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The remaining circuits show a variety of fault circuits in the middle of the diagram that originate from the fault logic board and provide an output signal at the bottom of the diagram. You should notice that the fault output signals include overvoltage, overtempera-ture, and overcurrent. A fourth signal is identified as SSO (system status output), which in-dicates the status of the system as faulted anytime a fault has occurred. A jumper is used to set the SSO signal as an open collector output with a logic level "1" indicating the drive is ready, or as a normally closed relay indicating the drive is ready.
The input terminals at the bottom right part of the diagram are used to enable or inhibit the drive, and to select forward amplifier clamp (FAC) or reverse amplifier clamp (RAC). The inhibit signal is used as a control signal, since it inhibits the output stage of the amplifier if it is high. The FAC and RAC signals limit the current in the opposite direction to 5%.
The input signals are shown in the diagram at the upper left side. The VCS (velocity command signal) requires a +VCS and a -VCS signal to provide the differential signal.
Applications for Servo Amplifiers and Motors
You will get a better idea of how servomotors and amplifiers operate if you see some typical applications. Figure 11-90 shows an example of a servomotor used to control a press feed. In this application sheet material is fed into a press where it is cut off to length with a knife blade or sheer. The sheet material may have a logo or other advertisement that must line up registration marks with the cut-off point. In this application the speed and po-sition of the sheet material must be synchronized with the correct cut-off point. The feed-back sensor could be an encoder or resolver that is coupled with a photoelectric sensor to determine the location of the registration mark. An operator panel is provided so that the operator can jog the system for maintenance to the blades, or when loading a new roll of material. The operator panel could also be used to call up parameters for the drive that cor-respond to each type of material that is used. The system could also be integrated with a programmable controller or other type of controller and the operator panel could be used to select the correct cutoff points for each type of material or product that is run.
FIGURE 11-89 Diagram of a pulse-width modulator (PWM) amplifier with a brush-type DC servomotor.
FIGURE 11-90 Appli-cation of a servomotor controlling the speed of material as it enters a press for cutting pieces to size.
