MCCB settings control tripping parameters and define how the breaker operates to protect an electrical circuit or piece of electrical equipment. These settings are important for the safe operation of an electrical system, and must be correctly adjusted. This explainer post will help you to help you understand the basics of MCCB trip settings.
MCCB settings refer to the configurations that allow you to customize the protection of a circuit. These can be adjusted to deal with certain types and levels of electrical overloads and other issues that create electrical risks as residual or earth leakage currents.
Because the MCCB thermal magnetic settings are adjustable, it is important to understand what each setting does and how they should be adjusted depending on the type of application.
That way, you’ll not only ensure that your electrical system and equipment are adequately protected, but also that the MCCB is not overtaxed. Below are some of the common MCCB current settings that you should know about.
MCCB Settings Explained
MCCB settings are generally divided into three different categories: overload setting, overcurrent setting, and ground or earth fault protection setting. Here is a brief explanation of each setting, including the parameters that you can adjust.
MCCB Overload Setting
This MCCB setting range adjusts the maximum acceptable current allowed to pass through the breaker without causing it to trip. That means setting parameters based on the current/load requirements of your system. The MCCB overload setting generally involves the following variables.
Long Pickup Current Setting
This MCCB trip setting is denoted by Ir. It defines the breaker’s continuous amperage rating and is time-delay adjustable. That means once set, the MCCB will trip if the current exceeds the specified current level, but after the set pickup time delay, thus allowing for higher startup currents.
Normally, this MCCB tripping time setting prevents the breaker from tripping if the current below 105% the Ir current. This helps avoid nuisance tripping, which is when a breaker trips unexpectedly due to momentary high currents.
Long Time Delay Setting
Usually expressed as tr, this setting specifies the time delay before the MCCB trips if it detects an overload. The MCCB setting range for this parameter varies by 2.2 seconds to 27 seconds and as high as six times the breaker’s current rating.
Essentially, the longtime delay setting has an inverse relationship with the current rating of the breaker. If the current increases, the MCCB tripping time decreases. This setting serves to allow temporary current increases, such as those resulting from motor inrush currents, to pass without tripping the breaker.
The overcurrent setting for MCCB tripping and protection refers to the magnetic trip adjustment of the breaker. This is the breaker’s protection against short circuit. Unlike the above MCCB settings for overload, the overcurrent setting provides instantaneous tripping and can be categorized into 3 different settings.
Short Time Pickup
This is essentially a setting to allow for the selective tipping of the MCCB circuit breaker. It basically allows downstream faults to clear without necessarily affecting the upstream circuit and its equipment.
Generally, this is set at 1.5-10 times the MCCB Ir setting current or the setting for trip unit amperage. As an example, you may adjust a 600A MCCB to trip at between 1200 amps and 6000 amps.
Short Time Delay
Short time setting defines the time allowed before a short time pickup trip of the circuit breaker. AS such, this MCCB current setting is usually used alongside the short time pickup setting explained above.
Normally, two different modes are available, the fixed time mode and the I2t mode. The fixed time mode allows for a specified time delay to be set, usually ranging between 0.05 – 0.5 seconds, with the trip timing remaining constant regardless of the level of current that causes it.
The I2t mode uses different time settings depending on the current levels that cause them, and can be set to trip at between 0.18 to 0.45 seconds. This presents a more efficient use of the breaker as it allows for quicker trips of higher currents, while still providing protection against lower current levels.
Instantaneous Current Setting
This MCCB protection setting is expressed in terms of Ii and represents the breaker’s protection against very high short circuit currents. Because of the higher current levels, this setting trips the breaker almost instantaneously, without any intentional delay.
Generally, this setting is programed to trip the breaker at 2 to 40 times the breaker rating for continuous current. That means that a breaker rated for 100A, could trip at 200 to 4000 A of current
The instantaneous MCCB adjustable setting should be set carefully according to the application, as it trips the breaker faster than other settings and can cause frequent false trips if not set correctly.
Note that this setting cannot be used in isolation, as it should always be combined with the short time and longtime settings.
Ground Fault Protection Setting
MCCB settings also often include a ground fault protection setting for the circuit. This helps to protect the circuit from a ground fault, which occurs when electricity passes through an unintended path and is diverted to the earth or another grounded surface.
These MCCB protection settings are typically adjustable depending on the type of application. Essentially, it allows for an adjustment of between 20- 70% the breaker’s rated current. The most common MCCB settings for ground fault protection include the following:
- Earth protection time delay setting
- Setting to monitor the current passing through the phase and earth
- Setting to adjust how sensitive the breaker is to ground faults
- Setting to adjust the length of time before the breaker trips after a ground fault has been detected.
Ground fault MCCB settings work together to help protect your circuit or equipment and allow you to determine the exact level of protection needed for each specific situation.
Overall, adjusting the right MCCB settings is essential for proper circuit protection. It ensures that your electrical system maintains optimal safety and performance.
Different MCCB settings control the way the circuit breaker responds to various conditions. The long pickup current, long time delay, overcurrent, and ground fault settings all help to protect the system from overloads, short circuits, and grounding problems. Adjusting them correctly ensures that your electrical system operates safely.
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