3-32
D No-fuse Breakers (NFB)
When selecting no-fuse breakers, take into consideration the maximum output current and the inrush
current.
Maximum input current:
The momentary maximum output for a Servo Driver is approximately three times that of the rated out-
put, and a maximum output of three seconds can be executed. Therefore, select no-fuse breakers with
an operating time of at least five seconds at 300% of the rated maximum output. General-purpose and
low-speed no-fuse breakers are generally suitable. The table in 3-2-3 Terminal Block Wiring shows the
rated power supply input currents for each Servomotor. Select a no-fuse-breaker with a rated current
greater than the total effective load current (when multiple Servomotors are used). When making the
selection, add in the current consumption of other controllers, and so on.
Servo Driver inrush current:
With low-speed no-fuse breakers, an inrush current 10 times the rated current flows for 0.02 second.
For a simultaneous inrush for multiple Servo Drivers, select a no-fuse-breaker with a 20-ms allowable
current greater than the total inrush current shown in the following table for the applicable Servomotor
models.
Servo Driver
Inrush current (Ao-p)
Control-circuit power supply Main-circuit power supply
R88D-WTA3HL to -WT02HL 30 90
R88D-WTA3H to -WT04H 35 90
R88D-WT05H to -WT10H 60 130
R88D-WT15H 60 130
R88D-WT20H/-WT30H 60 140
R88D-WT50H 60 140
R88D-WT60H 65 140
R88D-WT75H 65 140
R88D-WT150H 65 140
D Surge Absorbers
Use surge absorbers to absorb surges from power supply input lines due to lightning, abnormal volt-
ages, etc. When selecting surge absorbers, take into account the varistor voltage, the amount of surge
immunity, and the amount of energy resistance. The surge absorbers shown in the following table are
recommended.
Maker Model Max. limit
voltage
Surge
immunity
Type Remarks
Okaya Electric
RSASV-781BYZ-2
783 V 1,000 A
Block
Between power supply lines
Industries Co., Ltd.
RSASV-781BXZ-4
783 V 1,000 A Between power supply line
grounds
Note 1. Refer to the manufacturers’ documentation for operating details.
Note 2. The surge immunity is for a standard impulse current of 8/20 µs. If pulses are wide, either decrease the
current or change to a larger-capacity surge absorber.
System Design and Installation
Chapter 3
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