I need help with choosing the proper IDM(Insulation Monitoring Device)

Thread Starter

marksmandantus

Joined Mar 4, 2024
3
Hi guys I am new in this sector and I am trying to learn something about how to make an EV with my friends. My friends wanted me to research some IDM modules. I searched a lot and I tried to understand the sub-systems. But I didn't understand how do these IDMs work. I have to choose the proper IDM for our EV. It is a small EV(2 seats, 300kg). Can you help me to find a good IDM? Any suggestions? Or how can I create them and how does it works?

Thanks.
 

MisterBill2

Joined Jan 23, 2018
18,519
OK, here is a response: First, I am guessing because a lot of information is not provided.
The first guess is that the intention is to monitor some electrical circuit at some unknown voltage level to detect electrical leakage between some sort of conductors.
The request is to be able to do this with some sort of module available from some vendor, probably from an on-line seller.
Certainly it is fairly simple to sense the failure of electrical insulation, but with the lack of any detailed information there is no way it can be done adequately for anything close to a reasonable price.

What is needed is: what voltage is there between the insulated items? What current flow between the items constitutes an insulation failure?
 

Thread Starter

marksmandantus

Joined Mar 4, 2024
3
OK, here is a response: First, I am guessing because a lot of information is not provided.
The first guess is that the intention is to monitor some electrical circuit at some unknown voltage level to detect electrical leakage between some sort of conductors.
The request is to be able to do this with some sort of module available from some vendor, probably from an on-line seller.
Certainly it is fairly simple to sense the failure of electrical insulation, but with the lack of any detailed information there is no way it can be done adequately for anything close to a reasonable price.

What is needed is: what voltage is there between the insulated items? What current flow between the items constitutes an insulation failure?
Hi, these insulation monitoring device should observe and take care of insulation leakages between battery and car's chasis. If there is a leakage the device should alarm the driver by making noise (about 80db for 2m). The battery provides 48 volts. I know that it is not that much but the competetion force us to replace an IMD into the car system. I haven't got much time and knowledge to produce it myself. I wanted to find a proper device. Can you reccommend any device?
 

MisterBill2

Joined Jan 23, 2018
18,519
Any current leakage in an automotive power battery system is a serious problem. So leakage current IS AN ISSUE. Now that part makes some sense.
So now more questions: First, is either side of the 48 volt battery circuit intentionally tied to the chassis?? Or is any portion of the electrical system at all connected to the car's frame or chassis? Then one more question: Is that 48 volt battery composed of four similar 12 volt sections? or possibly two sections of 24 volts each?? Having a center connection to the battery voltage would allow a very simple leakage current detection scheme.
Then I must ask, because of the reference to "the competition", if you are part of an organization that produces electric vehicles, rather than one person building an electric vehicle for themselves? If you are a student and the competition is between schools, that will be interesting indeed.
Please answer the question about the battery soon, I have a simple scheme that can work , depending on the configuration.
 

Thread Starter

marksmandantus

Joined Mar 4, 2024
3
Hi again, the battery will be 6 cells each are 8 voltages. is not connected to the chasis. Battery is connected to the motor driver. In the case of a leakage into the chasis from cables, battery phases, or etc. the insulation monitoring device should warn the driver.I attached an image of leakage situation and how can it be dangerous when we touch to chasis. The competition is national, in Turkey called "Efficiency Challenge". In my team there are 3 parts : software, electrics and electronics, mechanics. I am into the electric and electronics team and we all have different duties. Some of us deal with motor driver, scheme designing , calculate the values etc. and my duty is find a good IMD. As I mentioned I am not good at it , I am not a technician :D so I need help to find an IMD.IMD.jpg
 

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MisterBill2

Joined Jan 23, 2018
18,519
OK,Here is the way that a proven "ground detection " system works. The midpoint of the battery system is used as the reference point, which means that the midpoint will be 24 volts different from each end of the battery system. Then a current sensing relay will connect between that midpoint and the vehicle chassis frame. Then if there is any insulation failure, current will flow thru the relay and make the alarm sound the warning.
Just one sensitive relay and one noise-maker to warn the driver. No complicated electronics circuit and no current drain when there is no alarm.

A similar scheme has been used by a MAJOR auto company to monitor teir production equipment control circuits for at least 25 years. The same principle, but with AC power.
 
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