Induction/Noise

Alan Case

Lifetime Supporting Member
Join Date
Apr 2002
Location
Wagga Wagga
Posts
1,268
Hi, Wondering if anyone has ever installed 24VDC limit switches and PE sensors in close proximity to a railway track. The track is the return of a 25kV AC electric train system. In theory the voltage at the track is zero or ground potential and the current would not be excessively high as the trains are 25kV. What I am worried about is inductive voltage or noise on the signal wires feeding to the PLC.
Well not quite a PLC but a safety relay that uses 24V DC test pulses. ie 24 V is output from the relay with a millisec gap in the voltage level at a specific timing. There are 4 distinct test pulses and each one uses a different timing. The inputs of the relay monitor this 24V and also looks at the pulse timing to ensure it is the correct signal.
Any comments.
Regards Alan Case
 
I suggest you use shield, twisted pair for each signal. Multi pair encoder cable might be good for this.

I would also extablish the shield ground point at a terminal strip for the wires leaving the control panel. Then take the shields from the relay wiring and ground them at the same terminal. Once you have all shields on a common ground bus, ONE wire to actual earth ground.

I have also found 0.1uf 100 vdc mylar caps make excellent filters. They get rid of the fuzz and spikes but do not seem to affect anything including encoder signals.

BTW, even though you might have low or zero volts, if it is a return path, there is current and with current there is magnetic fields.
 

Similar Topics

Is there any issue with running a VFD-controlled 3-phase induction motor in torque control mode in the braking region continuously (back-driven by...
Replies
14
Views
3,952
Hello everyone! I'm new here and this will be my first post so hopefully I can get some help, I'm having a hard time wrapping my head making some...
Replies
11
Views
4,614
Why it is said Maximum torque of induction motor is inversely proportional to frequency square ? Maximum torque formula for induction motor is...
Replies
13
Views
4,330
I have an auger powered by an induction motor under flux vector torque control driven by a PowerFlex755. According to my log, the command velocity...
Replies
12
Views
4,944
As you know there are three region for induction motor's operating. What I'd like to ask if motor is regenerating energy during plugging which...
Replies
2
Views
1,522
Back
Top Bottom