IS200BICLH1B通用电气卡件,工业自动化卡件
.。每两个RTD共享一个共同的回报。469 RTD电路补偿导线电阻，前提是三根导线的长度相同。引线电阻不应超过25Ω 铂/镍型RTD或3Ω 铜型RTD的每根引线。应使用屏蔽电缆，以防止工业环境中的噪声拾取。RTD电缆应靠近接地金属外壳，远离高电磁或无线电干扰区域。RTD引线不应与大电流载电线相邻或在同一导管中。图2-18：RTD接线重要事项：RTD电路与模拟输入电路和模拟输出电路作为一组隔离。三个电路只能使用一个接地参考。相对于469安全接地，Transorbs将此隔离限制在±36 V。电机起动器3线屏蔽电缆电机起动器RTD端子电机最大总导线电阻25欧姆（铂和镍RTD）3欧姆（铜RTD）电机起动器中的电机RTD端子在电机定子或轴承806819A5.CDR B1 A1 A2 A3热补偿回路屏蔽底盘接地RTD传感RTD#1 469继电器注释2-16 469电机管理继电器GE Power Management 2.2电气2安装2 b）减少RTD引线编号应用469要求从每个RTD带回三根引线：热引线、回流引线和补偿引线。这可能相当昂贵。然而，对于第一个RTD，可以将所需的引线数量减少到3根，对于每个连续的RTD，可以减少到1根。有关此应用的接线配置，请参阅下图。图2–19：减少布线电阻每个电阻式温度检测器的火线必须照常运行。然而，补偿和返回导线只需用于第一个RTD。在电机RTD接线盒上，RTD回路导线必须与尽可能短的跳线一起跨接。补偿导线必须在469处跨接在一起。注意，在每个RTD上产生的误差等于RTD回路跳线两端的电压降。该误差随着每个连续RTD的增加而增加。VRTD1=VRTD1 VRTD2=VRTD2+VJ3 VRTD3=VRTD3+VJ3+VJ4 VRTD4=VRTD4+VJ3+VJ4+VJ5等……此错误直接取决于跳线所用导线的长度和规格，以及不良连接导致的任何错误。对于10以外的RTD类型Ω 铜，跳线引入的误差可以忽略不计。这种RTD接线技术降低了接线成本，但必须注意以下缺点：1。由于导线和连接电阻，温度读数会有误差。不建议在10Ω 铜RTD。2.如果通向469或任何跳线的RTD回路断开，则断开点的所有RTD读数将为开路。3.如果补偿导线或任何跳线断开，断开点的所有RTD将在没有任何导线补偿的情况下工作。GE Power Management 469电机管理 Every two RTDs shares a common return. The 469 RTD circuitry compensates for lead resistance, provided that each of the three leads is the same length. Lead resistance should not exceed 25 Ω per lead for platinum/nickel type RTDs or 3 Ω per lead for copper type RTDs. Shielded cable should be used to prevent noise pickup in the industrial environment. RTD cables should be kept close to grounded metal casings and away from areas of high electromagnetic or radio interference. RTD leads should not be run adjacent to or in the same conduit as high current carrying wires. Figure 2–18: RTD WIRING IMPORTANT: The RTD circuitry is isolated as a group with the Analog Input circuitry and the Analog Output circuitry. Only one ground reference should be used for the three circuits. Transorbs limit this isolation to ±36 V with respect to the 469 safety ground. MOTOR STARTER 3 WIRE SHIELDED CABLE MOTOR RTD TERMINALS IN MOTOR STARTER RTD TERMINALS AT MOTOR Maximum total lead resistance 25 ohms (Platinum & Nickel RTDs) 3 ohms (Copper RTDs) Route cable in separate conduit from current carrying conductors RTD IN MOTOR STATOR OR BEARING 806819A5.CDR B1 A1 A2 A3 HOT COMPENSATION RETURN SHIELD CHASSIS GROUND RTD SENSING RTD #1 469 RELAY NOTE 2-16 469 Motor Management Relay GE Power Management 2.2 ELECTRICAL 2 INSTALLATION 2 b) REDUCED RTD LEAD NUMBER APPLICATION The 469 requires three leads to be brought back from each RTD: Hot, Return and Compensation. This can be quite expensive. It is however possible to reduce the number of leads required to 3 for the first RTD and 1 for each successive RTD. Refer to the figure below for wiring configuration for this application. Figure 2–19: REDUCED WIRING RTDS The Hot line would have to be run as usual for each RTD. The Compensation and Return leads, however, need only be run for the first RTD. At the motor RTD terminal box, the RTD Return leads must be jumpered together with as short as possible jumpers. The Compensation leads must be jumpered together at the 469. Note that an error is produced on each RTD equal to the voltage drop across the jumper on the RTD return. This error increases with each successive RTD added. VRTD1 = VRTD1 VRTD2 = VRTD2 + VJ3 VRTD3 = VRTD3 + VJ3 + VJ4 VRTD4 = VRTD4 + VJ3+ VJ4 + VJ5, etc.... This error is directly dependent on the length and gauge of the wire used for the jumpers and any error introduced by a poor connection. For RTD types other than 10 Ω Copper, the error introduced by the jumpers is negligible. This RTD wiring technique reduces the cost of wiring, however, the following disadvantages must be noted: 1. There will be an error in temperature readings due to lead and connection resistances. This technique is NOT recommended for 10 Ω Copper RTDs. 2. If the RTD Return lead to the 469 or any of the jumpers break, all RTDs from the point of the break will read open. 3. If the Compensation lead or any of the jumpers break, all RTDs from the point of the break will function without any lead compensation. GE Power Management 469 Motor Management
