SalvageS10 Build Thread

[thingstodo]

Another hour. DC output of the DC to AC inverter is 154.7V. The NiCd battery string is at 107.8V. That's a bit of jump, to 1.52V per cell. The current is still about 2.9A, so my toaster must be increasing it's resistance? There is 154.7 - 107.8 = 46.9V across the resistor now. At 2.9A, that works out to a resistance of 16.2 ohms. That is hard for me to explain - no change in current or other conditions but a change in resistance - but I observed it.

Just before the charger is disconnected. DC into the DC to AC inverter, 35.2A at 13.7V. Output of the inverter is 2.8A. This is measured with a clampon meter. It measured 2.9A on the negative and -2.7 on the positive ... so I guess the real value is 2.8A. The voltage is 154.6V. The battery string is at 107.7V.

15 minutes later (after putting things away in the garage) the battery string is at 101.1V standing voltage. This is higher than I was expecting. It is 1.42V per cell. I guess I should check later.

[hamsterpower]

You probably already saw this but the guys over on The Australian Electric Vehicle Association Forums The Australian Electric Vehicle Asn - Powered by Web Wiz Forums™
have done some amazing things with VFDs and small AC motors.

They are driving small SUVs with 14 HP rated AC motors, direct drive, with GOOD performance. Your 40 HP motor may be way big when overpowered with a bigger VFD.

[thingstodo]

Originally Posted by hamsterpower

You probably already saw this but the guys over on The Australian Electric Vehicle Association Forums The Australian Electric Vehicle Asn - Powered by Web Wiz Forums™
have done some amazing things with VFDs and small AC motors.

They are driving small SUVs with 14 HP rated AC motors, direct drive, with GOOD performance. Your 40 HP motor may be way big when overpowered with a bigger VFD.

I have not looked on that group for a while now ... things have changed! Do you remember any specific threads that had some data?

[hamsterpower]

I have not read there in a while either, but if I remember correctly it started in this- Changing an induction motor voltage - The Australian Electric Vehicle Asn - Page 1

and lead to others. Basically take a ~14HP three phase induction motor and a VFD rated more than double that. Lie to the VFD and it was able to (again if I remember correctly) to boost to hundreds of HP and lots of torque. At least for enough time to accelerate a car well.

[thingstodo]

Originally Posted by hamsterpower

I have not read there in a while either, but if I remember correctly it started in this- Changing an induction motor voltage - The Australian Electric Vehicle Asn - Page 1

If anyone is interested, the linked thread is definitely worth a read. They get into a whole lot of theory .. and it looks like it should work ... there seems to be a requirement for the coils in the motor stator to be in series, and joined by an easily-identified 'link'

So I think I'll take apart the 3 motors that I have that are 5 HP as well as the one that is 40 HP and see if the coils ARE in series, and ARE easy to identify.

The thread has not been updated in a while, but I'll cross-post results if:
- my motors are suitable
- I can get the coils separated
- the extra wires fit through the grommet into the motor junction box

The VFD that I'm using for testing will put out 33A, which is 4 times the rated current of the 5 HP motors. That should be enough for me to verify their data ... splitting the phases into separate coils allows for good starting torque and MUCH higher speeds (and much higher power at the higher speeds), but the VFD needs to be oversized.

Some of the experiments they have documented in that thread were a bit scary - running rotors WAY WAY over 'rated' speed ...

If the motors can be modified, I can still run them 'normally' by wiring the 'separated coils' back in series as they originally were, within the motor junction box, so the mod can be 'left in' even if my tests don't work out.

This will be interesting ....

[Ken Fry]

I have likely confused many people about what I'm trying to do. I know that I use a lot of acronyms and that makes it harder to follow. So I'm going to step through the parts and pieces that I have collected and try to explain what my goal is.

I've been following this thread and have been really impressed by your efforts and your great documentation. I appreciate your ingenuity and willingness to share.

[thingstodo]

Sometimes it's embarrassing how focused I get.

... 'I need charged batteries to test' ...

until my wife asks me why I don't just 'plug in' the VFD. It's 208V, and that's 'close enough' to 240V isn't is?

Yes Dear, it is in fact WHY (some time ago) I CHOSE to use 208V for the test VFD. I had forgotten about that. I guess the charging of the batteries at all was a diversion from the goal of testing the 5 HP motor with my newer (well, newer to me) Square D VFD.

33A max output from the VFD, at an estimated output voltage of 50V, with a few factors thrown in and an unknown efficiency is still well under the 30A at 240V single phase rating for the diodes on the input section of the VFD. I likely don't need much more than 2000 watts, maybe 10 amps at 220V.

So I can forget about the batteries again (for a while)
and the charging problems
and the DC to AC inverter soldering
and focus on
1 - take apart a motor and see if the coils are easy to separate
2 - build my test frame again to check the stall torque of the 5 HP motor (likely one that I don't take apart)

A BIG THANK YOU to my lovely wife for the tip. And I always thought she was just smiling and nodding when I talked about my projects ...

[thingstodo]

Originally Posted by Ken Fry

I've been following this thread and have been really impressed by your efforts and your great documentation. I appreciate your ingenuity and willingness to share.

Thanks for the encouragement.

I hope that some of this information will help others get into a project, or help them through some of the issues

[thingstodo]

Originally Posted by hamsterpower

I have not read there in a while either, but if I remember correctly it started in this- Changing an induction motor voltage - The Australian Electric Vehicle Asn - Page 1

Thanks for the link.

I think that a group of people - like a forum - comes up with better solutions than any one person could. Because different ideas are posted, others read them and modify them in some way, and problems are solved!

That sounds kind of corny - I should re-word that somehow - but I think it gets the point across.

[thingstodo]

Originally Posted by thingstodo

...15 minutes later (after putting things away in the garage) the battery string is at 101.1V standing voltage. This is higher than I was expecting. It is 1.42V per cell. I guess I should check later.

Well, I forgot to check the voltage that day. I checked today and the battery string is sitting at 98.1 VDC, and the battery string is outside at -19C or just below 0 fahrenheit ... maybe 1 below. I expect that the voltage would drop quite quickly if I put a load on it.