually need such a beefy VFD (100hp)?Engine:Max. Power: 55kWTop Speed: 4000rpmMax. Torque: 185NmSpeed at max. Torque: 1500rpmTHANK YOU

author: johansen
author_rank: Super Contributor
timestamp: November 05, 2024, 08:09:00 pm
content: Quote from: shamooooot on November 05, 2024, 11:26:38 amyou need a bigger vfd than the motor so you can overvolt the motor to get enough torque, when you exceed the base rpm.so you need two things, you need a motor that can handle 55KW at 4000 rpm and you need a motor that can handle 39hp at 1500 rpm. this corresponds to a 50hp motor at 1800 rpm.a 100hp vfd will be able to drive a 50hp motor re-wired for half the nominal volts of the motor, which doubles the current flowing. you have to do this so that the motor can be driven with enough voltage at the high end of over 2 times the base speed.induction motors produce or consume torque proportional to volts per hz squared.