NCOP14 regulations, safety and revision

Technical discussion on converting internal combustion to electric
User avatar
acmotor
Senior Member
Posts: 3595
Joined: Thu, 26 Apr 2007, 03:30
Real Name: Tuarn
Location: Perth,Australia

NCOP14 regulations, safety and revision

Post by acmotor » Sat, 31 Jan 2009, 19:38

The centre tap really applies to the overall battery pack, not multiple modules, so don't be concerned there.

The centre tap may be a resistance to chassis that controls the voltage by which the pack may float away from chassis and provides the first circuit path for leakage detection. (the leakage (fault) being the second path) The centre of the battery pack is also the ideal place for pack fusing as it results in the pack being broken ito lower voltage in the case of a fault. (e.g. Prius does this)

Remember here that EV conversions are relatively unique in having parts of the battery pack distributed around the vehicle and not as one 'module'.

Just reading AS3000...
Extra low voltage is defined as "50V AC or 120V ripple free DC" ... There is a 25V AC, 60V ripple free DC cut off for non insulated circuit construcion in the standard in dry areas and 6V AC, 15V DC in all other areas. ( don't mention wet engine bays !)
But hey, these are numbers and there are still "area of potential contact" issues involved.

SELV and PELV (separated and protected extra low voltage) are accepted methods for "protection for safety" however the ELV voltage limits above apply otherwise the game changes to LV.
Once you enter LV then full insulation and barriers etc must be used and there must be bonding of all "accessible conductive parts" e.g. motor, controller body and vehicle body etc. so a fault cannot make them live with respect to each other.
This is still considered a separated circuit isolated from a protective ground. A common technique in EVs.

But AS3000 continues... "Separated LV circuits shall not exceed 500V"
LV being under 1000V AC or 1500V DC
This applies to red suzi with 576V (nominal) batteries where voltage can rise to 750V.
AS3000 requires that I do NOT use an isolated (edit: separated circuit)battery pack.
Note. Motor manufacturer and controller manufacturer also require the centre of the supply to be neutral/ground (chassis in the case of my EV)


The test requirement for PELV and SELV is "500V AC for 1 min."
At what point does the EV fraternity choose the comply or not comply with AS3000 ?

This may all seem complex but is quite logical for safety.

I think it was Rob who suggested we need an "EV applicable" extraction from AS3000. Image
Last edited by acmotor on Sat, 31 Jan 2009, 10:00, edited 1 time in total.
iMiEV MY12     105,131km in pure Electric and loving it !

User avatar
woody
Senior Member
Posts: 1713
Joined: Sat, 21 Jun 2008, 02:03
Real Name: Anthony Wood
Location: Mt Colah

NCOP14 regulations, safety and revision

Post by woody » Sat, 31 Jan 2009, 20:27

coulomb wrote:
woody wrote: easy. 144V pack is actually +/- 72 Volts if you ground the centre via a relay or ...
Suppose you have a 576v nominal system made up of four 144v modules. I don't believe that any manufacturers of 144v modules do/would provide a "centre tap" for this. I don't want to void the warranty of my modules by opening them and providing such a centre tap. Besides, they will probably be safer unopened, with the manufacturer's original seals for water tightness, etc.
I think they would provide the feature if it was clear to them that they couldn't make any sales without it :-)

acmotor, your summary of AS3000 is great.
Planned EV: '63 Cortina using AC and LiFePO4 Battery Pack

HeadsUp
Groupie
Posts: 265
Joined: Sat, 28 Feb 2009, 09:13
Real Name: Mark W
Location: Sydney

NCOP14 regulations, safety and revision

Post by HeadsUp » Sun, 01 Mar 2009, 06:52

i didnt have 3 hours to read all three pages of posts in this thread , so... forgive me if this has been mentioned already

Regarding electrical safety

the field winding of the motor will probably also need to be isolated at the motor to prevent a towed vehicle from becoming a generator , so include a breaker at that location

love the stuff i read already , you guys are doing great work .

good luck all.

User avatar
Richo
Senior Member
Posts: 3650
Joined: Mon, 16 Jun 2008, 00:19
Real Name: Richard
Location: Perth, WA

NCOP14 regulations, safety and revision

Post by Richo » Sun, 01 Mar 2009, 08:26

AC won't matter as the bridge is shut down so no EMF is created.
DC you normally have contactors on the motor to change directions.
So when off the contactors are open so a properly wired motor shouldn't ever become a generator.
Help prevent road rage - get outta my way! Blasphemy is a swear word. Magnetic North is a south Pole.

User avatar
acmotor
Senior Member
Posts: 3595
Joined: Thu, 26 Apr 2007, 03:30
Real Name: Tuarn
Location: Perth,Australia

NCOP14 regulations, safety and revision

Post by acmotor » Sun, 01 Mar 2009, 18:13

BLDC or other permanent magnet type motors may present issues though ?
There are usually no contactors involved. (We won't always be using series DC !)

BLDC servos I have worked on warn not to rotate the motor with the controller unpowered as the generation of power can cause damage to the controller circuitry. A short in the controller output stage can cause considerable braking at the motor. I've tried that !!

I guess HeadsUp is thinking direct drive ? And this probably covers hub motors as well. Fortunately, manufacturers of commercial EVs in the future will issue the appropriate warnings.

It may be a "do not tow" without lifting drive wheels situation as per many automatics. This may be a smart move in any case so HeadsUp's HeadsUp is probably a good one that should be in EV guidelines. Image
iMiEV MY12     105,131km in pure Electric and loving it !

bga
Senior Member
Posts: 492
Joined: Mon, 01 Sep 2008, 19:27
Real Name: Bruce Armstrong
Location: Perth WA

NCOP14 regulations, safety and revision

Post by bga » Sun, 01 Mar 2009, 21:17

Because there is virtually no chance of constructing an EV the meets the requirements for 'double insulated' that is used in common non-earthered appliances, it should not be considered possible to make the electrical systems in any way 'safe' by floating them.

This decision is made for other reasons.

Factors may include:
Is there a possibility for substantial leakage currents during normal operation, sich as through a DC series motor.
Is it desired to measure the magnitide of a fault current so that an operational decision can be made.

An EV is different to a hair fryer, the consequences of an RCD trip may be much greater if it results in the vehicle becoming needlessly disabled in a really bad place on the road.

My conclusion after considerable thought:
DC Series systems, floating is a good option. (I think that my motor leakage theory offers a valid guide as to why this is common in DC systems)
AC systems, grounded with current monitoring. (For most systems, this most closely analogs the installed configuration of the industrial application)

Mandating any solution is not necessary.
This should be a system design issue.

The AEVA may offer guidance so that constructors can have confidence that they are making a sound decision.


HeadsUp
Groupie
Posts: 265
Joined: Sat, 28 Feb 2009, 09:13
Real Name: Mark W
Location: Sydney

NCOP14 regulations, safety and revision

Post by HeadsUp » Mon, 02 Mar 2009, 00:02

i think it should be in the checklist for EV builders , whatever drive system they use , builders and authorities have to understand the need for protection systems

if it requires isolation to prevent power generation under tow , then the guidelines must specify as such

it is not necesarily applicable to only direct drive systems , if its a manual gearbox transmission the vehicle would probably be in gear while parked and your friendly towtruck driver cant be trusted to know the difference , although they usually break in to the car to release the handbrake and put a car in neutral , it could also be a front wheel drive car but the towie tows it by the rear wheels , who knows.

if there is an accident , or a vehicle is towed away from a parking zone by a tow truck , you can never rely on murphys law to not raise his ugly head.

( apologies to any descendants of the aforementioned Mr Murphy )

imagine a case where an accident causes the cables between motor and contactor to be crushed against the motor casing , if towed that way you have voltage potential looking for a home.

in most cases a vehicle will be placed in neutral before towing but we have to include human behavioural dynamics into engineering analysis

it could result in a burnt out controller , damaged motor , fire or electrocution .

So , lets just dot our I's and cross our T's , include it on the guideline checklist.

thankyou muchly.
Last edited by HeadsUp on Sun, 01 Mar 2009, 13:12, edited 1 time in total.

Sparky Brother
Groupie
Posts: 95
Joined: Sun, 30 Mar 2008, 05:20
Real Name: Angel T.
Location: Melbourne

NCOP14 regulations, safety and revision

Post by Sparky Brother » Mon, 02 Mar 2009, 03:11

Hey HeadsUp

I wouldn`t like to be the person to discourage you from the Safe wise thinking but that last part with the cables crushed betbeen the motor and car`s body with the car meanwhile being towed generating deadly voltage sounds like a one in a million case to me. Secondly in order some one to get electric shock wouldn`t they be in a funny situation where they are running alongside the towed vehicle trying to touch simultaneously the plus and minus cables of the car or may be the body and the ground and eaven in that case I`m not sure there will be difference in the potentials to make the bad thing happen.

I hope my point is somewhat valid. In case I did not quite get it - apologies for that.



User avatar
Richo
Senior Member
Posts: 3650
Joined: Mon, 16 Jun 2008, 00:19
Real Name: Richard
Location: Perth, WA

NCOP14 regulations, safety and revision

Post by Richo » Mon, 02 Mar 2009, 10:09

acmotor wrote:this probably covers hub motors as well.
Fortunately, manufacturers of commercial EVs in the future will issue the appropriate warnings.


Really?
We could ask the manufacturers of the mini with 4 hub motors what they did.
"Sticker on window fixed it: explodes when towed" Image
Image

Maybe we should just specify all eVs use AC induction motors for safety reasons Image

Still a vaild point.
Even looking at if from controller design I don't see an easy practical way around it.
You can't account for every situation esp in an accident when the electrics become compromised.

The workable solution is:
1. ensure the car is OFF.
2. 2WD tow from the drive wheels.
3. 4WD/AWD/4HUB must be towed on trailer.

Assuming that a BLDC eV is being towed the wrong way ie with drive wheels on the ground.
If the controller is not powered or damaged then:
1. The back emf created is rectified onto the DC bus rails via the flyback diodes.
2. The DC bus rails shouldn't go anywhere as the car is switched off and the battery pack is isolated.
3. If the car is still in first then the voltage could be higher than expected as the RPM could be 2-3x the nominal RPM limit. (This could be a problem)
Help prevent road rage - get outta my way! Blasphemy is a swear word. Magnetic North is a south Pole.

Sparky Brother
Groupie
Posts: 95
Joined: Sun, 30 Mar 2008, 05:20
Real Name: Angel T.
Location: Melbourne

NCOP14 regulations, safety and revision

Post by Sparky Brother » Mon, 02 Mar 2009, 17:44

OK. Check tis out. In a really bad situation where the car is so crushed so the wiring became compromised I personally wouldn`t even think of towing it away on the back, front wheels. Most cars nowadays are towed on a trailer anyway and from this point of view there was enough good discussion on the protective cirquitry on this thread that provides enough safety by disconnection and braking into save voltages main pack and a contactor to brake the motor-controller connection and the big red mushroom head button inside the car most of us agreed upon with, the simple sign saying "Electric Car" should ring the bell for the Tow truck driver that the car is to be towed on a platform ONLY.

And yes. As a simple precaution to a motor becoming a generator, how hard can it be for the designer to implement a mechanical blocking device such every car with an auto transmission have (the P position of the gear stick) that provides the required feature i.e. not to make the rotation of the rotor of the motor possible?



User avatar
Johny
Senior Member
Posts: 3729
Joined: Mon, 23 Jun 2008, 16:26
Real Name: John Wright
Location: Melbourne
Contact:

NCOP14 regulations, safety and revision

Post by Johny » Mon, 02 Mar 2009, 17:55

spary_bother "how hard can it be for the designer to implement a mechanical blocking device".

That could get very expensive sparky. The Mitsubishi Miev is a case in point. With wheel motors (I'm assuming they are brushless DC with permanent magnets) the towies have their first car that they really must use a tray towtruck.
With all the AWDs around nowadays, a tray really is the only viable towing method anyway.

Sparky Brother
Groupie
Posts: 95
Joined: Sun, 30 Mar 2008, 05:20
Real Name: Angel T.
Location: Melbourne

NCOP14 regulations, safety and revision

Post by Sparky Brother » Mon, 02 Mar 2009, 18:14

Hi John. The mechanical blocking device is something I`ve been thinking froim the very beginning so this is something I will try to implement into my conversion as a safety feature since my car will be a direct drive, therefore there will be nothing else to immobilise it on a slope but the hand brake which I deem not that secure for number of reasons.

As to the cost of such a protective device and could something readily available be used I must admit I have no Idea but that is certainly something to figure out ASAP.


Last edited by Sparky Brother on Mon, 02 Mar 2009, 07:31, edited 1 time in total.

User avatar
woody
Senior Member
Posts: 1713
Joined: Sat, 21 Jun 2008, 02:03
Real Name: Anthony Wood
Location: Mt Colah

NCOP14 regulations, safety and revision

Post by woody » Mon, 02 Mar 2009, 18:31

Initially my thoughts for this were along the lines of a parking pawl (similar to Park Brake) which engaged with the cog used for rpm measurement.

Since a4x4kiwi's cog seems to have too few teeth for speed monitoring, one ring-gear to rule them all seems a bit of a stretch.
Planned EV: '63 Cortina using AC and LiFePO4 Battery Pack

User avatar
Johny
Senior Member
Posts: 3729
Joined: Mon, 23 Jun 2008, 16:26
Real Name: John Wright
Location: Melbourne
Contact:

NCOP14 regulations, safety and revision

Post by Johny » Mon, 02 Mar 2009, 18:32

Sorry sparky, I misunderstood. I misread your post to be talking about isolating the motor from the wheels when really you meant something like an auto-trans parking pawl. I get it now.

Yes it would be good and I wonder if taking a4x4kiwi's toothed coupling and using the teeth not only to run the inductive pick-up but also having spring loaded tongue locking system when in "Park". Spring load designed to hold on steep hills but but make a terrible noise and not lock up the wheels if applied at speed - again similar to auto transmission lock - (is this needed?).

User avatar
Johny
Senior Member
Posts: 3729
Joined: Mon, 23 Jun 2008, 16:26
Real Name: John Wright
Location: Melbourne
Contact:

NCOP14 regulations, safety and revision

Post by Johny » Mon, 02 Mar 2009, 18:35

Hey woody you copied me - in advance???

User avatar
woody
Senior Member
Posts: 1713
Joined: Sat, 21 Jun 2008, 02:03
Real Name: Anthony Wood
Location: Mt Colah

NCOP14 regulations, safety and revision

Post by woody » Mon, 02 Mar 2009, 18:36

Snap!

I think it's needed. Automatics have "Park". Manuals have "Leave it in gear". DD EV's have "Turn the wheels when you park" or "Carry a brick".
Planned EV: '63 Cortina using AC and LiFePO4 Battery Pack

Sparky Brother
Groupie
Posts: 95
Joined: Sun, 30 Mar 2008, 05:20
Real Name: Angel T.
Location: Melbourne

NCOP14 regulations, safety and revision

Post by Sparky Brother » Mon, 02 Mar 2009, 18:42

"DD EV's have "Turn the wheels when you park" or "Carry a brick"." Image

I love that last one Woody!

John. I recon the Grrr noise is easily avoidable by some sort of interlock I.e. Ignition- ON solenoid ON too. No chance to make the cog singing

User avatar
woody
Senior Member
Posts: 1713
Joined: Sat, 21 Jun 2008, 02:03
Real Name: Anthony Wood
Location: Mt Colah

NCOP14 regulations, safety and revision

Post by woody » Mon, 02 Mar 2009, 18:43

Johny wrote: Hey woody you copied me - in advance???
Great fools never think alike :-)
Planned EV: '63 Cortina using AC and LiFePO4 Battery Pack

HeadsUp
Groupie
Posts: 265
Joined: Sat, 28 Feb 2009, 09:13
Real Name: Mark W
Location: Sydney

NCOP14 regulations, safety and revision

Post by HeadsUp » Mon, 02 Mar 2009, 19:45

hey guys , with respect to design of a " toothed locking pawl or cog "

you want to consider that if its an ignition key on- power on- cog disengaged scenario , what happens if you lose electrical power for any reason while driving , or you accelerate hard and the drive motor sucks all the power , causing the solenoid operated pawl to lose power and engage the cog .

no stereo system required then to hear heavy metal music

IF you did design a pawl or cog type lock , it is possible that the system could lock up when parked on a slope , so it would have to be designed to eliminate friction from side loading

i am leaning a little more towards a disc brake style parking brake on the drive shaft as close to the diff as possible


User avatar
woody
Senior Member
Posts: 1713
Joined: Sat, 21 Jun 2008, 02:03
Real Name: Anthony Wood
Location: Mt Colah

NCOP14 regulations, safety and revision

Post by woody » Mon, 02 Mar 2009, 20:04

They mostly stopped using disc brakes for parking brakes a while ago (they slip because it's hard to get the force required without a booster). Most rear-wheel disk cars now have a little drum brake in the hub which does the handbrake.

Old land rovers had a drum brake on the tailshaft.

Wikipedia mentions late model Audis etc. have electrically operated handbrakes.
Planned EV: '63 Cortina using AC and LiFePO4 Battery Pack

Sparky Brother
Groupie
Posts: 95
Joined: Sun, 30 Mar 2008, 05:20
Real Name: Angel T.
Location: Melbourne

NCOP14 regulations, safety and revision

Post by Sparky Brother » Mon, 02 Mar 2009, 20:29

Yeah. Didn`t come up with the power loss issue Image. How about gear stick in P position - control cirquit open-controller disabled ?

HeadsUp
Groupie
Posts: 265
Joined: Sat, 28 Feb 2009, 09:13
Real Name: Mark W
Location: Sydney

NCOP14 regulations, safety and revision

Post by HeadsUp » Mon, 02 Mar 2009, 20:30

i was thinking of a disc brake which has a spring applying force while at rest like a maxi brake on a semi trailer however they use air pressure to release them

we dont want an additional power system ( air compressor ) to release the park brake , so maybe the brake vacuum pump sucking a diaphram releases the park brake , then a locking pin keeps the park brake disengaged until required , so the park brake does not constantly load up the vacuum pump .

or just an old fashioned hand brake lever which disengages the disc brake to keep it simple , ( acting in reverse )

you can still use the park brake for doing " hill starts " , whereas i think the locking pawl or cog type would give you problems in that area

i think the reason drum brakes are used as parking brakes is the diameter.
a wide ,small diameter drum brake can be used for parking , whereas a disc brake would hang too low and interfere with the ground clearance
under the car.

the posts above were looking for a secondary lock alongside a traditional OEM handbrake .

to be honest i dont think i have a satisfactory proposal yet that is foolproof , so i will keep looking , at least with all of us throwing ideas at the ceiling , eventually we will find something that sticks.

cheers


ps , should we put the handbrake / parking lock stuff into a seperate post so the NCOP post is not cluttered up too much ?
Last edited by HeadsUp on Mon, 02 Mar 2009, 09:40, edited 1 time in total.

fuzzy-hair-man
Groupie
Posts: 118
Joined: Wed, 12 Nov 2008, 16:40
Location: Canberra

NCOP14 regulations, safety and revision

Post by fuzzy-hair-man » Mon, 02 Mar 2009, 22:04

HeadsUp wrote: i think the reason drum brakes are used as parking brakes is the diameter.
a wide ,small diameter drum brake can be used for parking , whereas a disc brake would hang too low and interfere with the ground clearance
under the car.
I think Woody is right, if you look at the rear brakes on most / any car that has 4 wheel discs the rear disks have a small drum brake in the centre, if they were able to use the disk easily or cheaply why would they then add the drum to the centre? these drums are only used for the hand brake, and again Woody is right disks require higher pressures than drum brakes hence brake/vacumn boosters on disk brake cars. I think there's also the factor that the handbrake needs to be completely separate from the hydraulic brakes so the hand brake is operated by cables and mechanically so if the hydraulic brakes were damaged or didn't work the hand brake is available in an emergency, not that I'd like to slow quickly from 100km using just the handbrake. Image

User avatar
Richo
Senior Member
Posts: 3650
Joined: Mon, 16 Jun 2008, 00:19
Real Name: Richard
Location: Perth, WA

NCOP14 regulations, safety and revision

Post by Richo » Mon, 02 Mar 2009, 22:34

If you are going direct drive use the old clutch on the non-drive end of the motor where one side of the clutch is fixed.
Just reverse the cable so it is engaging the clutch when pressed.

Help prevent road rage - get outta my way! Blasphemy is a swear word. Magnetic North is a south Pole.

User avatar
carnut1100
Groupie
Posts: 334
Joined: Tue, 24 Feb 2009, 16:39
Real Name: Greg Milligan
Location: Brisbane
Contact:

NCOP14 regulations, safety and revision

Post by carnut1100 » Tue, 03 Mar 2009, 17:04

Using a Park pawl from an old autobox would be fine. Just cable operate from an auto shifter. Put it in P and it is locked.

Post Reply