Mesuge wrote: ... are you still after the following spec. for your desired VFD (EValbum): "Control Techniques, Likely 75/90 kW SK5402" ?
I've found some dealer's pricing on them, and it looks quite *attractive < £2,500 for a new drive in the area of 30-45kW nominal rating (RedSuzi&Mal comparison)
Well found, Mesuge. We are determined to make an electric MX-5 with better performance than the original (at least for short sprints) and so we need to go to a frame size 5 (the first digit of the part number) in the Control Techniques drives. And the same company has them too. http://www.inverterdrive.com/catalogue.aspx?search=sk5
But in fact we now think we need the SP5402 "Unidrive" model instead of the SK5402 "Commander" model. Why?
We are planning to use a Control Techniques drive because we have local expertise in using one in an EV. Ross Pink of Electronic Innovations
used one in a Lite Ace van about 3 years ago and what he found good was that you can get a plug in module, called an "Application" module with an additional microprocessor and the ability to write your own software to control the drive at a very low level. You can use this to do clever things to make your AC EV drive like an ICE, so new drivers feel immediately at home.
This is not merely a marketing thing. It is a safety thing. This mostly relates to accelerator and brake response but possibly also battery protection. Neither pure torque control nor pure speed control feel natural to someone used to ICEs, and then there's the whole regen braking thing. You definitely need to be able to flip a switch to go to minimal accelerator-back-off regen when you let a new driver drive your AC EV.
It seems that "Application" modules are only available for the Unidrive (SP) models, not the Commander (SK) models. I'm guessing this means the SPs are more expensive. They do not appear on the above website.
We also think we need the largest frame 5 drive. Why?
It's important to understand those ratings with the two kW numbers e.g. 75/90 kW. They are typical mechanical motor power ratings respectively for "heavy duty" and "normal duty". Yes the lower number is the "heavy duty" number. That's because both numbers are continuous
ratings. The heavy duty continuous rating allows for
a 150% overload for some seconds (maybe a minute if the drive is cold) and the normal duty continuous rating only allows for a 110% overload.
Note that 150% of 75 kW is 112.5 kW and 110% of 90 kW is only 99 kW. i.e. because your continuous operation is at a lower power, and therefore the drive is running cooler, it can hadle a higher power burst.
What we want for EVs is the "super heavy duty" rating that allows for a 500% overload when coming from an even lower base. e.g. Maybe if you were coming from a base of 25 kW you could have a brief burst of 125 kW. But they don't have such a rating. They just tell you you can maintain the 112.5 kW for longer if you're coming from a base of zero (i.e. cold).
The original 1.6 L ICE is 85 kW peak, while the 1.8 L ICE is 98 kW peak. The 2009 model 2.0 L is 118 kW. The smaller frame-5 VF drive is 55/75 kW. 150% of 55 kW is 82.5 kW, hence we need the larger 75/90 kW VF drive with its 112.5 kW peak. It doesn't weigh any more or take up any more space, both of which are unfortunately considerable. 55 kg, 820 x 310 x 310 mm.
Although we may well be limited by the batteries, to a lower power, we want to be ready for future better batteries.
My take on ultracaps is that they are pointless unless they are cheap enough and have a high enough voltage rating to just bolt one in parallel with every battery cell. If you have to have separate balancing and DC-DC converters for them, forget it.
One of the fathers of MeXy the electric MX-5, along with Coulomb and Newton (Jeff Owen).