Paul and Sabrina's Cheap 3 Phase Inverter (AC Controller) with Field Oriented Control

[motorulf]

Originally Posted by kalidasbala

Btw, is there a formula to calculate the precharge resistor value? Also can I use an automotive relay (12v).

The precharge resistor value is a function of capacitance, time and voltage.
I dont have a formula though. Or... i found this
Use a relay that can handle the voltage. I dont think a 12v relay will do the job

Originally Posted by kalidasbala

You are using 25v as HV and running a 208Vac 3PH motor? What kind of batteries are you using?

I was using a:

Then i used 3 in series, making it 75 volts.
I use them only for testing, for my convenience...

[MPaulHolmes]

oh yes! precharge resistor/capacitance/time. You need to figure out the RC time constant for your setup. Like this:

Let's say you are using 1000uF of bus capacitance, and you are using a precharge resistor that is 500 Ohms (just random values). Also, let's say you are using 400v for your battery bank.
Things to consider:

1. The precharge relay will have to be able to make 400v/500Ohm = 0.8 amps.

2. The time you need to wait is 5*R*C seconds. So,
5*500Ohm * 0.001Farad = 2.5 seconds. (0.001 Farad = 1000 microfarad)

3. The energy that your precharge resistor must be rated for is:
Energy = 0.5 * C * V * V = 0.5 * 0.001Farad * 400v * 400v = 80 Joules

That's a lot of energy for a resistor. You need a pulse handling resistor like the king of surge resistors, the Ohmite pulsEater (I love that name!):
http://www.mouser.com/ProductDetail/...0Td1E32eWcg%3d

That can handle way more than 80 Joules, so it would be very safe. If a resistor doesn't list its pulse rating in Joules, I would say you should probably not use it.

[thingstodo]

Originally Posted by arber333

I have 60 holes single pulse optical encoder allready on my car.
Encoder is this HC-020K Double Speed Measuring Module With Speed Encoder Kit | eBay
It is powered by 5V and signal is open collector pulse. Would it work with only channel A?

I have a small bit of information for this:

Open collector works fine - the pull-up resistor needs to be sized to allow the voltage to rise to 4.5V before it is 'pulled down' by the open collector. That's my experience using a 24V encoder, separately powered from the inverter. My other motor has a 64 ppr encoder so 60 pulses per revolution should be OK.

I lost a wire, either A or B channel, while the motor was operating and the inverter got quite confused. It ended up stopping but the deceleration was not smooth.

If you only have one channel, the inverter will not be able to tell which direction the motor is turning. I think Paul is paying attention to that now, for the regenerative braking. But it may not be a big change to disable the direction monitoring?

[MPaulHolmes]

The quadrature encoder interface requires A and B. I had done a virtual high resolution encoder using a single pulse from a tesla using the change notification pin, but Tesla's resolution is only like 36 ticks I think. The problem with 60 might be the high frequency that the change notification interrupt gets called as the motor frequency gets high. I'll have to look at that and see if it's practical.

[MPaulHolmes]

The software changes for getting the change notification pin to generate a virtual high resolution encoder are fairly significant, so it might mean having a separate file for that.

[Turbinepowered]

I literally just joined this forum to say how incredibly delightful this thread has been so far.

I found it two days ago. I'm on page 115 and reading every. single. post.

It's forcing me to remember my 3-phase EE coursework and for that I thank you all.

[shaggythegangsta]

Hello Guys, where i can get the latest schematics and code of Ac controller?
Thanks in advance guys

[thingstodo]

Originally Posted by shaggythegangsta

Hello Guys, where i can get the latest schematics and code of Ac controller?
Thanks in advance guys

Wehzeh - can you confirm that this is the correct github reference? It was the only one that I could find.

https://github.com/MPaulHolmes/AC-Controller

I could not locate your wiki. My skills are not good at searching the forums

[thingstodo]

Paul - can you edit the first post in the thread to point to the github repository and the wiki, or do we need to beg one of the moderators to do that?

[shaggythegangsta]

Originally Posted by thingstodo

Wehzeh - can you confirm that this is the correct github reference? It was the only one that I could find.

https://github.com/MPaulHolmes/AC-Controller

I could not locate your wiki. My skills are not good at searching the forums

Thanks sir, i found that also on web but seems to be old or not?
and there is are no hardware (schematics) files...

it will be very helpful to have latest files on first post