It has to withstand a 50G shock - insight into eLION development

00:00:00: Hello everybody and welcome to a new episode of our WorshrexRod Tech Podcast.

00:00:08: My name is Robert Weber and my guest today is Dr. Thomas Finkin.

00:00:12: Thomas, welcome to the podcast.

00:00:14: Thank you.

00:00:15: Hello.

00:00:16: Please, before we start talking about E-Lion and your electric drives, introduce yourself

00:00:22: briefly to the listeners.

00:00:24: Okay.

00:00:25: My name is Thomas Finkin.

00:00:26: I'm with WorshrexRod since 10 years now.

00:00:30: My technical background is electrical engineering.

00:00:33: This is what I did and followed by a PhD study regarding this topic, electrical machines.

00:00:39: So your heritage is industrial automation.

00:00:41: This is what I started with here, but since eight years now I've been busy and dealing

00:00:47: with the electrical machines for mobile machinery.

00:00:51: So we want to talk about electric drive solutions by WorshrexRod and we already had

00:00:56: an episode with Peter and he explained the basics.

00:01:00: And now we want to go a little bit more into details.

00:01:04: On one hand the mechanics and on the other side the electric magnetic.

00:01:09: So let's please start with the mechanics.

00:01:11: What is so special with your electric drive solutions?

00:01:16: Yeah.

00:01:17: So the main and crucial issues we have with our design and our specifications is that

00:01:25: we are developing a heavy or did a development for a heavy duty.

00:01:32: Heavy duty means that we are facing heavy environmental loads such as mechanical loads,

00:01:40: shock and vibration, that there is a huge range of temperatures you are facing.

00:01:47: And of course the tightness of the motor is suitable to withstand all the conditions

00:01:52: that you may think of environmental usage of a mobile machine.

00:01:57: So water, spray water, splash water, ice water, splashes, water immersion.

00:02:03: But the main topic is vibration, right?

00:02:06: This is the main topic and this is totally different to what we are used to in industrial

00:02:11: motors, industrial applications.

00:02:14: So shock and vibration.

00:02:15: So we are talking about a 10G vibration.

00:02:19: 10G.

00:02:20: And shock as a single shock up to 50G.

00:02:27: Single shocks means specification is that we are testing with three shocks per axis

00:02:33: with 50G and recurrent shocks of 25G.

00:02:38: And this is what we are testing thousand times per axis.

00:02:41: I want to talk a little bit about testing and engineering this housing and how do you

00:02:47: proceed, what have you done in case of material design, test setup, inner workings.

00:02:55: How do you proceed?

00:02:56: From the very beginning we started with simulations, structural mechanical simulations to start

00:03:03: with maybe harmonic analysis to learn about the eigen frequencies and those results then

00:03:10: were used to especially calculate those vibration loads specified, those 10G in the range of

00:03:20: the eigen frequency.

00:03:21: So then you know that in this resonance the load is worst case.

00:03:28: So if you accelerate on your A side of the motor, which is the flange, all those mechanical

00:03:35: loads are just used into the motor this place.

00:03:39: You know that on the B side of the motor and at the other end you have 10 fold, 20 fold

00:03:47: those accelerations that you feed into the motor on the A side.

00:03:52: But how you handle that?

00:03:53: This is mechanical strength how to overcome those issues.

00:03:57: But we started with a simulation to keep the testing effort and the sampling effort as

00:04:01: low as possible.

00:04:04: So many simulations done, but you can do simulations for all as long as you don't know that this

00:04:12: is the right thing that you are simulating and calculating, it's worth nothing.

00:04:17: So in the end of each sample phase we did many testing efforts to evaluate simulation models

00:04:25: we have.

00:04:26: You tested this in law here?

00:04:29: This was done in external test labs all over Germany because there are only few shakers

00:04:38: available.

00:04:39: Shakers are the testing machines?

00:04:41: This is a testing machine to test the shock and vibration and our machines are heavy and

00:04:49: the shock load is high and the vibration load is high.

00:04:54: So there are only few shakers available who could test this.

00:04:59: So we were forced to do those tests in external test labs.

00:05:03: Can you please describe some problems you recognized when you started simulating or

00:05:09: testing and what you changed during the development process?

00:05:13: So most of your problems we had were those resonances I named before.

00:05:19: So in case of resonance the resulting acceleration within the complete body structure of the

00:05:25: motor was so high that we experienced many failures.

00:05:31: So broken screws, leakages in the housing, broken structures.

00:05:36: So we had to do a lot of duration loops to overcome those issues, strengthening the

00:05:43: bolts, strengthening the...

00:05:45: Was it a surprise for you?

00:05:47: This was a surprise in that way that we underestimated those resonances and all those forces and

00:05:54: stresses that occurred during sinusoidal vibration.

00:05:57: Yes, that was a surprise.

00:06:01: That was a surprise.

00:06:03: What is now the USP of the Bosch Rexwood housing?

00:06:06: I would call it...

00:06:08: What is so special now when you look at the market?

00:06:12: What is the difference to other companies?

00:06:14: What do you have to offer?

00:06:15: So I would say in terms of the housing it's the mechanical strength.

00:06:20: The overall mechanical strength we evaluated many, many applications and standards and we

00:06:30: specified an envelope function covering all those applications.

00:06:36: To have a motor with a robust design that is suitable to withstand all loads you can

00:06:42: think of in mobile machinery.

00:06:45: Let's talk about the electric magnetic.

00:06:48: What is different or which customer pain do you solve there?

00:06:54: So we are in the very beginning we were thinking of and discussing what would be the right

00:06:59: motor to design and there are many, many options.

00:07:04: Our target was to develop a motor that is suitable for traction drives as a main application

00:07:13: as well of course for all the others but if you could handle the traction you could handle

00:07:20: all other applications as well.

00:07:23: So what is so special about traction?

00:07:26: If you think of a heavy working machine that wants to accelerate

00:07:32: Maybe on a slope full loaded you need high talks high talks at low speed

00:07:37: To accelerate the vehicle from a standstill to and speed so high talk at low speed

00:07:45: But on the other hand different the difficult this is yeah, but this is

00:07:50: Most motors aim to have as most

00:07:54: Talk as possible. Yeah, this is what I would have done ten years ago as well

00:08:01: Yeah, but on the other hand, you know that it's a new paradigm the speed. Yeah, it's different because

00:08:07: each vehicle must reach a

00:08:11: maximum speed as well so and

00:08:15: Having at this maximum speed as much as power as possible is

00:08:21: a

00:08:23: requirement that

00:08:25: describes the traction or the the motor used for traction applications

00:08:29: Yeah, so we're talking about the constant power speed range

00:08:33: describing

00:08:35: this range of

00:08:37: speeds of the motor

00:08:39: Starting from the rated speed the edge speed up to the maximum speed of the motor and our

00:08:46: specification is to have within this speed range

00:08:50: Minimum of 80% of the rated power as an output still and

00:08:56: The ratio from rated speed to maximum speed. This is

00:09:01: specified for our motors of

00:09:03: Ratio of one to four is the ratio of rated speed to maximum speed

00:09:09: This is a design criteria that we defined as a traction drive and this is what we fulfilled in the end

00:09:16: How do you manage that? What is it under the hook what you did there?

00:09:21: So the main topic there is of course the electromagnetic design when thinking of the torque

00:09:28: Which is proportional to the magnetic flux and the current if you want to increase the torque density you have

00:09:36: Two options first to increase the current or on the other hand the magnetic flux

00:09:42: The current often is limited by a system meaning battery or the inverter

00:09:49: Limits of the current so what can you do is to increase magnetic the magnetic flux?

00:09:55: But if you increase the magnetic flux, we may have a problem at higher speeds because

00:10:01: Rotational field of the rotor induces voltages to the stator winding and

00:10:06: Once you reach the voltage limit you cannot further increase the speed

00:10:12: without

00:10:15: Decreasing the rotor flux the magnetic flux so this is done by so-called field to be cunning

00:10:21: So you feed a current into the stator of the machine that counteracts the rotor field or the electromagnetic field of the rotor

00:10:29: But the the current you use for field weakening is not available anymore for talk and

00:10:37: Therefore the torque decreases over speed

00:10:41: Okay, so and the more flux the magnetic flux you have in the motor the more current you need

00:10:48: For field weakening, but how do you search for optimum? How do you optimize this?

00:10:53: this is done

00:10:56: within the design process so

00:10:58: Multi-target up to optimizations are used for those algorithms

00:11:02: Yeah to to optimize exactly and this is a a compromise between

00:11:09: This large constant power speed range and high torque densities

00:11:13: But this is now a common product right the motor

00:11:18: Maybe you can go into niches and have special applications and you will change the whole solution once again

00:11:25: Of course, yeah, and this is what we're doing right now as well

00:11:28: because the traction

00:11:30: Motor as I said before is a compromise between torque density and high speed

00:11:36: Now thinking of applications where you don't need those high speeds

00:11:40: For example pumps when driving pumps for working hydraulics

00:11:45: Hydraulic pumps maximum speed is up to 3000 maybe rpm

00:11:50: That means you don't need an electrical machine with that high

00:11:55: Rotational speeds or maximum speeds

00:11:58: So in this case you need a motor with higher talks high continuous talks

00:12:05: As high as possible

00:12:07: Without any constant power speed range. So or very small ones. Yeah, so and in this case this could be

00:12:14: Completely different design as what we have today

00:12:19: But the housing stays the same housing would be the same so we can see those as an option

00:12:26: So the internal electromagnetic parts the active parts as an option

00:12:31: one for the pump drive one for the trick and drive and

00:12:34: The housing as option as well. Yeah, so heavy duty or

00:12:40: Standard duty with reduced loads mechanical loads less shock and vibration loads at the end

00:12:47: I also want to talk a little bit about export because we have special export rules talking about dual use and

00:12:54: There you have maybe some problems with the inverter. How do you handle this topic?

00:13:00: This was a

00:13:02: specification that affected our electromagnetic design as well

00:13:06: As you said the dual use is a limitation

00:13:10: When thinking of inverters with output frequencies higher than 600 Hertz

00:13:16: Yeah, so for those you need an export control. It's very difficult. This is difficult to read much effort

00:13:23: Yeah, so our target was to develop electrical machines

00:13:28: For those that you don't need inverters with output frequencies higher than 600 Hertz and as

00:13:36: The frequency is proportional to speed and the pole pair number

00:13:43: So the number of poles in the electrical machines

00:13:45: That was a reason to reduce and have a limit to the number of poles in our case

00:13:51: It's also compromise once again. This is a compromise as well

00:13:55: Yeah, so thinking of the motors for the pump for example

00:13:58: Those are with higher pole pair numbers as you don't need those high speeds

00:14:03: Yeah, and then the 600 Hertz limit allows higher pole numbers as the speed is not that high

00:14:11: Thomas what is coming? What is the team working on or is everything solved?

00:14:16: So no, it's not solved now today

00:14:20: We have some some motors in production start-up production

00:14:24: We had with some of those motors of our portfolio

00:14:27: What we are doing right now and what we are working on is the electromagnetic design of the active parts for pump motors

00:14:36: We have different sizes available of our motor portfolio for different sizes in diameter and

00:14:41: For almost all of them. We are developing pump motors or motors dedicated to higher talks

00:14:49: Okay. Thank you very much for the pleasure. Thank you. Bye

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