Terminal blocks

By Clarence Klassen 

I spend a lot of time with electricians. I also spend a lot of time with engineers and electrical designers. The electricians often talk at length about terminal blocks. They go on and on about crowded conditions, working on their knees, working in the dark, working by feel. Many times the connection is not made well the first time. Reconnecting the wire may damage the terminal block which may mean replacing the whole circuit card. See the photo above.

The conversation is much shorter when talking with designers and vendor representatives. Space is money. Smaller drives sell better than larger drives. 

I think the battle is over. Small crowded terminal blocks have won. Wiring and maintenance electricians have to learn to live with the situation.

Here are a few suggestions for better wiring on drive terminal blocks.

1-Work on a bench at a comfortable height. This can not apply to maintenance electricians
2-Trim wires to length (exact plus 1”/25mm). There is no space for extra wire length.
3-Use crimped ferrules on small gauge wires.
4-Use wire markers recognizing these cannot be read. They are needed for replacing circuits in the drives.
5-show wire colors on the electrical drawings.
6-Unplug terminal blocks or option modules when making connections.
7-Use a guide for stripping wires to the correct length
8-Use the recommended crimping tool.
9-Test connections by pulling on the wire. No loose connections.
10-Inspect each connection. No insulation under the connections.
11-Use adequate lighting. Cabinets should be illuminated.
12-Wear knee pads or kneel on padding.
13-Position wire markers so they are right-side-up and as visible as possible.