Coil-Locks: What They Are, and Why You Need Them

The Unseen Issue

The wires carrying current have an innate resistance, or impedance, to the flow of current. How much voltage is lost due to that impedance is known as Voltage Drop. Voltage Drops can occur from variables outside of a company’s control like Utility System Faults, Motors Starting, Load Variation, and Weather Conditions.

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 sags and are diagnosed as “weak links” in automated production lines. During common voltage sags, the solenoid coils in these motor-driven systems may de-energize long enough to cause the power circuit mechanical contacts to open, and the connected electrical equipment to shut down. If the voltage drop is severe it can create issues with whatever device is receiving power, in turn, this causes the device to work harder and consume more power than necessary.

The Financial Impact

This is an important issue to solve as momentary voltage drops are responsible for billions of dollars per year in lost revenues to manufacturing and process industries. Additionally, this situation can disrupt business operations and impact an entire manufacturing facility. This in turn adds additional financial losses, making the overall negative impact far greater than just the extra energy that is consumed.

The Answer: Coil-Locks

The Coil-Lock is designed to ensure that at any time input voltage is present (down to ~25% of nominal voltage), the protected AC coil will maintain enough energy to hold in the critical process element. When the input voltage goes below 25% of nominal, the Coil-Lock releases the coil, thereby ensuring that safety is not compromised, and the “on/off state” operation of the existing process functions as intended. The key to properly applying Coil-Locks is to determine the DC resistance of the AC coil of the relay/contactor unit you want to protect from deep voltage sags. Once you have the AC coil’s DC resistance value, the next step is to select the appropriate model Coil-Lock. Click here to see all Coil-Lock Models.

The Coil-Lock eliminates costly process downtime, installs in minutes, and can be a cost-effective alternative to other voltage sag protection methods. The Coil-Lock is available in different models to be compatible with most relays, contactors, or solenoid coils and is ideal for protecting master control relays, and E-stop circuits.

Coil-Lock Specifications:

[1] Provides continuous output voltage to hold in relay and contactor coils for all IEEE Std.P1159 defined voltage sags to approximately 25% of nominal.

[2] Designed to act as a discrete on/off device and will turn off the coil voltage if the Coil-Lock input voltage is interrupted beyond a few cycles (depending on the relay/contactor rating and vendor model).

[3] Provides required high inrush coil current during startup.

[4] Provides transient voltage surge suppression for the relay/contactor coil circuit.

[5] Designed to survive ANSI/IEEE C62.41 Category A and Category B defined transient voltage surges to 6kV/500A.

[6] Designed to be compatible with stress and vibration common to typical commercial and industrial applications.

[7] Ambient Operating Range: -29° C (-20°F) to +55° C (131°F).

PQSI Coil-Lock Warranty:

Unconditional free Coil-Lock replacement for one year from date of purchase. Neither PQSI nor its business associates are responsible for any production loss or damage caused by a Coil-Lock misapplication or Coil-Lock failure.

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