Megatiker M4 Circuit Breaker Maintenance

3000 590 0.98×In

4000 520 0.93×In

5000 460 0.90×In

3.4 DC Application

Megatiker M4 can be used for DC circuits. The specific DC rated values should refer to Table B (not fully listed in this data sheet, but typical connection methods are: 1-pole for 60V, 2-pole series for 110V, 3-pole series for 250V, 4-pole series for 500V). Note that the DC polarity can be connected arbitrarily.

Release curve and protection characteristics

4.1 Thermal Magnetic Release Curve

The standard thermal magnetic trip curve (see Figure 9.1) is divided into:

Hot trip (overload protection): bimetallic strip with inverse time characteristic. The long delay setting current Ir can be adjusted through a dip switch (the specific range is not listed in this table, but is usually 0.4~1 × In).

Magnetic tripping (short circuit protection): instantaneous tripping, fixed multiple (about 10-12 × In).

The "cold state" and "hot state" in the curve correspond to the difference in operating time of the circuit breaker when the starting temperature is different. When selecting, it should be ensured that the instantaneous short-circuit tripping value is lower than the expected short-circuit current of the line and higher than the maximum load peak current.

4.2 Characteristics of Energy I ² t

Figure 9.2 shows the relationship between the allowable passing energy (I ² t) of the circuit breaker and the expected short-circuit current at different levels of breaking capacity. This parameter is used for selective coordination with downstream devices (cascade protection). For example, when the expected short-circuit current is 50kA, the energy passing through is about 10 ^ 6 A ² s. When designing, it should be ensured that the lower level equipment can withstand this energy without damage.

4.3 Cut off peak current characteristics

Figure 9.3 shows the relationship between the actual allowable peak short-circuit current (Ipk) and the expected symmetrical short-circuit current (Icc) under different breaking capacities. Due to the current limiting effect of the circuit breaker, the actual peak current passing through is much lower than the expected peak. For example, when the expected Icc is 100kA, the actual peak value is about 25kA. This characteristic is crucial for the dynamic stability selection of downstream components (contactors, cables).

Key selection points:

Selection of breaking capacity: determined based on the expected short-circuit current at the installation point. For systems with large transformer capacity and short busbar length, H or L level (70/100kA) should be selected. A general industrial power distribution of 50kA is sufficient, and a terminal circuit of 36kA can meet it.

Pole selection: 3P is used for three-phase three wire system; 4P is used for three-phase four wire system (can simultaneously disconnect neutral wire); 3P+N/2 (T742 series) is used for specific neutral wire protection requirements.

Installation methods: fixed type (directly fixed with screws), plug-in type (quick replacement through base, additional terminal and base need to be ordered), pull-out type (with Debro lift mechanism, can be shaken out for maintenance). Pull out type is suitable for situations that require frequent maintenance or backup.

Attachments and Extended Features

Megatiker M4 offers a wide range of on-site installation accessories, which are classified and introduced below.

5.1 Earth Leakage Modules

Standard type: T7082/400 (suitable for ≤ 400A), T7092/630 (suitable for 500-630A).

LED indicator type: T7081/400, T7091/630.

Features: Electronic, adjustable residual current of 0.03/0.3/3/3A, optional delay time of 0/0.3/1/3s. Suitable for TN-S systems. It can only be installed under the circuit breaker (under mounting) and cannot be installed side by side. The LED type has 50% ground fault detection contacts.

5.2 Release Accessories

Split release:

Voltage specifications: 24V, 48V, 110-130V, 220-250V, 380-440V (AC/DC universal).

Operating voltage range: 70%~110% Ue.

Action time: ≤ 50ms, power consumption 300W/VA.

Undervoltage release:

Voltage specifications: 24V DC, 24V AC, 48V DC, 110-125V AC, 220-240V AC, 380-415V AC.

Delay undervoltage module (800ms): M7000E/024 (24V ac/dc), M7000MR/230 (230V ac), M7000MR/400 (400V ac).

The universal release M7TMEV can be equipped with a delay module.

5.3 Auxiliary contacts

Standard auxiliary contacts: M7X01, 1C/O (conversion contacts), 3A-250V AC.

Configuration: M4/MS4 can accommodate up to 2 auxiliary contacts, 1 fault signal contact, and 1 release.

Fault signal contact (CTR): Indicates that the circuit breaker has tripped due to a fault (overload/short circuit), rather than human operation.

5.4 Operating mechanism

Rotating handle:

Directly installed on the circuit breaker: M7447 (black standard), can be equipped with M7R14 red/yellow handle.

Variable Depth Handle (IP55): T7449 (Black), T7449E (Emergency Red/Yellow).

Handle locking accessory: M7R17 (to be used in conjunction with universal key locks M7K01~M7K04).

Electric operating mechanism:

Direct action type (suitable for general operation): M74D230 (230V AC), direct drive, suitable for frequent opening and closing but low speed requirements.