MITSUBISHI MDS-B servo troubleshooting

MITSUBISHI MDS-B Series Servo Drive Maintenance and Troubleshooting Guide

System Overview and Security Upgrade Background

The Mitsubishi MDS-B series servo/spindle drive system is a comprehensive upgraded version of the MDS-A series, with core improvements aimed at meeting European safety standards (LVD) and enhancing system integration. This series consolidates the traditional rectifiers scattered in various servo and spindle drive units into independent power supply units (CV), significantly reducing heat generation and installation volume.

For engineers transitioning from the MDS-A series to the MDS-B series or facing maintenance difficulties with outdated MDS-A equipment, understanding the hardware changes, wiring differences, alarm codes, and parameter compatibility of the MDS-B series is crucial. This article will systematically outline the key points of drive replacement, fault diagnosis, and safety configuration based on the MDS-B series technical specification manual.

‍

Selection and replacement precautions for power supply unit (MDS-B-CV)

2.1 Capacity Calculation Formula

When using a power unit to drive multiple servo/spindle motors, the capacity must meet the following conditions:

Single servo shaft: power unit capacity>∑ (spindle motor output)+∑ (servo motor output)

Two or more servo axes: power unit capacity>∑ (spindle motor output)+0.7 × ∑ (servo motor output)

Note: Motor output refers to the rated output power (kW) of the motor, not the capacity of the drive unit. The spindle motor shall have a rated output of 30 minutes.

For example, if the spindle motor is 7.5kW and the three servo motors are 2kW, 1kW, and 1kW respectively, the calculated value is 7.5+0.7 × (2+1+1)=10.3kW, and an 11kW power supply unit (MDS-B-CV-110) should be selected.

2.2 Special Requirements for MDS-B-CV-370

MDS-B-CV-370 (37kW) is a newly added high-capacity model that requires the installation of external contactors and cannot share contactors with other power units. Its surge charging sequence is different from other CVs, and sharing a contactor can cause damage. The setting rules for the rotary switch (SW1) are as follows:

When using a contactor: SW1=0 or 3

When not using a contactor: SW1=1 or 5 (CV-370 is prohibited from being set to 1 or 5)

When the external emergency stop function is enabled: SW1=4 (contactor valid) or 5 (contactor invalid)

2.3 Configuration principles for multiple power supply units

When the total power exceeds 38kW, two or more power units need to be used:

The first power unit is responsible for the spindle motor power (≤ 38kW)

The second power unit is responsible for the remaining spindle power plus 0.7 times the total servo power

Key limitation: The AC reactors of each power unit must be independent and cannot be shared. Contactors can be shared in principle, but CV-370 must be independent. When connecting the busbars (L+, L -, L11, L21), they must be wired independently and cannot be short circuited or interconnected.

Main circuit wiring specifications and wire diameter selection

3.1 Power input wire diameter (reference value)

Recommended wire diameter for power unit capacity (IV/IV)

CV-37/CR-37 IV3.5SQ or HIV2SQ

CV-55/CR-55 IV5.5SQ or HIV3.5SQ

CV-75 / CR-75 HIV5.5SQ

CV-110 IV14SQ or HIV8SQ

CV-150 IV22SQ or HIV14SQ

CV-185 IV30SQ or HIV22SQ

CV-220~260 IV38SQ or HIV30SQ

CV-300~370 IV60SQ or HIV38SQ

3.2 L+, L-Bus Wire Diameter (Unified Method)

To simplify spare parts, the bus wire diameter can be uniformly selected according to the capacity of the power unit:

CV capacity wire diameter

≤37kW IV3.5SQ / HIV2SQ

55~75kW IV5.5SQ / HIV3.5SQ

110~150kW IV14SQ / HIV8SQ

185~220kW IV22SQ / HIV14SQ

260~300kW IV38SQ / HIV22SQ

370kW IV60SQ / HIV50SQ

3.3 EC Directive Compliance Wiring Points

All terminals must be crimped with insulated tubes to prevent short circuits between adjacent terminals

The protective grounding (PE) terminal must be wired separately and cannot be shared by multiple wires

The power input side needs to be equipped with non fuse circuit breakers and electromagnetic contactors that comply with EN/IEC standards

The U, V, and W output phase sequence of servo/spindle drives must strictly correspond to motor terminals A, B, and C

It is strictly prohibited to install phase capacitors or surge absorbers on the motor output line

Analysis and Handling of Common Alarm Codes

4.1 Power Supply Unit (CV) Alarm

Common Reasons and Countermeasures for Removing the Meaning of Alarm Number LED Display

63 3 Auxiliary regeneration abnormality (transistor continuously conducting) PR (power supply re powering on) Regeneration transistor failure, power supply unit needs to be replaced

65 5 Surge Relay Abnormal PR Surge Resistance Short Circuit Relay Not Closed, Check Contactor and AC Reactor

67 7 missing phase PR input power supply R/S/T, one phase is open circuit, check the power supply line

69 9 grounding fault PR motor or power line short circuit to ground, need to be checked with a megohmmeter

73 J regeneration PR (needs to be controlled for more than 15 minutes to reset). If the regeneration energy exceeds the capacity of the power unit, it is necessary to increase the regeneration resistance or reduce the acceleration and deceleration frequency