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1.3 PREVENTIVE MAINTENANCE OF SERVO AMPLIFIERS
1.3.1 Warnings, Cautions, and Notes on Preventive Maintenance of
This subsection contains the safety precautions on preventive maintenance of a servo amplifier (a generic term to refer to the
power supply, servo amplifier, spindle amplifier, and other sub modules of a motor drive unit). These precautions are classified
into "warnings", "cautions", and "notes" according to their bearing on safety. Make sure that you understand and comply with
these precautions when carrying out the maintenance work.
• Make sure that you are safely dressed and have a safe working environment when performing preventive
maintenance for a servo amplifier.
- Be dressed safely, e.g. by wearing gloves and safety shoes, to protect against injury due to an edge or protrusion and
- Have the work done by more than one person, where possible, so that immediate action can be taken if an accident
occurs when handling a motor.
- A servo amplifier and AC reactor contain heavy components. Be careful when transporting them or mounting them on
the power magnetic cabinet. Also be careful not to get your fingers caught between the power magnetics cabinet and
• Before turning on the power, check that the door of the power magnetics cabinet and all other doors.
- Ensure that the door of the power magnetics cabinet containing the servo amplifier, as well as all other doors, are
closed and locked except during maintenance work.
• When the need arises to open the door of the power magnetics cabinet, only a person trained in the maintenance of
the corresponding machine or equipment should do the task after shutting off the power supply to the power
magnetics cabinet by opening both the input circuit breaker of the power magnetics cabinet and the factory switch
used to supply power to the cabinet.
• Be careful about electric shock, fire, and other accidents.
- If the machine must be operated with the door open for adjustment or some other purpose, the operator must keep his or
her hands and tools well away from any dangerous voltages. Such work must be done only by a person trained in the
maintenance of the machine or equipment.
- Ensure that the door of the power magnetics cabinet is locked so that the door cannot be opened by anyone, except
service personnel or a qualified person trained in maintenance to prevent electric shock, when the servo amplifier is
- When the need arises for an operator to open the door of the power magnetics cabinet and perform an operation, ensure
that the operator is sufficiently educated in safety or that a protective cover is added to prevent the operator from
touching any dangerous part.
- The servo amplifier contains a large-capacity electrolytic capacitor in it and remains charged for a while after the power
is shut off. Before touching the servo amplifier for maintenance or some other purpose, measure the residual voltage of
the DC link connection using a tester and check that the red LED for indicating charging is in progress is not lit, in
order to ensure safety.
- After wiring, be sure to close the servo amplifier cover.
- A loose screw or poor connector contact can cause a motor malfunction or overheating, connection to ground, or
short-circuit. Be extremely careful with power supply lines, motor power lines, and DC link connections through which
a large electric current flows, because a loose screw or poor connector contact may lead to a fire. Tighten screws and
connectors using the specified screw tightening torque.
- The surfaces of the regenerative discharge unit and heat radiator may become very hot. Do not touch them directly by
• When operating the machine for the first time after preventive maintenance, check that the machine
operates as instructed.
- To check whether the machine operates as instructed, first specify a small value for the motor and then increase the
value gradually. If the motor operates abnormally, perform an emergency stop immediately.