[求助]一篇数控方面的翻译那位大侠能帮小弟解决一下，不胜感激（毕业设计的文献翻译

hero631 · 发表于 2007-3-14 17:03:00

Avoiding the Pitfalls of Powering CNC Equipment————The susceptibility of a CNC machine to different sources of noise and stray currents depends on its design, but grounding, bonding, and shielding play a vital role                                                                   （By Thomas S. Key, EPRI）  As the use of CNC machines becomes more prevalent, minimizing production downtime, product loss, and expensive repair bills becomes increasingly important. Good practices for installation, powering and grounding, and maintenance procedures are all required to prevent malfunction, degradation, and damage to electronics.Today's electronically controlled CNC machine requires a common signal reference ground for its logical circuits to operate reliably. Upsets related to grounding and ground references are usually attributed to noise or stray currents that find their way into logic circuits. A common wiring-related source is the inductive coupling of noise currents into wires of control and power circuits run in the same raceway or placed in close proximity to each other inside a CNC machine. Additional sources include contactors, relays, solenoids, and motor drives that are internal to the CNC machine. (For more sources, see sidebar "Noise Sources and Coupling Modes" on page 28.)The susceptibility of a CNC machine to different sources of noise and stray currents will depend on its installation as well as how the manufacturer designed the machine. Grounding, bonding, and shielding also play a role, as do the use of certain types of communication cables that are more susceptible to high-frequency noise or stray ground currents.  Problem areas. Most machine shops are supplied by either a 3-phase, 4-wire grounded service (at either 208Y/120V or 480Y/277V) or a 3-phase ungrounded service (at 480V delta or 240V delta). Both services require a grounding electrode conductor to reference the electrical power system to the building grounding electrode system, which consists of all available earth electrodes (building steel, metal water pipes, buried ground rings, and ground rods).The intent of the grounding electrode conductor and grounding electrode system is three-fold:• To provide a low-impedance path to earth for lightning surge or electrical fault currents.• To provide a low-impedance fault return path hack to the source in order to trip the breaker.• To reference the building electrical system to its surroundings. In other words, minimize voltage differences between exposed metal parts of the power system, including connected equipment and the surrounding parts of the building.            Typically, a CNC machine's signal reference is a common wire of its computer logic power supply connected to the machine's ground plate. The ground plate, in turn, is bonded to the machine's enclosure, equipment grounding conductor, or conduit — and, subsequently, to the building grounding electrode system. So, the equipment ground establishes the local signal reference both within the CNC machine and for any remotely connected devices (Fig. 1. on page 26).          CNC machines contained in a single cabinet with good bonding, grounding, and shielding should be relatively immune to noise. However, those machines with remote controllers or data links may be quite susceptible to noise or stray currents. That's because the other area of the factory will also have a signal reference ground. These different reference ground points may increase a CNC machine's sensitivity to power disturbances (Fig. 2 on page 26).

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[求助]一篇数控方面的翻译那位大侠能帮小弟解决一下，不胜感激（毕业设计的文献翻译

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