When it comes to protecting your industrial electrical systems from faults and overloads, you need a trip unit that's reliable, efficient, and easy to use. That's where the Digitrip series from Eaton comes in. In this post, we'll examine two of the top models in Digitrip’s lineup: the Digitrip 520 Series and the Digitrip RMS 310 Series.

Digitrip 520 Series Circuit Breaker Trip Unit

These include the 520i; and 520M, 520Mi, 520MC, 520MCi trip units and are for use only in Magnum and Magnum DS circuit breakers.

Product Details

The Digitrip 520 trip unit is primarily designed to safeguard electrical circuits from fault conditions. It does this by monitoring the secondary current signals generated by the circuit breaker's built-in current sensors. These sensors play a vital role in the trip unit's operation, detecting the electrical current flowing through the breaker and creating a proportional secondary current.

This secondary current serves two key functions:

• Powering the trip unit: The secondary current acts as the power source for the Digitrip 520, allowing it to operate independently without needing an external power supply. This self-contained design ensures reliable and autonomous protection.
• Fault detection: The trip unit constantly analyzes the secondary current signals to detect potential fault conditions. It compares the measured current levels and duration against preset thresholds and time delay settings.

In the event of a detected fault, the Digitrip 520 family of units prompts the circuit breaker to open, interrupting the electrical flow and protecting the connected equipment from damage. It even provides valuable information about the nature of the fault, categorizing the cause of the trip into one of the following modes:

• Long time trip: Indicates an overload condition where the current exceeds the preset limit for an extended duration.
• Short time trip: Signifies a fault condition where the current surpassed the predetermined threshold for a relatively short period.
• Instantaneous trip: Represents a severe fault condition that caused the current to rise above the instantaneous trip setting, requiring immediate interruption.
• Ground (earth) fault trip: Detects and responds to ground fault conditions, if the trip unit is equipped with this feature.

Principles of Operation

The Digitrip 520 series is built to handle the kind of temperature swings you see in industrial settings. We're talking anywhere from -20°C to +85°C, but most of the time, it's going to be in that 70°C to 75°C sweet spot. If things get too hot and the trip unit starts pushing those temperature limits—don't worry—it's got a built-in overtemperature protection feature, courtesy of the Eaton CHip™ (CutlerHammer Integrated Processor).

If that chip gets too hot under the collar, it'll trip the breaker to keep everything safe. And just so you know what's going on, the red Long Delay Time LED will start flashing to give you a heads-up.

The CHip™ doesn't work alone. It gets help from current sensors inside the circuit breaker. These sensors keep an eye on the current flowing through the breaker and send that information to the CHip™.

When the breaker does its job and carries current, the sensors generate a secondary current. This secondary current is important for two reasons. First, it gives the CHip™ the information it needs to protect itself. Second, it provides the power to trip the breaker if something goes wrong.

As the current flows, the sensors create analog voltage signals across the current viewing resistors. The CHip™ turns these analog signals into digital data that the microcomputer can understand.

Protection Settings

Before installing any circuit breaker, you must first configure the protection settings of each trip unit according to the values prescribed by the installation engineer.

To modify each setting, a small screwdriver is used to manipulate the corresponding rotary switch. The trip unit label clearly displays the chosen setting for each adjustment, ensuring easy reference and verification. It is critical that your rating plug aligns with the current sensors, as this determines the continuous current rating of the circuit breaker.

In the event of an automatic trip, triggered when the current surpasses the predetermined threshold, the LED in the appropriate segment of the simulated time-current curve will light red, indicating the reason for the trip. This visual clearly identifies the cause of the trip.

Digitrip RMS 310 Trip Units

The Digitrip RMS 310 is designed specifically for use with Series C L-Frame and MDL Frame Molded Case Circuit Breakers. At the heart of this trip unit is an integrated circuit that leverages microprocessor technology. One of the key advantages of the Digitrip RMS 310 is its self-contained nature. When the circuit breaker is closed, the trip unit does not require any external power source to function. Instead, it relies on current signal levels and control power obtained through built-in current sensors seamlessly integrated into the trip unit itself. This autonomous design ensures reliable operation and protection without depending on external factors.

Product Details

The Digitrip RMS 310 Trip Unit comes in four distinct variations. All trip units feature a fixed long delay time function, which can be adjusted by replacing the rating plug. And depending on the model, you can customize the trip unit with up to two phases and two ground (time-current) adjustments. This allows you to fine-tune the protection settings to suit your specific application.

Adjustment options for each model are as follows:

• LESxxxLS,-LSE,-LSP or MESxxxLS - Short Delay Pick-up
• LESXXXLSI,-LSIE,-LSIP, or MESxxxLSl - Short Delay Pick-up/Short Delay Time
• LESxxxLSG, or MESxxxLSG - Short Delay Pick-up/Ground Fault Pick-up/Ground Fault Time
• LESxxxLSIG or MESxxxLSlG - Short Delay Pick-up/Short Delay Time Ground Fault Pick-up/Ground Fault Time

Principles of Operation

The Digitrip RMS 310 was also designed to keep your circuit breaker in check. It, too, monitors the current flowing through the breaker and makes sure it stays within safe limits. If the current gets too high or stays on too long, the trip unit tells the breaker to open up and cut off the power.

It’s all driven by the Cutler-Hammer SpreTMchip. This chip has a built-in microcomputer that does all the numeric and logic functions needed to protect your system, pulling information from the current sensors inside the circuit breaker. When the current sensors notice that the current is too high, they alert the SpreTMchip, which then looks over the data to decide if the current has gone over the preset limits or has been on for too long.

If either happens, the SpreTMchip sends a signal to the flux transfer shunt trip. This tells the breaker to open up and stop the power from flowing.

Protection Settings

The secondary currents from these sensors provide the correct input information for the protection functions, as well as tripping power, whenever the circuit breaker is carrying current. These current signals develop analog voltages across the appropriate calibration resistors.

Digitrip RMS 310's has a microcomputer that continuously monitors and processes electrical data. It employs a cyclical approach, constantly scanning the voltage values across each calibrating resistor and storing these readings in its memory. The collected data is then utilized to perform precise calculations, determining the true RMS (Root Mean Square) current values. These calculated values are repeatedly compared against the preset protection function settings and other operational parameters securely stored within the memory. 

Based on this continuous analysis, the trip unit's software program intelligently decides whether to trigger protection functions. If necessary, it can initiate a trip command to the circuit breaker's flux transfer shunt trip device, effectively interrupting the electrical flow and safeguarding the connected equipment from potential damage.

A "Thermal Memory" effect prevents the breaker from re-energizing immediately after an overload. A "cooling off" period of up to 5 minutes is required, allowing cabling to cool off.

What Applications Are These Models Best Suited For?

Now, let's discuss a few industries, applications, and examples for both the Digitrip 520 and RMS 310 series trip units.

Digitrip 520 Series

Places like car factories, steel mills, and paper mills where big machines work non-stop, these trip units are crucial. They're put into Magnum and Magnum DS circuit breakers to protect important equipment like motors, conveyors, and hydraulic presses from getting overloaded or having short circuits.

For example, in a car factory where everything needs to be precise and efficient, Digitrip 520 trip units make sure that assembly line machines stay safe from electrical problems, which helps keep production going smoothly without any unexpected stops.

They're also important in places like chemical plants and refineries, where dangerous materials are handled. Here, safety protects people and the environment. Digitrip 520 trip units do a great job of preventing electrical fires and explosions by watching out for ground faults and overcurrents. For instance, in a refinery, these trip units are placed in circuit breakers to ensure essential equipment like pumps and compressors run safely, even in risky conditions.

Digitrip RMS 310 Series

Places like office buildings, malls, and hospitals, there are a ton of electrical systems working all the time—that's where the Digitrip RMS 310 trip units come in handy. They're put into Series C L-Frame and MDL Frame Molded Case Circuit Breakers to make sure that everything stays reliable.

For example, in a hospital where power is needed constantly for medical equipment, these trip units ensure that important circuits stay safe from problems, which is crucial for keeping patients safe.

In data centers, where there are many servers and networking equipment, having reliable circuit protection is key to keeping everything running smoothly. The Digitrip RMS 310 trip units do a great job of protecting against electrical faults, which helps prevent equipment from getting damaged and keeps data safe. For instance, in a big data center, these trip units are put into circuit breakers that protect things like server racks and networking gear, making sure that essential services keep running without any interruptions.

Your Authorized Digitrip Vendor Since 1974

Whether safeguarding critical equipment in heavy manufacturing plants or ensuring uninterrupted operations in commercial buildings and data centers, Digitrip trip units excel in guarding your electrical systems.

If you need top-notch circuit protection solutions, look no further than Wistex. As your one-stop shop for all things Digitrip, Wistex offers a wide range of products, including Digitrip RMS 310 trip units, Digitrip 520 series trip breakers, and much more—all available online. With fast shipping and the lowest prices guaranteed, trust Wistex to meet your circuit protection needs.