Use electric cooking element for higher voltage testing?

[phillipschip]

I have this setup right now and have tested at 40v. Next step I would like is to bench test with one of my 200v battery packs. Would I leave the cooker element in the circuit or would it be of no use at that voltage? Thanks!

[Bigpie]

The cooker element isn't going to do any current limiting like that, it needs to go inline.

Its purpose in testing is if there's some issue, reverse polarity, short circuit, etc, it'll limit the current that's able to flow. How you've got it wired the current will use the low resistance path through the fuse instead.

Is that fuse rated for 200v? A too low voltage rated fuse could blow and current continue to flow

[johu]

Damn this setup even makes me a bit nervous. This is ok for sub 60V, for anything in the 400V range it offers too much bare metal to touch or drop stuff on.

The fuse is rated 30V by the looks of it. If it blows under high voltage it will disintegrate and spew molten stuff all over the place.

[muehlpower]

What is this test setup supposed to do? Do you want to discharge the current when the fuse blows?

[uhi22]

Damn this setup even makes me a bit nervous

This is *really* a sign that something is crazy. Normally Johu has no problem with bare metal at 400V. So it is *really* too much of it.
Do we have a wiki page which explains the consequences of such a test setup?

[Bigpie]

viewtopic.php?t=3931 watch the video in this thread

[phillipschip]

So sorry I wasn’t clear :0. This setup was for testing at 36v. The fuse is 100 amp, 36v. (I’ll be using a 500v rated fuse for any higher voltage testing-also, the motor is in the car and turning wheels so there is more current draw than during typical testing.) I was going on the advice in the video “how not to kill a Tesla drive unit" (around 1hr 15min) He mentions a cooker element parallel to the fuse to absorb the voltage peak due to a blown fuse and save the inverter. I figured it was just for LV testing but wasn’t sure about how low/high to use it. Could anyone please let me know what I would need to wire differently for this LV testing setup? I haven’t moved up in voltage yet, that’s why I’m asking before I do. Sorry if that wasn’t clear. I must have misunderstood the use/wiring of the element. I will take it out of the circuit for now. Thanks so much for the help as usual
Edit:also this heating element doesn’t have any voltage on the outside.

[phillipschip]

Could someone please possibly chime in and let me know how to properly wire the stove element for testing, and about what voltage it is no longer useful? Use would be described at about 1:13 in the “how not to kill a Tesla drive unit” video. It sounds like I had it wired wrong and I’m trying to cover all my bases and be as careful as possible. Thanks!

[tom91]

In series with the inverter. (you know basics of electronics right to understand series?)

[barracuda816]

Ok, I am also a little confused here too. I thought the idea of the cooker heater was to be in parallel with the breaker, so in the event of an overcurrent (where the breaker trips) the element will limit the current to the inverter whilst remaining in circuit and therefore not frying the inverter? It also had the benefit of acting as a precharge resistor (by turning on the or connecting the power supply with the breaker off, then breaker on when the voltage has equalised).

If my thinking is not wrong then the OP has wired it up correctly. Obviously the photo shows the low voltage set up, going higher defo wants a bit more safety (cover exposed terminals, correct rating breaker or fuses, and don't put the heater element on a flammable surface as a min)

I may be wrong. But I think we are throwing a bit too much negativity at the OP. This site is a learning resource after all and I for one would hate to see this usually, friendly, helpful resource go the way of say the piston heads forum where everything is immediately met with hostility and negativity.

[johu]

Of course you do have a point.

It's a fine line. People have left the forum because they found there was too little focus on safety and that gross mistakes aren't called out clear enough (or even encouraged, ahem...). The sentence "Next step I would like is to bench test with one of my 200v battery packs" and then the picture of the setup got me nervous and I found it was time to step in. Resolved now, but wasn't obvious from the original post.

Regarding the setup actually both ways don't make a lot of sense. Putting a 100A fuse in series with the cooker means it won't ever blow. Putting it in parallel means you can't manually interrupt plus the value is too large for testing. In his video Damien used an actual breaker I think rated 16 or 25A

So the plea: communicate friendly even when astonished

[tom91]

Okay lets try and break it down.

Why use a cooker/any large resistor element?
1. Limit the current draw when a fault occurs- this increases the likelihood of things surviving
2. Cause a drop in voltage when larger currents are draw - again this aids to the likelihood of things surviving

This is meant as a "did I not mess up" any wiring or settings step. You should always of course double/tripple check your wiring and settings before powering on any circuits. It is also strongly recommended to verify each step of the HV system being activated with actual measurements not just "I heard it click"

Putting a 100A fuse in series with the cooker means it won't ever blow

Exactly, so making sure there is no catastrophic loss of voltage. Then again losing voltage when the motor is spinning underload would only be a catastrophic loss of voltage.

[nkiernan]

To maybe help the discussion, hoping a quick component layout might help. If this is incorrect or will only confuse things, let me know and I can edit or remove. If its helpful, I can add it to the wiki along with any suggested changes?

[tom91]

hoping a quick component layout might help

These are correct. I personally would not recommend the second layout for anything but development work, ensuring the inverter is not set to opening contactors under a fault condition is key in all setups.

Also after removing the element and "deploying" the setup for driving ensure the inverter is configured correctly for not fully dropping out contactors on a fault.

DC breakers expensive when sized right for the job.

[phillipschip]

Thanks for the responses on this. It is this video by Damien that I am referring to:

At 1:12:16 he begins to draw out a diagram of use for the cooker element.
At 1:13:40 he mentions to wire it in "PARALLEL".

In series with the inverter. (you know basics of electronics right to understand series?)

I am learning more and more each day, and having a lot of fun doing it too. I am definitely far from an electrical engineer but thankfully I do know the difference between parallel and series.

The cooker element I have been using for 36v doesn't have any voltage on the outside, and doesn't heat up at all the way I have it wired. I have a 100 amp fuse because I am testing with the motor in the car turning the wheels and my meter is measuring current above 50amps at times. A 25a fuse would be too small for testing like this.

At this point I am just going to keep the cooker element out.

I may be wrong. But I think we are throwing a bit too much negativity at the OP. This site is a learning resource after all and I for one would hate to see this usually, friendly, helpful resource go the way of say the piston heads forum where everything is immediately met with hostility and negativity.

A quick comment on this quote, and thanks for chiming in Funny, I have a 65 Mustang that I have completely re-built. At the start I had little knowledge of the car, and process. There was one main forum (kind of a piston head forum) that pretty much guided me through the entire process with responses to my many questions along the way (vintage-mustang.com), and I can't think of one time that there was any negativity.

[jrbe]

Damien had the cooker element in parallel with the fuse so if the fuse blew there was still a path for the generator energy to go back into the battery. ..so it doesn't blow the inverter.

This leaves a potential short fed through the cooker element. It also leaves high voltage exposed and a potential high heat source as well. Just all things to be aware of and plan for.

You can use a cooker element in series at lower power levels to help "bring up" the system. If there's an issue the heater element will get hot instead of a dead short blowing a fuse or worse.

The high voltage and high heat sources will bring in their own potential dangers. Be aware of what can happen before you start. Not forgetting the high voltage can be tough if the element gets hot. Try not to panic, you have some time to resolve / shut it down.
These heater elements are .7k-5kw typically, so realize if you start putting a bunch of energy into the motor they may start to get hot even when things are ok.

[tom91]

Damien had the cooker element in parallel with the fuse so if the fuse blew there was still a path for the generator energy to go back into the battery. ..so it doesn't blow the inverter.

Damien uses it alot, in both setups as per drawing.