FSAE Electric Questions

[Penn Electric Racing]

Hi all,

I'm posting on behalf of the Penn Electric Racing team at the University of Pennsylvania. We've recently taken interest in the new Formula SAE Electric competition.

We've been making some progress on converting an old chassis into an EV to serve as a testbed vehicle for our various components. Things have been going relatively well so far but we have a few questions (mostly rule-based) that we were hoping the community could help us with.

Our first concern relates to the requirement of an Electric System Advisor.

A5.3 – Electric System Advisor – Electric Teams Only – Electric teams are required to designate an Electric System Advisor “who can advise on the safety systems to do with HV electrical configuration and control systems.

We are unsure how to proceed in finding an individual that fits this description. We have already consulted our professors but finding someone with the right industry experience seems to be a bit of a struggle. If anyone has any advice or could let us know what avenues we should be pursuing it would be greatly appreciated.

Our second concern is with the grounding of our composite components.

EV4.4.2 All parts of the vehicle which may become electrically conductive (e.g. completely coated metal parts, carbon fibre parts, etc.) which are within 100mm of any tractive system or GLV component, must have a resistance below 5 Ohm to GLV system ground.

We have looked into this to a degree and our top options seem to be including an aluminum mesh within the composite itself or some type of conductive coating/epoxy. We're not sure if we're somehow missing an obvious solution and were curious to see what other EV teams have found as a solution.


Lastly, we were wondering what kind of relays any EV teams are using for accumulation isolation. So far, the only suitable unit we have located is the KILOVAC EV200 Series Contactor With 1 Form X
Contacts.



Thanks for any help that you would be able to provide! As a fledgling team, we hope that the community can help us with our initial speed bumps and we hope to see you at a competition in the future!

[jlangholzj]

Originally posted by Penn Electric Racing:
Hi all,

I'm posting on behalf of the Penn Electric Racing team at the University of Pennsylvania. We've recently taken interest in the new Formula SAE Electric competition.

We've been making some progress on converting an old chassis into an EV to serve as a testbed vehicle for our various components. Things have been going relatively well so far but we have a few questions (mostly rule-based) that we were hoping the community could help us with.

Our first concern relates to the requirement of an Electric System Advisor.

A5.3 – Electric System Advisor – Electric Teams Only – Electric teams are required to designate an Electric System Advisor “who can advise on the safety systems to do with HV electrical configuration and control systems.

We are unsure how to proceed in finding an individual that fits this description. We have already consulted our professors but finding someone with the right industry experience seems to be a bit of a struggle. If anyone has any advice or could let us know what avenues we should be pursuing it would be greatly appreciated.


Surely you must have a professor in the EE dept who specializes in DC motors, Power systems, etc. If you don't have someone who does I'd be surprised that someone there wouldn't know who to talk to.

[Paul Achard]

Is it for this year? If so how did you complete your FMEA without an ESA's signature?
Otherwise, I would try to find an electrical engineer who has recently graduated from your faculty (or one that you know). I imagine they would be most willing to dedicate some time to your team.

[BeunMan]

Concerning your second question: I'd use copper but that's the way to go.

[TMichaels]

Hi!
Regarding the ESA: It does not have to be a professor or the like. A graduated engineer working in the industry for example will do if he is experienced with HV systems in general.

Regarding the grounding rule:
Copper mesh is often used, but some teams also manage to build their CFRP parts without and still meet the resistance requirements or they use GFRP instead.

Regarding AIRs:
Many teams use the Kilovac, but there are other options out there. You just need to do some research or wiat for some more teams to respond.

[JulianH]

I'd suggest to look at the Forum of FSG.

The Electric section there contains some really good threads. Especially concerning grounding, which was a major issue last year.

We measured our CFRP Monocoque of 2011 (without any additional "grounding features" like Copper mesh) with less than 5 Ohms to ground.

I think the 100mm circle is small enough to have this value. You could use your SES test beam (or some other probe) to check the resistance of your Carbon.

And of course there are a lot of experienced teams / team members in Europe (especially in the FSG board) that are willing to help you.


Regards,
Julian

[Penn Electric Racing]

Thanks everyone.

With regards to the ESA, we are working towards the 2014 season so it's not become a problem yet. Our EE professors are mostly interested in embedded systems, controls, nanoelectronics, etc. None have any decent power electronics experience or interest. We will try to contact some former students in industry but I'm not sure I have high hopes. Has anyone ever had success getting an engineer in the wild to help? We have some contacts at Tesla but that's a bit of an issue as they are on the west coast, while we're on the east.

Julian: do you use special epoxy to get that low of a resistance? We measure between 10-50 Ohms without our aluminum in the layup. With the aluminum, we can get to around 2 Ohms across a large distance if you press hard enough with the probe tips. What do you mean by "the 100mm circle is small enough to have this value?" Doesn't any point on the component have to be conductive to any chassis point arbitrarily far away?

Also, I cannot access the FSG forums - I've registered and can log in at formulastudent.de, but the forum link (https://www.formulastudent.de/fsg/forums/) just leads to a page with no links on it, no iframe or anything.

[TMichaels]

Also, I cannot access the FSG forums - I've registered and can log in at formulastudent.de, but the forum link just leads to a page with no links on it, no iframe or anything.
I just clicked on that link in your post and it works totally fine for me.
If you are still experiencing issues then shoot a mail to webmaster(at)formulastudent.de and I am sure we will be able to figure out what's wrong.

[JulianH]

Is it possible that the user must be in a team to access the FSG forums?

When I'm not logged in, this message appears:
Forum access is restricted to registered team members and officials.

So maybe you can try registering your team and then set yourself to team member status.


Our ESA is a former team member of our team, so we didn't need to search in the wild.

There must be some kind of HV-experienced professor at your university I guess. Or you could ask your sponsors (e.g. the company that provides your inverter or your charging tool).

To answer your question: We didn't use a special epoxy. It was the "standard" CFRP from SGL with an aluminium core. And even bulkhead to ground was < 5 Ohms.

50 Ohms sounds like a lot... But maybe Tobias can give you some insights in how to do it http://fsae.com/groupee_common/emoticons/icon_smile.gif

[TMichaels]

Is it possible that the user must be in a team to access the FSG forums?

When I'm not logged in, this message appears:
Forum access is restricted to registered team members and officials.

So maybe you can try registering your team and then set yourself to team member status.

I must admit that I don't know this for sure, but I know who I have to ask http://fsae.com/groupee_common/emoticons/icon_smile.gif

Regarding the grounding:
I of course know what the teams do from their ESFs, but I am not allowed to tell you to protect the IP of the teams. Thus you will have to wait for teams to post their "tricks", sorry.