When AWE Newtech Limited (Newark, UK), a leading manufacturer of electric motor winding impregnation machines, realized that significant cost savings for their flagship machines could be achieved by introducing distributed control, they turned to our partner, Machinery Control Systems (Telford, UK) to develop a suitable process control scheme. In the picture on the left: a multi-station machine for soaking stator windings. This is one of the largest machines, its length is 12.5 m. Newtech machines are used to impregnate the windings of stators up to IEC 200 / NEMA 320 (weighing up to 100 kg) with insulating resin. The machines use resins, which must be processed at elevated temperatures to achieve their required working properties. Before impregnation, the stators are heated to reduce the viscosity of the resin, which helps its penetration. Then they are heated after impregnation so that the resin hardens. Heating is provided by electric lamps emitting intense infrared radiation in the short-wave range (SWIR). Due to the high throughput, an increase in the stator temperature from one process level to the next is provided by many successive heating stations. Usually, machines contain from 20 to 60 heating stations. On the left there’s a typical stator
Each heating station includes an infrared lamp module. There are two versions of the module, 6kW and 8kW, depending on size of the largest stator, with twelve or sixteen quartz halogen lamps with a power of 0.5kW. Each lamp is controlled independently so it only turns on if the stator is present directly below it and the stator temperature is lower than necessary. The lamps turn off during indexing in order to save energy. In early machines, each lamp was controlled by a separate PLC output, which required a large number of I / O modules and a huge amount of wiring between the control cabinet and the lamps. Their elimination led to a significant reduction in cost. In the figure on the left: a lamp module with a total power of 6 kW with twelve infrared lamps of 0.5 kW each
A large machine can contain up to 1000 lamps with a power of 0.5 kW, each controlled by a digital output to a PLC (programmable logic controller, PLC), plus 5-6 kilometers of wiring between the cabinet and the lamps.
The cost of the PLC I / O modules including the wiring work was a significant part of the total cost. Tightly packaged wiring was also dangerous, as the machine could be seriously damaged if ignited. The Flexis process control board, which is installed in each lamp module, eliminates I / O and a significant portion of the wiring. In close collaboration with Newtech engineers, a detailed functional specification, and after – design specification for hardware and software were developed. According to these specifications, Flexis engineers designed and manufactured a prototype board. The main function of the board is to control the lamps to achieve optimal heating in the stators with the most efficient use of energy. The side of the board that controls the power supply carries real current and voltage values for each lamp consuming about 2A at ~ 230V. The case is equipped with a fan to cool the boards; despite this, the circuit operates at 50-60 ° C. In this regard, were used components of increased reliability, which are designed for continuous operation at high temperature. The boards are connected via a network to the PLC that controls the entire machine. Since end-users usually indicate the PLC model used in their machines, many of which will use their own network, we’ve implemented the ability to connect to the most widely used networks – ProfiBus for Siemens PLCs, DeviceNet for Allen-Bradley PLCs, CANOpen and MODBus, as well as Ethernet and RS485, for communication with PC-based controllers. We also helped Newtech to develop software and implement it to the network on the PLC. The board was designed for transparent operation with respect to the PLC so that the original PLC code could control the lamps without significant changes. Due to the available computing capacity of the boards, we’ve made much greater functionality, including the ability to smoothly start, which increases the lamp lifetime, plus control of the lamp life, and error messages such as fan or lamp failure. The second stage of development for the further reduction of the cost included the removal of the interface for the infrared pyrometer used for non-contact measurement of the stator temperature, processing the output signal of the pyrometer in the processor.
In the figure on the left: the process control board for the 6 kW module shown above Having tested the prototype, Flexis organizes the manufacture of boards in batches of 100 pieces. Newtech benefits from significantly reduced labor and material costs, easier assembly and improved performance.