[erikjgreen]

Hi, all;

I'm installing some new servo drives in my mill (long story, but I'm doing version 2.0 of it, with maybe even version 3 down the line) and the servo drives' manufacturer recommends certain things for the power and servo wiring, one of which is inrush current protection. Their recommendation is an appropriate NTC thermistor.

I've acquired said thermistors and I'm wiring things up in my drive cabinet. However, I'm at a bit of a loss as to the best way to mount them. I have wiring running from the main (fused) switch in the cabinet to my servo drive transformer, from there to a distribution block, then to individual AC filters, then to the servo drives (these particular drives, Aerotech BA20, accept AC directly).

According to the manual, the thermistor should be placed serially on the "Hi" AC input line. That's fine, but no mention of a good way to do that.

The thermistor package is a ceramic coated disc with two stiff tinned leads on it.

My question is, how and where should I install it into the power wiring? I can't think of a good way to put it in there except maybe soldering it to the end of one wire and inserting the other thermistor lead into a screw down terminal, or maybe removing the bridge from the distribution block and bridging it with the thermistor.. if I could make that work it would take all load off the thermistor leads.

Is there such a thing as a DIN rail mountable terminal block that will accept a single through hole component? Maybe I could make one.

Also, should I mount the thermistor in the air flow that cools the drives, or not?

Thanks,
Erik

[keebler303]

Just use 2 normal DIN rail terminal blocks. Screw your NTC into the top terminal on both of them, then your power in and power to the drive to the bottom of the terminals.

Something like this: http://sub.allaboutcircuits.com/images/00450.png

[erikjgreen]

After seeing that, I feel like a complete idiot

I'll find some spare DIN rail space and use some terminal blocks to do this.

Should I let them get hot or keep them in the air blowing from the fan?

[keebler303]

I'd think they are designed to carry the rated current in still air, but it'd be wise to follow the manufacturers recommendation.