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Square D MHL3645025DC3903 Molded Case Circuit Breaker
- 450A
- 3 Pole
- Unit Mount
Square D
MHL3645025DC3903
Molded Case Circuit Breaker
Brand
Square D
SKU
MHL3645025DC3903
Quantity
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Square D MHL3645025DC3903 - 450A 3 Pole Molded Case Circuit Breaker
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Description
Engineered for specialized power systems, this 450A molded case circuit breaker offers robust long-time and instantaneous trip functions. It is uniquely rated for 500VDC applications while maintaining a 65kAIC interrupt capacity at 480VAC. The unit mount design allows for straightforward integration into compatible industrial enclosures and switchboards. To support complex control schemes, it includes a factory-installed auxiliary switch and undervoltage release for enhanced operational safety.Specifications
| Brand | Square D |
|---|---|
| Series | MHL |
| Amperage | 450A |
| Poles | 3 |
| Mounting Style | Unit Mount |
| Voltage | 600VAC, 500VDC |
| Phase | 3 |
| AIC Rating | 65kA @ 240VAC, 65kA @ 480VAC, 25kA @ 600VAC, 20kA @ 500VDC |
| Frame Type | M |
|---|---|
| Terminal Type | Lugs |
| For Use With | Switchboards, Motor Control Centers, Industrial Enclosures |
| Wire Gauge | (3) 3/0 AWG - 500 kcmil (Al/Cu) |
| Max Wire | 500 kcmil |
| Min Wire | 3/0 AWG |
| Trip Technology | Thermal Magnetic |
|---|---|
| Trip Function Code | LI |
| Trip Function | Long-Time, Instantaneous |
| Trip Adjustability | Fixed Thermal, Adjustable Magnetic |
| Available Options | Shunt Trip, Undervoltage Release, Alarm Switch |
|---|---|
| Accessories | Auxiliary Switch (Factory Installed), Line and Load Lugs Included |
| Standards | CSA C22.2 No. 5, UL 489 |
| Approval | CSA, UL |
| Temp Rating | 40C |
| Construction Features | High Interrupting Capacity, DC Rated, HACR Rated |
Product FAQs
9 answersWhat do the 25DC and 3903 suffixes indicate on the MHL3645025DC3903 catalog number?
The 25DC suffix designates that the breaker is rated for 500VDC applications. The 3903 suffix indicates the inclusion of factory-installed accessories, specifically a 1A/1B auxiliary switch and a 48VDC undervoltage release.
What are the wire size requirements for the MHL3645025DC3903 lugs?
The standard mechanical lugs accept three 3/0 AWG to 500 kcmil conductors per phase. They are dual-rated for both aluminum and copper (Al/Cu) wire.
Is the MHL3645025DC3903 compatible with Square D I-Line panelboards?
No. This is a unit-mount, feed-thru breaker designed for hardwired installations in switchboards, motor control centers, and industrial enclosures. It does not have the plug-on jaw connections required for I-Line panelboards.
Can the trip settings be adjusted on the MHL3645025DC3903?
The thermal-magnetic trip unit features a fixed thermal element for long-time overload protection. However, the magnetic element is adjustable, allowing you to fine-tune the instantaneous short-circuit trip threshold for your specific application.
How does the 48VDC undervoltage release enhance safety on this breaker?
The factory-installed undervoltage release automatically trips the breaker mechanism if the 48VDC control voltage drops or is lost. This prevents connected machinery from unexpectedly restarting when power is restored, requiring a manual reset by an operator.
Can the MHL3645025DC3903 be used in both AC and DC power systems?
Yes, this breaker is dual-rated for both alternating and direct current. It supports AC applications up to 600VAC with a 25kAIC rating, and DC applications up to 500VDC with a 20kAIC rating, making it suitable for specialized industrial control or DC power systems.
Is the MHL3645025DC3903 part of a legacy or current breaker series?
It belongs to the legacy Square D M-Frame molded case circuit breaker family. While newer PowerPact M-Frame models exist, this specific MHL configuration is primarily used as a direct replacement in existing legacy switchboards and motor control centers.
How are the auxiliary switch and undervoltage release wired on the MHL3645025DC3903?
The factory-installed accessories, designated by the 3903 suffix, include pigtail leads that exit the breaker housing. These leads must be hardwired into your external 48VDC control circuit for the undervoltage release and your monitoring system for the 1A/1B auxiliary contacts.
What does the LI trip function code mean on the MHL3645025DC3903?
The LI designation indicates that the thermal-magnetic trip unit provides Long-Time (L) overload protection and Instantaneous (I) short-circuit protection. It does not include Short-Time or Ground Fault protection functions.
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