Motor Connections That Keep You Running - Low Voltage Applications
Proper motor connections are an essential part of a reliable motor circuit, but are often overlooked. Unfortunately, our test teams and repair stores continue to find high resistance and ground connection problems caused by
- Vibration
- Heat
- Moisture
- Contaminants
- Improper handling
- Compression in Jbox (too small)
The two areas that need to be considered for improvement are the connection itself and the insulation. The connection should be mounted in a junction box with some distribution of movement and must have a mechanical connection strong enough to maintain integrity during temperature changes and sustained vibration.
Things to consider and avoid when connecting motor leads:
- Connections will need to be "disconnected" in the future! Make a connection that can be opened without unnecessary work.
- Avoid wire nuts and crimp connections (low voltage and single phase applications) as they often fail prematurely.
- Although the primary cause is uncertain, we often find high resistance connections to "gel-cap" devices, so you may want to consider avoiding them.
- Most junction boxes are not designed to accommodate three (or more) sets of fully wrapped open bolts.
Some suggestions for good motor connections
Our winding team specify soldered lugs for all internal work. This is not always practical in the field, therefore:
- Use bolted compression lugs as standard, such as T&B Color-Keyed.
- Apply a joint compound such as T&B Kopr-Shield or Aluma-Shield to reduce resistance and prevent corrosion.
- Use compression lugs appropriate for your motor cable type. This is a topic that deserves additional coverage, so we may publish another article on it.
- Secure your lugs together with quality fasteners, including open washers (peace washers) or better yet, bainite washers (peace washers).
Be sure to match the lug to the cable and size. Most lug manufacturers offer a variety of application tools to support the lugs, such as colorful T&B keyed wall charts.
For easy and quick disconnection of low-voltage motors, consider using T&B Motor Lead Disconnectors. They take up more space, but can provide faster working connections in the right environment. Some benefits include:
- Compression connectors
- Snap-together disconnect without bolts
- Molded insulating sleeves without tape