
8.CAUTIONS FOR SAFETY STANDARDS RELATED TO AMPLIFIER INSTALLATION FANUC AC SERVO AMPLIFIER β series B-65232EN/03
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8.3 PROTECTION AGAINST SHOCK HAZARDS
(1) Preventing direct contact with live parts
The β series servo amplifiers, after installed, satisfy a protection
grade of IP1X (hand protection), which prevents unconscious or
inadvertent contact.
The β series servo amplifiers shall be installed within a power
magnetics cabinet. When they are powered, the power magnetics
cabinet shall be locked according to EN60204-1 so that any
person other than specialist service personnel (including those
sufficiently trained in avoiding shock hazards and qualified for
maintenance) cannot open it.
Should if a machine operator must open the power magnetics
cabinet and act on it, the operator shall be sufficiently trained for
safety beforehand, or a provision, such as a protection cover, to
keep the operator from touching the amplifiers shall be installed
in advance.
(2) Confirming electrolytic capacitor discharge
The β series amplifiers contain electrolytic capacitors with a
high capacitance in their smoothing circuits. These capacitors
remain charged for a while after the power input is shut off. If
you need to touch an amplifier, for example, for maintenance
purposes, wait for at least two minutes after the power is
switched off, or confirm safety by measuring the remaining
voltage in the DC link section and making sure that the red LED
to indicate "charge" is off.
DC voltages higher than 60V are assumed to be dangerous,
according to the relevant standards.
(3) Current leakage to a protective grounding wire
Servo motors are controlled by changing the average amplitude
and frequency of a voltage applied to their armature (winding)
using pulse width modulation.
A chopper voltage with a carrier frequency of several kHz is
applied to the motor power lines for pulse width modulation.
The motor current partly leaks to the protective grounding wire
of the motor power cord and a ground through stray capacitances
mainly between the motor armature winding and casing and
between the motor power line and a protective ground. Part of
the leakage current flows through the protective grounding wire
of the machine. This leakage current is about 0.4 to 0.5mA per
motor, measured at the commercial frequency (50/60Hz). It is
increased to 2.0mA when measured with an EN60950 compliant
measurement circuit, because the measurement circuit has a
relatively high sensitivity to higher frequency components.
If the machine is not grounded to a substantial earth ground, you
may get shocked when touching the machine. To avoid shock
hazards: