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by coulomb
Tue, 23 Jun 2009, 19:00
Forum: Batteries, charging, management and monitoring
Topic: Sky Energy LiFePO4 Bulk Buy this Week
Replies: 48
Views: 10974

Sky Energy LiFePO4 Bulk Buy this Week

When I posted a few messages back that I found a link between Sky Energy and Aleees cathode material, I was confusing "BlueSky SE" (whatever they are) and Sky Energy's SE cells. Hey, they both have "sky" in the name, and Sky Energy make cells that are a distinctive blue in colour. Plus, he said "Blu...
by coulomb
Tue, 23 Jun 2009, 14:29
Forum: Electric motors and controllers
Topic: Changing an induction motor voltage
Replies: 433
Views: 118467

Changing an induction motor voltage

Put some AC (24V?) across the whole coil and search for the centre using a capacitance coupled wheatstone bridge. You have spread out the wires ? so probe around a bit. May need to use more than 24V or 50Hz. Yes, I was thinking of using RF, but then it will probably all radiate. So maybe higher fre...
by coulomb
Tue, 23 Jun 2009, 14:08
Forum: Batteries, charging, management and monitoring
Topic: Sky Energy LiFePO4 Bulk Buy this Week
Replies: 48
Views: 10974

Sky Energy LiFePO4 Bulk Buy this Week

I don't believe it. I can't find anywhere that Sky Energy (China) or Aleees (Taiwan) claim that Sky Energy is using Alees cathode material. The source of the claims seems to be http://www.forsenusa.com/batteries.html which some people think is not trustworthy. See http://visforvoltage.org/forum/468...
by coulomb
Tue, 23 Jun 2009, 05:12
Forum: Batteries, charging, management and monitoring
Topic: Sky Energy LiFePO4 Bulk Buy this Week
Replies: 48
Views: 10974

Sky Energy LiFePO4 Bulk Buy this Week

I finally found a name for the Sky Energy "magic sauce": Aleees LFP NCO cathode material (nanococrystelline olivine) Edit: See http://www.aleees.com/en/product/LFP-NCO.htm Edit 2: But this is contended; see next 2 posts. Edit 3: Arrgh! I was also confusing Blue Sky and Sky Energy (which make blue co...
by coulomb
Tue, 23 Jun 2009, 03:47
Forum: Electric motors and controllers
Topic: Changing an induction motor voltage
Replies: 433
Views: 118467

Changing an induction motor voltage

Coulomb, I'd be chasing that dark sleeved wire in the very centre of your picture (not the one your arrow points to) and its mate at the other end of the pole coil. You only need to find the three inter 'pole coil' connections to make your emotor 1/2 voltage. If it is a consequential pole motor the...
by coulomb
Mon, 22 Jun 2009, 17:07
Forum: Electric motors and controllers
Topic: Changing an induction motor voltage
Replies: 433
Views: 118467

Changing an induction motor voltage

Or you can get it rewound. Yes, I thought of that... but a rewind (at some $800) plus bearings ($100?) plus balance ($120?) seems out of proportion to its cost so far ($85). Plus, it's cast iron. But it's still a possibility. I'd still prefer to scrounge another motor and rewire it, but the chances...
by coulomb
Mon, 22 Jun 2009, 15:28
Forum: Members Machines
Topic: Weber and Coulomb's MX-5
Replies: 1698
Views: 369689

Weber and Coulomb's MX-5

Tritium_James wrote: Hmmm, looking at that data more closely, the offset request times on the serial port don't explain it. Weird.

It sort of does if the current is sampled first, then the voltage. But then why is the voltage sent first? Maybe they are cached.
by coulomb
Mon, 22 Jun 2009, 04:38
Forum: Electric motors and controllers
Topic: current limiting on Curtis and TS cells
Replies: 74
Views: 9641

current limiting on Curtis and TS cells

For the purists, the Thunder Sky 40 Ah 3C discharge-with-fan graph has had the older (temperature with no fan) data corrected a second time. The data was shifted, and I incorporated some interpolated data from Weber. That horrible deformity near the end of the discharge is now gone. The two graphs s...
by coulomb
Mon, 22 Jun 2009, 01:57
Forum: Members Machines
Topic: Weber and Coulomb's MX-5
Replies: 1698
Views: 369689

Weber and Coulomb's MX-5

Er, coulomb, how about you correct for that in the spreadsheet and update the graph above. It was definitely at 120 A where we saw 0.1 V drop in the cables. Err, Weber, what a good idea. Done. The little overshoots are interesting, e.g. at the beginning of the 4C charge. But I think it's just a sam...
by coulomb
Sun, 21 Jun 2009, 16:56
Forum: Electric motors and controllers
Topic: Changing an induction motor voltage
Replies: 433
Views: 118467

Changing an induction motor voltage

Squiggles wrote: How many slots has that motor got?

It has 36 slots. So 12 slots per phase.
by coulomb
Sun, 21 Jun 2009, 16:33
Forum: Electric motors and controllers
Topic: Changing an induction motor voltage
Replies: 433
Views: 118467

Changing an induction motor voltage

I've been continuing on this motor rewire for sheer don't-know-when-to-quittedness. I've found 2 of the twelve crossovers: http://forums.aeva.asn.au/uploads/689/wiring_mess_sm.jpg The two that I've found were near the inside (towards the rotor) of the slots, so I thought maybe that was the way to fi...
by coulomb
Sun, 21 Jun 2009, 07:13
Forum: Technical and conversion discussion
Topic: Soapbox on regenerative braking
Replies: 278
Views: 33584

Soapbox on regenerative braking

I think around 2003 there was only one AC Tangara in the NSW fleet, and it happens to be the one involved in the Waterfall disaster. They were using all DC, and decided to get one AC as a trial. The hardware was cleared by the enquiry, so it was probably just a big fluke that the only AC train out o...
by coulomb
Sun, 21 Jun 2009, 05:48
Forum: Technical and conversion discussion
Topic: Soapbox on regenerative braking
Replies: 278
Views: 33584

Soapbox on regenerative braking

Heh, interesting. From this document on the same site:       "Historically, DC technology has been the lower initial-cost option for heavy-haul freight applications. However, DC traction motors are found to be susceptible to reliability issues such as moisture, grounding and commutation problems tha...
by coulomb
Sun, 21 Jun 2009, 05:17
Forum: Technical and conversion discussion
Topic: Soapbox on regenerative braking
Replies: 278
Views: 33584

Soapbox on regenerative braking

My understanding is that the classic Diesel Electric locos used the Ward-Leonard set. That's two DC machines with separately excited (!) fields and armatures connected to each other. By adjusting the field currents, it was possible to create a sort of continuously variable transmission. The diesel e...
by coulomb
Sun, 21 Jun 2009, 04:04
Forum: Electric motors and controllers
Topic: Changing an induction motor voltage
Replies: 433
Views: 118467

Changing an induction motor voltage

It seems that not all 4-pole motors (like mine) can be quarter voltaged; they have consequent poles. But some can't even be half voltaged: http://forums.aeva.asn.au/uploads/689/y_oh_y_002_sm.jpg Note the joins: the wires from the junction box split into two (and they all do), so the two poles are in...
by coulomb
Sun, 21 Jun 2009, 03:48
Forum: Members Machines
Topic: Weber and Coulomb's MX-5
Replies: 1698
Views: 369689

Weber and Coulomb's MX-5

Oh, that reminds me: the power supply was not set up with 4-wire Kelvin leads. The leads (as you can see) are quite fat, but there is still about a milliohm of resistance, so the voltage on the cell would have been a little lower than indicated. We measured 3.65 V on a multimeter when the power supp...
by coulomb
Sun, 21 Jun 2009, 03:42
Forum: Technical and conversion discussion
Topic: Soapbox on regenerative braking
Replies: 278
Views: 33584

Soapbox on regenerative braking

I had some musings about regen using series wound brushed DC motors on my White Suzi page.

Unfortunately, I got a bit muddled, and forgot about the reversing the field problem.
by coulomb
Sun, 21 Jun 2009, 02:39
Forum: Members Machines
Topic: Weber and Coulomb's MX-5
Replies: 1698
Views: 369689

Weber and Coulomb's MX-5

Coulomb / Weber, that new lab supply I was telling you about has turned up here (up to 8V, up to 300A, fully programmable) so if you'd like to do some charge testing on these cells... Well, we were certainly happy to take up TJ's generous offer. The cell on the large cables: http://forums.aeva.asn....
by coulomb
Sat, 20 Jun 2009, 15:56
Forum: Technical and conversion discussion
Topic: Soapbox on regenerative braking
Replies: 278
Views: 33584

Soapbox on regenerative braking

Well I think everyone agrees that commutated motors have a limited lifespan and will only be around while they offer a significant cost and/or simplicity advantage. Ok, but I think that DC will be around for a while yet. So I guess those of us involved with EV R&D should be doing our best to bring ...
by coulomb
Sat, 20 Jun 2009, 04:52
Forum: Electric motors and controllers
Topic: Motor Design Parameters
Replies: 5
Views: 1301

Motor Design Parameters

Is there data available that can help determine the maximum frequency a laminated silicone steel core can be switched at? I believe it depends on the thinness of the material. Thin laminations are a pain to work with and use more labour (or robot time) to produce, so they are more expensive. I beli...
by coulomb
Fri, 19 Jun 2009, 20:30
Forum: Electric motors and controllers
Topic: Changing an induction motor voltage
Replies: 433
Views: 118467

Changing an induction motor voltage

1. Heat dissipation. This includes melting winding wires and insulation breakdown through over-temperature. 2. Breakdown torque. 3. Winding insulation breakdown due to absolute voltage difference. 4. Winding insulation breakdown due to voltage rate of change (dV/dt) value. 5. Speed limit (for bearin...
by coulomb
Fri, 19 Jun 2009, 14:09
Forum: Electric motors and controllers
Topic: current limiting on Curtis and TS cells
Replies: 74
Views: 9641

current limiting on Curtis and TS cells

Johny wrote: didn't mean to grill you about the dog.

Oh, no taken that way. All good fun.
by coulomb
Fri, 19 Jun 2009, 06:10
Forum: AEVA ACT Branch
Topic: EV Run to Canberra AGM 2009
Replies: 90
Views: 30419

EV Run to Canberra AGM 2009

I'd love to attend; especially I'd like to take a week off and drive in a lovely red electric MX-5. I don't have a good feel for how likely the MX-5 will be ready by then. If not, I'd be happy to fly down for a few days. Also, I don't know how likely it is that I'll be allowed out for a week; a few ...
by coulomb
Fri, 19 Jun 2009, 05:28
Forum: Electric motors and controllers
Topic: Changing an induction motor voltage
Replies: 433
Views: 118467

Changing an induction motor voltage

We have an unofficial agreement with departments to email around the workshops... Workshops! Ah, they were the days. I used to work for Telecom Workshops at Bulimba, Brisbane, as an electrical engineer class 2. Now the whole workshops are gone - we had numerically controlled punch presses, milling ...
by coulomb
Fri, 19 Jun 2009, 05:13
Forum: Electric motors and controllers
Topic: Changing an induction motor voltage
Replies: 433
Views: 118467

Changing an induction motor voltage

... Or you could just use a 240V to 240V isolating transformer ... Connect to two 'line in' terminals and then the internal inrush system of the VFD (High side phase angle triggered SCR or PTC/Contactor) would all work as normal. No voided warranty. I'm not so sure actually. I have a suspicion that...