Electric Power Voltage Drop Solutions: Coil-Locks

Presented by: Power Quality Solutions, Inc. (PQSI) Knoxville, Tennessee USA

Symptoms of Electric Power Quality Problems.

Power Quality problems are failure or misoperation of customer end-use equipment caused by voltage, current or frequency deviations.

PQSI Coil-Lock Applications

Coil-Locks Eliminate Weak Links

Relays, contactors, and motor starters are used extensively in commercial and industrial facilities to control business machines and process equipment. These devices often have a low tolerance to electric service voltage and are frequently diagnosed as “weak links” in automated production lines.

Coil-Locks Eliminate Costly Equipment Shutdown

During common voltage, the solenoid coils in these motor-driven systems may de-energize long enough to cause the power circuit mechanical contacts to open (chatter), and the connected electrical equipment to shut down. The Coil-Lock eliminates costly process shutdown, installs in minutes, and can be a cost-effective alternative to other voltage protection methods.

Coil-Locks Eliminate Disruption of Operations

This situation can impact an entire manufacturing facility The Coil-Lock is available in different models to be compatible with most solenoid operated relays and contactors and is ideal for protecting master control relays, and E-stop circuits.


Note: There are > 240 facility voltage drops/year down to as much as 25% of nominal supply voltage that last for < 0.02 Seconds, and ~ 0 to 16 voltage drops/year that can last up to 3 Seconds.

* Survey Sources: Electric Power Research Institute (EPRI), Canadian Electric Associations (CEA), and National Power Laboratory (NPL).


Note: This slide illustrates the typical quantity and time durations recorded for the facility voltage sag events in the End Users Surveys* Some examples of utilizing this data are shown below:

Quantity 38 x 0.41% = ~ 16 Voltage Sag Events each year lasting ~ 2 to 10 Cycles

Quantity 38 x 0.22% = ~ 8 Voltage Sag Events each year lasting ~ 10 Cycles to 1 Second

Quantity 38 x 0.20% = ~ 7 Voltage Sag Events each year lasting ~ 1 Second to 10 Seconds

Quantity 38 x 0.07% = ~ 3 Voltage Sag Events each year lasting ~ 10 Seconds to 1 Minute

Quantity 38 x 0.04% = ~ 2 Voltage Sag Events each year lasting ~ 1 Minute to 5 Minutes

* Survey Sources: Electric Power Research Institute (EPRI), Canadian Electric Associations (CEA), and National Power Laboratory (NPL).


Note: This illustration depicts a voltage sag 50% depth with duration that can vary from 8 milliseconds to > 3 seconds due to across the line motors starting in industrial processes, air conditioners, and utility activities.


Note: This illustration depicts the Tolerance and Protection Curves for “Unprotected Solenoid Coils versus PQSI Coil-Lock Protected Coils.” The YELLOW shaded area suggests that unprotected solenoid coils will generally ride through voltage sags in this region.

The GREEN shaded area indicates that solenoid coils protected by a Coil-Lock will continue to keep their contactors/relays energized for voltage sags in this region.

In the RED shaded area, the solenoid coil is de-energized to maintain the safety functions for emergency stop circuits.


Note: This GREEN shaded area in this illustration depicts the typical SEMI F47 voltage sag tolerances that facility equipment is required to operate; i.e. 0% voltage input for up to 20 milliseconds; 50% voltage input for ~ 0.2 seconds; 70% voltage input for ~ 0.7 seconds; 80% voltage input for ~ 10 seconds; and 90% voltage input for ~ 100 seconds.


Note: This slide compares selective voltage sag protection options in their initial costs, installation costs, maintenance costs, and life cycle costs.