1500 vdc alarm circuit ?????

[omid_juve]

the power supply of our metro train is 1500 vdc that will come to the train with pantograph . we are here a maintenance staff of the train . so sometimes its needed to go to the roof of the train when it is parked in parking for this purpose we should have an automatic locker that sense the voltage of overhead centenary network and if the voltage is higher than zero it locks the door and doesn`t let it to be opened for any person to go to the roof. so i want to design this locker . first step i find a voltage sensor 1500/40ma to get sample from the network voltage and then i want to use comparator using op amp to check if the voltage is higher than zero locks the door .
so please guide me what precautions should i use in my design for this type of circuit because it is related to life of a human .

 

[srizbf]

the power supply of our metro train is 1500 vdc that will come to the train with pantograph .
... first step i find a voltage sensor 1500/40ma to get sample ...

what is this 1500/40ma voltage sensor?

do you have any sensor already (may be supplied by the loco manufacturer)?

 

[schmitt trigger]

what is this 1500/40ma voltage sensor?

I think he may have meant a 1500 volt to a 20 mA loop converter.

 

[e_bettio]

I had to do something similar once. I made a voltage divider out of resistors. I used a series/parallel combination to drop the voltage significantly. The resistors I used were Phillips VR68 series. I then potted the whole thing in epoxy. The output was a voltage of course, not a 20mA signal.
Eric

 

[omid_juve]

I had to do something similar once. I made a voltage divider out of resistors. I used a series/parallel combination to drop the voltage significantly. The resistors I used were Phillips VR68 series. I then potted the whole thing in epoxy. The output was a voltage of course, not a 20mA signal.
Eric

please look at the attachment it is the datasheet of the sensor that i want to use . but my question is another thing .it is about how i can design this circuit to be so safe . for example if some thing is burned inside the circuit it doesn`t cause the door to be opened when we have voltage on the network . because it is very degerous

 

[BradtheRad]

for example if some thing is burned inside the circuit it doesn`t cause the door to be opened when we have voltage on the network

Your system should have redundancy built in. In other words, a backup alert.

For instance, a second detector, such as a non-contact detector. A few are described in this article:

http://www.homeinspect2020.com/uploads/Non_Contact_Voltage_Testers_and_Personal_Risk_Management.pdf

It may be possible to adapt one of these, or even a gas-filled (neon?) bulb, so it lights up when 1500V is within a few inches. Then mount a light sensor nearby. Amplifying circuitry can activate a device such as lights, signs, beeper, door-lock, etc.

 

[omid_juve]

please look at the attachment it is the datasheet of the sensor that i want to use . but my question is another thing .it is about how i can design this circuit to be so safe . for example if some thing is burned inside the circuit it doesn`t cause the door to be opened when we have voltage on the network . because it is very degerous

this is the attachment

 

[srizbf]

Have you made any attempt to test with the sensor for the alarm?

 

[chuckey]

That transducer is for AC, you said in your text that the system is 1500V DC.
Frank

 

[chuckey]

Sorry top line of spec says 2500 VRMS, further on says DC.
Frank

 

[crutschow]

................ but my question is another thing .it is about how i can design this circuit to be so safe . for example if some thing is burned inside the circuit it doesn`t cause the door to be opened when we have voltage on the network . because it is very degerous

The circuit should be designed with double or triple redundancy so that at least two totally separate circuits have to agree that there is no voltage before the door can be opened.
This should be a total separate redundancy with a separate door latch for each redundancy.
And the door should be latched with no power to the door. Power would be need to be applied to both latches before the door will open.