I have found myself in an interesting scenario that is actually more mechanical in nature but maybe you guys can point me in the right direction.

I am having a hard time finding any ISO, IEC, or ANSI specs that dictate a proper way to calculate the force required needed to make a bolted-jointed connection using a terminal on top of a bus bar.

Problem Statement: I need to find the torque value required for my bolted connection that can easily see 2,000Volts.

I am using a Burndy compression lug with M12 hardware. Burndy gives no recommended torque value and said it is dependent on the hardware.

For the 10.9 Grade hardware I am using, with a 75% proof load, this value is 70FT*lb. Very easy to get this information, no problem here.

The problem is, I am using a belleville washer, the supplier for the belleville washer is saying I should not exceed 40 ft-lb, and they are recommending 26-34ftlb. 34ftlb will fully flatten the belleville washer. Let's go with the average here and roll with 30Ft*lb.

Assuming the bus bar and terminal I am using will not yield to 30ft-lb (I am still waiting for exact copper grade from these suppliers so I can get the exact yield strength), but now I am worried that maybe 30FT-lb isn't enough for this connection regarding the clamp force needed between my terminal and bus bar.

Any advice? Any standards that someone may know of? Any electrical drive guys out there? :)

  • \$\begingroup\$ most important action is that you remove any tarnish from the spot where the lug will be bolted down. Without a clean contact, all else is useless. \$\endgroup\$ – analogsystemsrf Aug 16 '19 at 3:08
  • \$\begingroup\$ Consider using a different washer - there are other licking methods. \$\endgroup\$ – Solar Mike Aug 16 '19 at 4:35

1kV should not be the spec rather , you want a gas-tight (oxide-free) joint to Not exceed xxx microhms. xxx=TBD.

This is easy to measure with say 10A and 1mV resolutution.

In my experience the shear forces of the threads and number of threads allowed me to easily achieve 100mohm max. This was my design and was approved by UL for an earth bond connection over power-coat painted sheet metal chassis.

I relied on the surface area of the threads between two nuts on a welded stud AND a sharp star washer interface to gouge between the crimped circular lug and the nuts to meet an IEC spec for ground wire to chassis spec. Torque was not important in this design to meet 100 mOhm max with lots of margin.


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