Wiring Device Innovation – Motor Control

I've been installing and troubleshooting motors for over 30 years. The 
majority have been three-phase motors. They've range in size from 
fractional horsepower motors to those up to 350 horsepower.<br><br>Through the years, I've watched the evolution of motor control devices, particularly disconnects and manual motor controllers. Hubbell Wiring Device-Kellems

Steve Maurer, IME

I've been installing and troubleshooting motors for over 30 years. The majority have been three-phase motors. They've range in size from fractional horsepower motors to those up to 350 horsepower.

Through the years, I've watched the evolution of motor control devices, particularly disconnects and manual motor controllers.

OSHA regulations require a line of site disconnect for machinery, either mounted on or within view of the device. That means that in harsh environments, the disconnect must be able to withstand whatever is thrown at it.

In processing plants, for example, daily wash-downs with harsh acidic or caustic chemicals wreak havoc on them.

Of course, stainless steel enclosures help. Even then, there is always the chance that water and chemicals can enter and destroy internal components. The enclosure door or entry plate has always been a point of contention.

One of the newer designs incorporates what I refer to as a mailbox shape. Not only does the top of the enclosure slope forward, but it's rounded as well. Instead of a hinged door, the faceplate is bolted to the front of the enclosure. Hinged doors always had an issue with wash-down spray entering from the back, compromising the gasket or seal.

The mailbox "roof" actually extends beyond the front of the plate, forming a sort of overhang. This design excels at shedding water and keeps high pressure water streams from breaking through the seal as easily.

As NSF International standards have gotten more stringent, the enclosures must evolve to meet those regs. For example, labeling must withstand the onslaught of water and chemical. To combat this, some are removing labeling altogether and embossing information such as on/off position directly on the plate.

There have also been innovations in troubleshooting assistance. As LED technology makes its way into the workplace, it is now being incorporated on motor disconnects.

Installed on the faceplate of some enclosures, two rows of 3 LEDs each indicate the presence of power. The top three are illuminated to show that three-phase power is present at the top of the switch.

Three more under them indicate power leaving the switch. An unlit LED not only indicates a loss of power, but also assists in tracking down the problem.

This also adds to worker safety when performing lockout/tagout. With the switch in the OFF position, the bottom LEDs should be unlit. If not, this indicates a switch malfunction that must be addressed before servicing the motor.


Photo courtesy of Hubbell Wiring Device-Kellems