REXROTH MKD Explosion proof Synchronous Motor Application Guide

REXROTH MKD Explosion proof Synchronous Motor Application Guide

1. Product Overview and Applicable Standards

The Bosch Rexroth MKD series synchronous motor is a servo drive solution designed specifically for potentially explosive environments, meeting the requirements of Class II, Class 3 equipment in the ATEX Directive (94/9/EC), and suitable for gas (G) and dust (D) environments. This series of motors provides efficient and reliable power output, with a maximum torque of up to 18 Nm. It comes standard with a rotary transformer encoder and can be optionally equipped with a multi turn absolute encoder, a holding brake, or a keyway output shaft.

The MKD explosion-proof motor adopts "nA" type explosion-proof protection (non spark equipment), with a maximum surface temperature limit of 155 ° C. It is suitable for situations where explosive environments do not occur during normal operation, or where they can be quickly eliminated through ventilation and monitoring even if they do occur. The protection level of the motor housing is IP65, with good dust and water spray resistance, suitable for typical application scenarios such as industrial automation, packaging machinery, printing equipment, food processing and handling systems.

2. Safety regulations and usage precautions

Safety is always the primary consideration when using electrical equipment in explosive hazardous environments. MKD motors strictly comply with international standards such as ATEX and EN 50021, and users must fully adhere to the following safety principles in design, installation, and operation:

2.1 Expected and Unintended Uses

The motor is only suitable for the application scenarios and environmental conditions specified in the technical documentation. Prohibited from use in the following situations:

The environmental requirements are higher than the explosion-proof level indicated on the motor nameplate;

Underwater, extreme temperature or frequent temperature fluctuations;

Other application areas not explicitly approved by Rexroth.

2.2 Electrical Safety and Grounding Requirements

The motor must be reliably grounded through motor cables and independent grounding wires (with a minimum cross-sectional area of 4 mm ²) to prevent leakage and spark risks. All electrical connections must be made in non explosive areas, and it is strictly prohibited to plug or unplug connectors while they are live or under load.

2.3 Protective measures

Mechanical hazard: Measures such as safety fences, light curtains, and emergency stop switches must be taken to prevent personnel from entering the hazardous area.

Hot surface protection: The motor casing may reach high temperatures during operation, and it needs to be cooled to a safe temperature (up to 140 minutes) before it can be touched after shutdown.

Magnetic field protection: The magnetic field generated by the motor may affect pacemakers, metal implants, or hearing aids, and relevant personnel must stay away from the work area.

2.4 Specific requirements for explosion-proof environment

In explosive dust environments, it is necessary to prevent dust from accumulating on the motor casing to avoid affecting heat dissipation and causing temperature rise. The installation position of the motor should be easy to clean, and the ignition temperature of the dust must be much higher than the maximum surface temperature of the motor (155 ° C).

3. Analysis of motor model and technical parameters

The MKD series covers four basic models: MKD025, MKD041, MKD071, and MKD090, corresponding to different machine base sizes and power levels. Under each model, there are multiple winding codes and length specifications to meet different torque, speed, and inertia requirements.

3.1 Basic Technical Parameter Description

Continuous stalling torque (M ₐ N): The torque that the motor can continuously output at zero speed.

Peak current (I ₘₐₓ): The maximum phase current that a motor can withstand in a short period of time.

Torque constant (K ₘ): The torque value generated per unit current, used in control system design.

Thermal time constant (T ₜₕ): The time required for the temperature of the motor casing to rise to 63% of the steady-state value, which affects the heat dissipation design and operating cycle.

Rated data: including rated speed, torque, current, power, and voltage, defined based on S1 continuous working system or S6 intermittent working system (25% load duration rate).

3.2 Performance Curve and Operating Mode

The motor provides speed torque curves under two temperature rise parameters:

60K curve: insulation structure test based on winding temperature rise of 60K and ambient temperature of about 45 ° C.

100K curve: Non insulated structure test based on winding temperature rise of 100K and ambient temperature of about 40 ° C.

It is recommended to prioritize using 60K data in precision systems to reduce the impact of thermal expansion on positioning accuracy. The curve graph also includes a constant power zone limited by the DC bus voltage, S1 continuous working zone, and S6 intermittent working zone, providing users with intuitive basis for selection.

3.3 Axle Load and Bearing Life