TMS320F28069F: inverter for ACIMs : implementation of the high-side short current protection function

Jeongsoo Yoo

Hello,

We are developing an inverter for ACIMs by using the InstaSPIN-FOC solution.

With respect to the phase current measurement, we are employing the three-shunt current measurement technique at the low side.

We need some guidance with respect to the implementation of the high-side short current protection function.

Two functions for the high-side short current protection are as follows:

1. Short current protection when one phase of the inverter outputs has been shorted to the earth ground level.

2. Short current protection when two phases of the inverter outputs have been shorted out each other.

Thank you for your guidance.

With regards,

JS Yoo

over 6 years ago

0 Ramesh Ramamoorthy over 6 years ago

TI__Mastermind 27240 points

A simple solution will be to monitor the dc link current as it takes care of all these possibilities.

0 Jeongsoo Yoo over 6 years ago in reply to Ramesh Ramamoorthy

Expert 1025 points

Hi Ramesh,

Thank you for your response.

Would you please provide us some reference designs?

With regards,

JS Yoo

0 Ramesh Ramamoorthy over 6 years ago in reply to Jeongsoo Yoo

TI__Mastermind 27240 points

No, we dont have one. The idea is simple enough, you should be able to do it.

0 Jeongsoo Yoo over 6 years ago in reply to Ramesh Ramamoorthy

Expert 1025 points

Hi Ramesh,

I suppose that the most critical factor may the response time of the protection circuit.

The overall response time of the protection circuit may have to be short enough to protect the IGBT devices.

The protection circuit may have to disable the gates of the IGBT devices at the moment that short circuit current arises.

The response time of the current sensor to monitor the dc link current may also be crucial.

Would you please recommend us some TI devices for this mission?

Thank you for your guidance.

With regards,

JS Yoo

0 Ramesh Ramamoorthy over 6 years ago in reply to Jeongsoo Yoo

TI__Mastermind 27240 points

You are right about the latency of current sensing and protection. Delayed protection signal is of no use.

I will try to see if others can chime in to give the latest answer for you.

0 Javier Contreras4 over 6 years ago in reply to Ramesh Ramamoorthy

TI__Mastermind 34810 points

Hello JS Yoo,

I have a few questions before I give you my recommendations.

For the high side what is the highest Common mode voltage expected. What is the maximum delay time that is acceptable?

0 Jeongsoo Yoo over 6 years ago in reply to Javier Contreras4

Expert 1025 points

Hello Javier,

Thank you for your response.

The highest Common mode voltage for the high side is expected to be not more than 800VDC.

The maximum delay time need to be as short as possible.

We will be pleased if we can have an opportunity to evaluate your recommendations.

Thank you for your guidance.

With regards,

JS Yoo

0 Javier Contreras4 over 6 years ago in reply to Jeongsoo Yoo

TI__Mastermind 34810 points

Hello JS Yoo,

When dealing with this high voltage there are a couple of ways to deal with it. One is using a magnetic approach which sometime requires knowledge in that area to apply it and sometimes is design intensive. The other is to create a supply on the high side and use a digital Current sense amplifier and then isolate the digital communication down to the level you would like. Another option is using a Isolated device like the AMC130x family. Each of these will have there own tradeoffs.

Magnetic- Voltage independent but requires design efforts

Digital CSA - Requires power supply at voltages close to the high common mode and requires a digital isolator. like ISO78xx. Digital delay

AMC130x- Still need to provide a high common mode supply. I do not know all the downsides but we can get an expert on this if this is the path

0 Jeongsoo Yoo over 6 years ago in reply to Javier Contreras4

Expert 1025 points

Hello Javier,

I appreciate your guidance.

Please let me close this post.

With regards,

JS Yoo

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TMS320F28069F: inverter for ACIMs : implementation of the high-side short current protection function