汽车测试：您要走哪条路？

Introduction

通用汽车公司艾里逊变速箱是全球领先的商用车自动变速箱、混合动力推进系统以及相关零部件和服务的设计、制造和销售商，产品广泛应用于公路卡车、公共汽车、非公路设备和军用车辆。 艾里逊变速箱公司隶属于通用汽车动力总成部门，除位于印第安纳州印第安纳波利斯的总部外，还在荷兰、日本、中国、新加坡和巴西设有国际地区办事处，并通过拥有 1500 名成员的分销商和经销商网络在 80 多个国家开展业务。

全面电机维护 (TMM) 概念是一项从电机库存和交付到电机测试和可靠性的日常策略。

 

优质网络计划维护

艾里逊变速箱遵循通用汽车北美公司 (GMNA) 联合汽车工人质量网络计划维护 (QNPM) 流程。 该计划提供了一个共同的流程和一致的结构，以确保设备、机械、工具和设施以安全的方式运行，并能以具有竞争力的方式生产出满足客户需求的产品。 有一些操作原则确定了 QNPM 共同流程的基本方向。 在整个规划和实施过程中都参考了这些原则，以确保所有活动都以实现以下目标为重 点：

在全球移动网络、部门和工厂层面提供持续支持和指导

确保生产部门是计划维护的所有者和倡导者。

为所有员工创造参与过程的机会

落实操作员参与理念

进行主动维护。

在安全、质量、产量和成本方面达到世界一流水平。

支持持续改进

 

计划维护中有十二个相互依存的要素，它们是成功维护过程不可或缺的组成部分。 每个要素都对其他要素起到促进和支持作用。 这些相关要素共同构成了计划维护流程的基础（图 1）：

人员参与和组织

财务监督和控制

备件供应

培训

通信

故障应急响应

定期维护

建筑工程

维护工具和设备的可用性

可靠性和可维护性

内务和清洁

生产维护合作伙伴

 

发动机供应商合作伙伴计划

商品管理 “是艾里逊变速箱与主要电机供应商合作计划的术语。 实现的一些主要功能包括提高服务质量、降低运营和库存成本。 储存的艾里逊备用库存电机存放在供应商的仓库中。 随后，供应商每月与埃里森人员会面，报告采购、更换、交货时间以及硬性和软性节约情况（图 2）。

通过将电机电路分析 (MCA) 作为电机项目中的一项技术（红外线、振动、超声波等），埃里森可以更准确地满足客户的需求和期望。 在将电机拆卸并送往供应商的电机维修车间之前，即使经验有限，也能在几分钟内对电机进行测试。 在评估电机时，内部 MCA 测试和供应商参与的根本原因分析发挥着重要作用。 电机维修完成后，供应商会向艾里逊提供一份维修和维修原因报告。 如果故障是由污染引起的，电机车间供应商会收集定子绕组内的污染样本，并将其交给艾里逊技术部门进行实验室分析。 所有这些信息都有助于公司解决电机问题和故障的根本原因。

在一个部门，一个伺服电机在 10 个月内发生了 17 次故障。 该供应商被要求协助确定根本原因和纠正行动计划。 电机位于潮湿恶劣的地方，那里有大量冷却液。 供应商建议在电机轴上安装一个吊环，并采用特殊的密封工艺，以防止电机过早失效。 该公司的电机供应商用黄色条纹标明了这些改装，以示电机经过改装（图 3）。 迄今为止，该伺服电机还没有出现过因污染而导致绕组故障的情况。

事实证明，与汽车修理厂的合作非常有效。 艾里逊可以每周 7 天、每天 24 小时拨打电话，以便在两小时内将储存的电机运送到码头（图 4）。 响应时间对于规划生产计划非常宝贵。 艾里逊还能接触到电机供应商的主题专家。 因此，我们将供应商视为可靠性工具箱的一部分。 最终，电机车间供应商要对艾里逊变速箱的商品管理团队负责，该团队由 QNPM 代表、电机车间和可靠性部门的电工、备件团队、维护主管以及财务部门的人员组成。

MCA 概览

艾里逊变速箱公司的电机项目是运营中的重要组成部分。 有了 MCA，可以对出现问题的电机进行测试以确认故障，然后将其拆卸并送出维修。 如果找不到电机问题，电工会帮助维修技术人员找到根本原因。 对于难以安装的电机，在请机器维修人员安装之前要进行测试。 供应商仓库中的电机每季度进行一次 MCA 测试。 由于电机故障的反复出现，已经确定了一些路线，作为 MCA 流程的一部分，每月都会对这些电机进行测试和趋势分析。 在重建泵之前，要对带泵的电机进行测试，以确定更换电机泵组合是否比重建更经济。 2002 年期间维修或更换的各类电机的细目见图 4。

QNPM 共同维护冠军

艾里逊 UAW 联合冠军 Delbert Chafey 说：”使用电机电路分析工具使我们在制造服务领域的业务方式发生了巨大变化，并扭转了因错误判断而造成的损失，例如，判定电机坏了并简单地更换它。我们的商品经理订购更换电机的数量大幅下降，因此，制造服务机构可以提供更长的机器正常运行时间。其结果是以更具竞争力的价格提供了更多的零部件，扩大了技术基础，更好地利用了（故障根源分析）RCFA，并为我们的技术团队带来了更大的信心。更长的正常运行时间 + 节约 + 训练有素的技工 + 技术工具箱中的好工具 = 成功。完美的组合！”

艾里逊变速箱 QNPM 联合冠军 Terry Bowen 参加了 2001 年通用汽车 QNPM 研讨会上的电机电路分析研讨会，他认为公司可以从技术部门实施的 MCA 计划中获益。 2001 年 5 月，在汽车修理厂的一次演讲中，Bowen 承认了该工具的重要性，并表示艾里逊公司已经购买了三个。

在购买 ALL-TEST Pro™ 电机电路分析仪之前，分析电机需要大量的猜测。 有时，在没有对问题进行全面诊断的情况下，电机就会被送往供应商处。 在供应商进行测试后，报告会显示 “未发现问题”。现在，随着 MCA 计划的实施，Allison 发现机器的正常运行时间延长了，”未发现问题 “的报告也减少了。

约有 50 名埃里森技工正在通过戴夫-汉弗莱（Dave Humphrey）教授的八小时内部课程，接受有关应用和使用 MCA 仪器的培训。 参与培训的工种包括电工、动力室固定工程师、空调和维修主管。

电机问题

使用 MCA 发现的电机定子故障包括匝间故障、相间故障、线圈间故障、接地故障和转子故障。 转子故障在 4160 伏而不是 480 伏的电机中更为常见，主要表现为转子杆断裂、偏心和铸件空洞。 通过查看 ALL-TEST ProTM MCA 设备上的相位角和电流频率可以识别定子故障。 通过比较每个相位的绕组电阻，可以看到高电阻连接。 接地故障可通过对地绝缘测试发现。 通过相互比较阻抗和电感读数，可以观察到污染情况，污染范围包括冷却液、油和水以及过载绕组。 伺服电机上的污染会在故障发生前几个月开始显现其不良影响。 总的趋势是，会出现显示面板上有过流情况的维修电话。 在通过艾里逊坐标测量机系统对工单进行回溯和跟踪后发现，过电流故障很可能会更频繁地出现，从而需要下达更换伺服电机的工单。 地区规划人员已收到通知，提醒他们注意过流情况，以及如何在伺服电机完全失灵之前检测到过流情况。 与被动行动相比，有计划的维护可以避免成本。 与完全倒卷相比，电机车间的清洁浸泡和烘烤更便宜、更有效。

适用的成本规避电子表格按以下方式在 QNPM 网络中依次共享：

已发出 MCA 工单

电工对电机现场的回应

对多重标准分析测试进行分析并做出判断

Implement the action plan. For example, if the servo motor has been tested well using MCA, a root cause investigation will be initiated to check for other possible causes of failure, such as burnt-out fuses, SCRs, drivers, cables, or motor connectors. If cable replacement is required, the costs of active and passive repairs will be compared against the maintenance history (Table 1).

Allison Transmission Company prefers proactive maintenance to reactive maintenance, especially from a financial perspective. For example, in 2002, Allison saved a total of $307,664 by implementing management and oversight programs (Figure 6).

Single-phase test

When testing three-phase motors, the ALL-TEST Pro™ MCA device performs well for comparing windings. But what about single-phase testing? What, is single-phase electricity no longer used in industrial applications? Allison uses DC motors in many applications, which have one set of field windings (two wires) as well as inner poles and armature (two wires). The engineering test department uses eddy current dynamometers to simulate load tests on all manufactured transmissions, which also have two sets of windings but only two wires. How are these two types of devices compared? First, the windings are subjected to MCA testing, and then the information is stored in a database along with the nameplate information to identify similar motors. Finally, similar windings are compared, and problematic windings are exposed (Table 2).

 

Case Studies

Figure 7: Testing the machining center using MCA

 

Case Study 1: Infrared Thermal Imaging Technology (IR)

An electrician discovered an overheating motor while forecasting an infrared circuit. The motor was a 7.5-horsepower coolant pump, and there were five identical machines in the group. A work order was submitted for motor circuit analysis, which was subsequently completed and indicated that the motor was not faulty. A vibration analysis work order was issued, revealing that a bearing failure was causing the temperature rise. The coolant pump was replaced, and the temperature returned to normal for the other machines in the group. This particular machine tool is a machining center for gearbox housings. Historically, coolant pump motor failures have caused production losses and could even lead to assembly line downtime.

Case Study 2: MCA and DMM and Insulation-to-Ground Testing

An electrician, while predicting infrared circuitry, noticed a 5-horsepower motor overheating on a machine with four drill bits, which was drilling. Comparing impedance and inductance readings revealed contamination in the motor windings. Impedance and inductance could not be detected using a DMM or insulation-to-ground tester. Resistance and insulation-to-ground tests were normal. Since this model of motor was not in stock, it was sent for repair. MCA analysis was performed to determine the cause of the contamination. The motor shop performed a complete dissection of the motor, and after knocking off the bell at the end, it became clear that the problem lay with a liquid in the windings. The unknown liquid was poured into a sample bottle. The auto repair shop performed extensive repairs on the windings, and after determining the liquid was a mixture of coolant and hydraulic oil, they also performed an epoxy sealant on the area. The motor was returned and installed in less than 24 hours. The machine drilled a series of holes in the bracket for mounting the transmission. If the machine were to completely malfunction, the assembly line would be shut down. The estimated lead time for ordering a new motor was three days.

Case Study 3 #8 Air Compressor, 4160 Volts, 1000 Horsepower

On June 18, 2003, power room workers provided data to the reliability department requesting a review and clarification of the ALL-TEST IV PRO™ 2000 readings for the 4160-volt, 1,000-hp motor on air compressor #8. An 84.5% resistance imbalance was found. The motor was tested first at the motor control center (MCC) and then at the motor connector. A faulty connection on the terminal block was found and corrected, reducing the imbalance to 0.17%. This case further demonstrated the practicality of the MCA, as the 4160-volt connector on the compressor did not need to be disassembled and reassembled. The motor did not need to be disassembled and sent to the motor shop supplier, McBloom Electric. This saved unnecessary motor repair costs and some compressed air losses from production equipment.

Summarize

Motor circuit analysis has had an impact on Allison. With the approaching NFPA 70E PPE issue, offline motor circuit analysis is invaluable and safe. Our perception of the motor world may have changed from the past when multimeters and ground insulation testers were sufficient. Allison Gearbox believes in and relies on systems that enable continuous and accurate proactive maintenance.

 

About the author

Dave Humphrey is a senior electrician who has worked at General Motors for 18 years. His father was an electrical contractor, and Dave began working with him at the age of 10. Before joining GM, he worked for several contractors. Dave is certified in motor circuit analysis, infrared thermal imaging, and vibration analysis. He has taken numerous courses in motor diagnostics, ultrasound, and root cause analysis. Dave is a Purdue University graduate and a Certified Electrical Master. Dave taught motors, transformers, troubleshooting techniques, and national electrical codes in the GM Apprenticeship Program. Currently, Dave teaches motor circuit analysis at Allison University. Dave is the vice president of the Human Home Organization in his county, providing wiring for all homes in the program. Dave is a very active homemaker and a Christian.