# Insulation Monitoring Device



## peterguy (Jun 18, 2012)

Hi iruraz,

we are using exactly those IMUs from Bender.
They are reliable, quite accurate, easy to use and (unfortunately)expensive.

What I really like is the PWM Output that gives you all the information you need.

Regards,
Peter


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## marc02228 (Jan 15, 2011)

peterguy said:


> Hi iruraz,
> 
> we are using exactly those IMUs from Bender.
> They are reliable, quite accurate, easy to use and (unfortunately)expensive.
> ...


I agree 100%. I installed it into my Miata and use an Arduino board to display the insulation value on a simple 16x2 display. Works great.


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## racunniff (Jan 14, 2009)

peterguy said:


> Hi iruraz,
> 
> we are using exactly those IMUs from Bender.
> They are reliable, quite accurate, easy to use and (unfortunately)expensive.
> ...


This is intriguing. Where did you find them?


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## iruraz (Sep 4, 2012)

peterguy said:


> Hi iruraz,
> 
> we are using exactly those IMUs from Bender.
> They are reliable, quite accurate, easy to use and (unfortunately)expensive.
> ...


Hi Peter,

It is nice to see you  As you mentioned above it indicates situation via PWM and it seems very useful. I will contact Bender but before is it possible to inform me about its price?

And I have technical question about it. Do you connect it to VMU (Vehicle Management Unit) for controlling contactors in case of danger?



marc02228 said:


> I agree 100%. I installed it into my Miata and use an Arduino board to display the insulation value on a simple 16x2 display. Works great.


@marc02228 thanks. I looked your ev blog but it is German and I could not find anything about Bender IMU.


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## peterguy (Jun 18, 2012)

Hi iruraz,

its a pleasure 

The bender costs something around 400 or 500 Euros, as far as I remember.

Yes it is connected to our ECU which continuosly reads the resistance value. It depends on your philosophy (and on the regulations, of course), how you react in case that the insulation goes below a certain threshold.

Opening the contactors while the car is driving is dangerous, too!

A good idea might be to give a warning to the driver, in case that the insulation problem occurs while he is driving.
In case that the insulation problem is detected before the start, its possible to not allow a start.

Hope this helps,
Peter


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## iruraz (Sep 4, 2012)

@peterguy,



> The bender costs something around 400 or 500 Euros, as far as I remember.


As you mentioned before it is expensive. But it is an obligation for monitoring leakage current. Do you know any other products for insulation monitoring?



> Yes it is connected to our ECU which continuosly reads the resistance value. It depends on your philosophy (and on the regulations, of course), how you react in case that the insulation goes below a certain threshold.
> 
> Opening the contactors while the car is driving is dangerous, too!
> 
> ...


Your advice is make sense. By the way, do you use Neuro (TM4) as a controller or VMU? Thanks for your help.

Kind regards.


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## peterguy (Jun 18, 2012)

Hi Iruraz,

Sorry, I only know the Bender IMUs.

We don't work with the Neuro, we use a special, inhouse developed, ECU as VMU.

Regards,
Peter


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## iruraz (Sep 4, 2012)

peterguy said:


> Hi Iruraz,
> 
> Sorry, I only know the Bender IMUs.
> 
> ...


@peterguy, it is ok. I really wonder your "inhouse" products and your team  Thanks for your helps.

Best regards.


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## marc02228 (Jan 15, 2011)

iruraz said:


> Hi Peter,
> 
> It is nice to see you  As you mentioned above it indicates situation via PWM and it seems very useful. I will contact Bender but before is it possible to inform me about its price?
> 
> ...


You can use the google translator to read the blog. But I didn't write much about the IMU. It's really easy to handle. In the 3rd picture you see the display, which is used to display the isolations resistance.


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## iruraz (Sep 4, 2012)

marc02228 said:


> You can use the google translator to read the blog. But I didn't write much about the IMU. It's really easy to handle. In the 3rd picture you see the display, which is used to display the isolations resistance.


@marc02228 thanks for your reply. Is it possible to share more technical detail about it? For example, why did you display "isolation resistance"? Why didn't you display voltage difference between HV and LV?

And there is an expression which I could not understand in its datasheet. Is there anyone to know meaning of "Automatic adaptation to the existing system leakage capacitance (=< 1uF)" ?



Regards.


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## PStechPaul (May 1, 2012)

There are various pieces of test equipment, and several methods, for testing insulation integrity, but mostly they are performed occasionally for preventive maintenance and not continuously monitored as these devices seem to do. I am somewhat familiar with some of these:
http://www.sefelec.com/en/insulation-resistance-test.php
http://ecmweb.com/content/what-insulation-testing
http://www.transcat.com/PDF/BasicInsulationTesting.pdf

A very interesting method is Time Domain Reflectometry, which can locate various faults in cables and may have application in EV power systems:
http://en.wikipedia.org/wiki/Time-domain_reflectometer

I found other sources for insulation monitoring devices:
http://www.baronpower.com/insulationmonitoring.html
http://www.deif.com/Ecom/Marine_-_O...Equipment/Products/Insulation_Monitoring.aspx
http://www.megacon.com/default.aspx?pageId=236

I would think a GFCI would accomplish much the same thing at a lower cost.


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## peterguy (Jun 18, 2012)

iruraz said:


> And there is an expression which I could not understand in its datasheet. Is there anyone to know meaning of "Automatic adaptation to the existing system leakage capacitance (=< 1uF)" ?
> 
> 
> 
> Regards.


I have only little understanding of this point, but since we had to fight with it once, I'll try to explain what I understood. Maybe someone else can explain better:
Due to the isolation between earth and HV, your system acts also as a capacitor. This capacitance is called leakage capacitance. Depending on the size of your system (mainly length of cables, number cells, layout of cells) it can be bigger than 1µF. This will lead to erronous measurements, since the Bender is not able to drive the load. 

Don't worry, for a normal car layout this point is not interesting for you. With a (very big) stationary system we had once trouble using the Bender IR155 and had to upgrade to device which is capable of up to 5µF if I remember correctly.


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## iruraz (Sep 4, 2012)

@PStechPaul, thanks for the links. As you mentioned above they are not continuously monitoring device. 



> I would think a GFCI would accomplish much the same thing at a lower cost.


I will seek for it. But Bender seems the most appropriate one (without its price  )

@peterguy,



> I have only little understanding of this point, but since we had to fight with it once, I'll try to explain what I understood. Maybe someone else can explain better:
> Due to the isolation between earth and HV, your system acts also as a capacitor. This capacitance is called leakage capacitance. Depending on the size of your system (mainly length of cables, number cells, layout of cells) it can be bigger than 1µF. This will lead to erronous measurements, since the Bender is not able to drive the load.
> 
> Don't worry, for a normal car layout this point is not interesting for you. With a (very big) stationary system we had once trouble using the Bender IR155 and had to upgrade to device which is capable of up to 5µF if I remember correctly.


Thanks for the explanation. At least I have a general opinion about it. I am keeping to search it in electronic forums.


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