Solving USB communications problems when the motor power is enabled
Problem
I lose USB communications when I enable the motor power. What can I do to minimize this problem?
Solutions
USB communication problems when the motor is enabled can be minimized with the following actions:
- Ensure the driver, the power supplies, the motor and the computer are well grounded to the installation earth. Provide a short, good quality connection.
- Ensure that the driver PE terminal (typically mounting holes) is connected to earth of the installation and to the motor housing.
- If possible connect the driver GND (supply negative) to earth near the supply terminal.
- Use motor power choke as recommended in the product manuals (such as Jupiter or Pluto). All the motor phases should pass through the ferrite except the earth line. This solution has proven very effective in high voltage - high current applications.
- Use USB cables as short as possible.
- If none of these solutions work, use a USB port isolator. Next parts have been tested and provide a very reliable connection in high power applications. Actually, they improve user safety by separating driver and computer board with a reinforced isolation:
Part Number | Manufacturer | Description | Image | Suppliers |
B+B SMARTWORX | 2kV port isolator with power supply | |||
B+B SMARTWORX | 4kV rugged industrial USB isolator |
Technical discussion
The servo drive and motor system cause electrical noise when switching. To maximize the power efficiency of the driver, fast on-off transitions are needed. Although INGENIA optimizes the drivers for the best tradeoff of efficiency and performance, this noise could be coupled to the USB port and cause communication problems.
Due to the inherent limitations of the USB interface for industrial or intrinsically noisy applications, it is always suggested to use CANOpen, EtherCAT or RS485 interfaces to interface drivers working at currents > 10 A or voltages > 60 V.
Adding a ferrite choke on the motor lines minimize the ground transient currents during PWM switching.
Adding an electrical isolation on the USB port cuts the ground loops and minimizes conducted EMI. It also adds an additional safety line between the power application and the user.
Although not currently available, we will add USB rugged isolation in next product generations of high power drivers such as Jupiter.
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