TJ2-300/200 Series Electromagnetic Drum Brakes

The TJ2-300/200 series electromagnetic drum brake is a normally-closed, spring-applied, AC electromagnetic-released braking device designed for heavy-duty lifting and transport machinery. It is exclusively matched with the MZD1-200 AC electromagnetic brake (single-phase AC 380V/50Hz) and complies with industrial standards for electromagnetic brakes. Its core function is to control the lifting speed of objects and absorb the inertia of moving/rotating mechanisms, making it widely used in non-explosive environments such as cranes, hoists, metallurgical auxiliary equipment, and construction machinery.

Core Technical Specifications

Parameter	Standard Value	Notes
Brake Type	Normally-closed electromagnetic drum brake (spring braking, electromagnetic release)	Fail-safe: Maintains braking on power loss
Applicable Brake Drum Diameter	300 mm	Matches heavy-duty machinery drum specifications
Rated Braking Torque	- JC=25%/40% (intermittent operation): 500 N·m- JC=100% (continuous operation): 200 N·m	JC = duty cycle; torque adjusts with operation frequency
Matching Electromagnet Model	MZD1-200	Single-phase AC 380V/50Hz; electromagnetic torque adapts to brake demand
Brake Shoe Clearance (Retreat Distance)	- Normal: 0.7 mm- Maximum: 1.0 mm	Ensures no friction between shoe and drum during release
Adjustment Rod Stroke	3–4.4 mm	Used to fine-tune brake shoe clearance and braking torque
Friction Lining Material	Asbestos brake band (replaceable)	High friction coefficient; ensures stable braking force (Summary 1, 4)
Working Conditions	- Ambient Temperature: -20℃～+50℃- Relative Humidity: ≤90%- No explosive/corrosive gases or conductive dust	Complies with general industrial environment requirements (Summary 3)
Key Installation Dimensions (mm)	- Brake shoe width: 140- Overall length: 825- Mounting center distances (A/A1/A2): 519/625/80	Standardized for universal mounting on heavy machinery (Summary 4)
Weight (w/o Electromagnet)	~55 kg	Robust structure for heavy-duty operation

Key Structural & Functional Features

Fail-Safe Normally-Closed MechanismAdopts the core logic of "spring braking + electromagnetic release" (Summaries 1, 3, 4). When the MZD1-200 electromagnet is de-energized, the pre-compressed main spring drives the brake shoes (with asbestos bands) to clamp the 300 mm-diameter drum tightly, generating 200–500 N·m of braking torque to prevent equipment slipping or object falling. When the electromagnet is energized, it generates a magnetic force to pull the lever mechanism, overcoming the spring force and separating the shoes from the drum-allowing the machinery to run normally.

Reliable Electromagnetic ActuationThe matched MZD1-200 AC electromagnet features low electromagnetic noise and stable suction force (Summary 3). It operates at a standard industrial voltage (single-phase AC 380V), eliminating the need for additional voltage conversion devices. The electromagnet's stop block is closely aligned with the adjustment rod's top, ensuring precise control of the brake's release stroke and avoiding excessive wear caused by misalignment.

Replaceable Asbestos Friction LiningsThe brake shoes are equipped with riveted asbestos brake bands (Summaries 1, 4)-a material with a high friction coefficient that ensures consistent braking performance even under heavy loads. When the lining is worn (typically when thickness is ≤3 mm), it can be independently replaced without disassembling the entire brake body, reducing maintenance time and costs.

Adjustable Clearance & Torque

Clearance Adjustment: The adjustment rod (stroke 3–4.4 mm) allows operators to fine-tune the shoe-drum clearance to the standard 0.7–1.0 mm range, avoiding abnormal noise or reduced braking efficiency caused by excessive/insufficient clearance.

Torque Adjustment: By adjusting the main spring's compression length, the braking torque can be adapted to different load demands (200 N·m for continuous operation, 500 N·m for intermittent heavy loads), enhancing the brake's versatility.

Robust Structural DesignThe brake lever, vertical plate frame, and base are all made of high-strength steel (Summary 4), withstanding the impact force generated during emergency braking. Connections between components (e.g., vertical plate frame and base, brake shoe and vertical plate frame) use shaft pins for flexible rotation, ensuring smooth brake actuation without jamming.

Working Principle

The TJ2-300/200 operates based on the coordination of electromagnetic force and mechanical spring force, with clear division of labor between the MZD1-200 electromagnet and internal components:

Brake Application (Power-Off State: Stopping/Emergency)When the control system cuts off power to the MZD1-200 electromagnet, the electromagnet loses suction. The pre-compressed main spring rebounds instantly, pulling the vertical plate frame and brake shoes to swing inward. The asbestos friction linings clamp the rotating 300 mm drum tightly, converting the machinery's kinetic energy into heat (dissipated into the air) through friction. The braking torque (200–500 N·m) quickly decelerates the drum, stopping the load or preventing it from falling-critical for lifting machinery safety.

Brake Release (Power-On State: Operation)When the machinery needs to run (e.g., lifting or lowering objects), the electromagnet is energized. It generates a strong magnetic force to attract the stop block, driving the adjustment rod and lever mechanism to move. This overcomes the main spring's pre-tightening force, pushing the brake shoes outward to separate from the drum (clearance 0.7–1.0 mm). At this point, the drum can rotate freely, and the machinery operates normally.

Typical Applications

Aligned with TJ2 series application scenarios (Summaries 1, 3, 4), the TJ2-300/200 is mainly used in heavy-duty lifting and transport scenarios:

Lifting Machinery

Bridge cranes, gantry cranes, and jib cranes: Provides braking for the lifting mechanism, ensuring stable control of heavy loads (e.g., steel plates, construction materials) during ascent/descent and safe parking when suspended.

Electric hoists and winches: The high braking torque (up to 500 N·m) handles the inertia of heavy loads during sudden stops, preventing load slipping.

Metallurgical & Construction Machinery

Metallurgical auxiliary equipment (blast furnace charging machines, rolling mill feeders): Adapts to high-temperature workshop environments (-20℃～+50℃) and ensures stable braking during material transport.

Construction site tower cranes and concrete mixers: The robust steel structure resists vibration and impact, ensuring reliable performance in harsh construction environments.

Transport Machinery

Heavy-duty rail-guided vehicles (RGVs) and material transfer trolleys: Provides parking braking to prevent movement during loading/unloading, and emergency braking to handle unexpected situations.

Installation & Maintenance Guidelines

Installation Key Points

Drum Preparation: Ensure the 300 mm brake drum is dynamically and statically balanced (Summary 1), with surface roughness ≤Ra 1.6 μm and hardness ≥HB 280. The drum's runout, out-of-roundness, and taper must not exceed 0.0005D (D=300 mm, i.e., ≤0.15 mm).

Alignment Requirement: The center line of the two brake shoes must pass through the drum's center, with a deviation ≤0.3 mm (Summary 1). Use a level to verify the brake base's flatness (error ≤0.5 mm/m) to avoid uneven lining wear.

Electromagnet Mounting: Install the MZD1-200 electromagnet on the vertical plate frame, ensuring its stop block is aligned with the adjustment rod's top (gap ≤0.5 mm). Connect the electromagnet to a single-phase AC 380V power supply, and verify grounding (resistance ≤4 Ω) for electrical safety.

Clearance & Torque Calibration: After installation, use the adjustment rod to set the shoe-drum clearance to 0.7–1.0 mm. Adjust the main spring's compression length to match the required braking torque (e.g., 500 N·m for intermittent heavy loads).

Maintenance Schedule

Cycle	Tasks	Details
Daily	Visual Inspection	Check asbestos lining wear (replace if thickness ≤3 mm), drum surface (no oil stains/scratches), and electromagnet wiring (no looseness).
Weekly	Clearance & Spring Check	Verify shoe-drum clearance (adjust via adjustment rod if deviated); check main spring for deformation (replace if elasticity decreases).
Monthly	Electromagnet Maintenance	Clean the electromagnet's iron core with a dry cloth to remove dust; test the electromagnet's suction force (ensure it can fully release the brake).
Quarterly	Fastener & Shaft Pin Lubrication	Retighten base and electromagnet bolts (torque: 40–45 N·m); apply lithium-based grease to shaft pins (between vertical plate frame and base) to prevent rust.
Annually	Comprehensive Overhaul	Test braking torque (ensure it meets 200–500 N·m range); re-machine the drum if runout exceeds 0.15 mm; replace aging electromagnet coils if suction is weak.

Common Faults & Solutions

Fault Phenomenon	Possible Causes	Solutions
Electromagnet energized but brake not released	Adjustment rod misalignment; electromagnet suction weak	Realign the adjustment rod to align with the electromagnet's stop block; replace the electromagnet coil if suction is insufficient.
Insufficient braking torque	Lining wear; main spring fatigue	Replace the asbestos brake band; adjust the main spring's compression length or replace the spring.
Abnormal noise during braking	Uneven shoe-drum clearance; drum runout excessive	Re-adjust clearance to 0.7–1.0 mm; re-machine the drum if runout >0.15 mm.
Electromagnet overheating	Exceeded duty cycle (JC>100%); coil short circuit	Reduce brake actuation frequency; test coil insulation (≥1 MΩ) and replace if s

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