Beckhoff AX8000 servo installation fuse selection

AX8620 X01 (10 pins) single-phase to L1/N, three-phase to L1/L2/L3/PE; 24V control power is connected to 24V/GND.

AX8640 X01 (4-pin)+X02 (6-pin) X01 connected to three-phase main power supply, X02 connected to 24V control power and external braking resistor.

AX8600 X01 (7-pin) DC+/DC - connected to DC bus, 24V/GND connected to control power.

AX85xx X01 terminal block (L1/L2/L3/PE) with a maximum wire diameter of 35 mm ² (AWG 2) and a torque of 2.5-4.5 Nm.

Key warning: Before connecting the external braking resistor, the short circuiting piece between Rbint+and Rb on the power module terminal must be removed, otherwise the external braking resistor cannot be correctly switched and the system will report an error and stop. The PE wire of the braking resistor must be connected through the PE point of the X02 terminal.

3.2 Implementation of Separation between Protective Grounding (PE) and Functional Grounding (FE)

The AX8000 has a very strict distinction between grounding:

Protective grounding (PE): Connect a cable with a ring terminal of ≥ 10 mm ² to the central grounding point of the control cabinet mounting board through the grounding bolt on the left side of the power module to prevent electric shock. Optionally, attach a second PE wire to the grounding bolt on the right side of the last module.

Functional Grounding (FE): Low impedance connection between modules is achieved through Grounding Hanger, ensuring effective discharge of high-frequency EMC interference. The fixing nut torque of the grounding hanging ring is 2.7 Nm, and the use of spring washers is strictly prohibited.

EMC rating and cable length:

Only use Beckhoff original shielded motor cables.

When there is no reactor, the maximum length of a single motor cable is 25 meters, and the total length of the system is ≤ 300 meters.

After installing the AX2090-ND80 reactor, a single cable can be extended up to 100 meters, and the total length of the system is ≤ 500 meters.

To meet the C2 EMC limit (residential and light industrial environments), additional AX2090-NF80 series filters need to be installed and matched with corresponding reactors.

3.3 Calculation of DC bus capacitance and charging time

The AX8000 adopts a common DC bus architecture, and the DC bus capacitors of all axis modules are uniformly charged by the power module. The maximum rechargeable capacitance value of the power module when first powered on varies depending on the voltage level:

Power module 230 VAC 400 VAC 480 VAC

AX8620 25,000 μF 8,500 μF 6,000 μF

AX8640 - 13,500 μF -

AX8540 - 23,000 μF 13,000 μF

Engineering example: If the system includes 1 x AX8640 (625 μ F)+10 x AX8206 (10 x 135 μ F=1350 μ F)+1 x AX8810 (1755 μ F), the total capacitance is 3730 μ F, which is lower than the upper limit of 13500 μ F of AX8640 at 400V, the design is safe. The charging time is about 5 × RC. Taking AX8620 full load capacitor (8500 μ F) as an example, the charging time is about 1.4 seconds.

Chapter 4: UL/CE Compliance Fuse Protection Selection Strategy

4.1 Circuit breaking schemes under different SCCR levels

AX8000 requires the selection of external fuses based on the short-circuit current rating (SCCR) of the installation site to comply with UL 508A or IEC 60269 requirements.

CE compliance (gG fuses or C-characteristic circuit breakers):

Maximum SCCR specification for power module fuse

AX8620 gG (A) or C characteristic circuit breaker, ≤ 25 A 5 kA

AX8640 gG (A) or C characteristic circuit breaker, ≤ 50 A 5 kA

AX8525/AX8540 gG (A) or C characteristic circuit breaker, ≤ 100 A 10 kA

UL compliant (Class J fuses):

Use UL certified Class J fuses and strictly follow the replacement rules in section SB4.2.3 of UL 508A.

If a 65 kA SCCR is required, semiconductor fuses (aR type) can be connected in series:

AX8620：Bussmann FWC-32A10F（32 A）

AX8640：Bussmann FWP-63A22F（63 A）

Semiconductor fuses are only used for short-circuit protection and must be connected in series with Class J fuses to achieve line protection.

4.2 Application oriented setting of fuse current

It is not recommended to directly select based on the maximum rated current of the power module, but should be calculated based on the sum of steady-state currents (I ₀) of all servo motors multiplied by the simultaneous coefficient.

Example: In a certain three-axis handling system, the motor currents of each axis are 6.90 A, 1.95 A, and 0.85 A, with a total current of 9.70 A. Taking a simultaneous coefficient of 0.7, the equivalent current is 6.8 A. Therefore, a 10 A fuse can be selected, which is much lower than the upper limit of 25 A of the power module, and is both safe and economical.

Chapter 5: Status Display and Fault Diagnosis

5.1 Interpretation of 7-segment display screen status

AX8000 modules provide real-time feedback on their status through a high brightness 7-segment LED display screen

Power module:

E (green constantly on): EtherCAT master station is active and configured for activation.

P (green flashing): The DC bus is charging and discharging (flash>48V, slow flash ≤ 48V).

P (red): Fault.

Axis module:

A (green constantly on): The shaft is enabled and there are no faults.

A (flashing red and green alternately): The axis is executing a fault response.