An important electrical parameter in machine tool equipment is the effective power of the motor. This parameter can be precisely monitored with Phoenix Contact's Contactron motor manager, which can detect high overload and low load conditions immediately. Because the motor manager can issue alarms and maintenance tips in time before the motor fails to stop, it can effectively protect the machine tool equipment, so that the availability of the machine tool equipment is significantly improved.

In industrial applications, electric motors are generally used to start production. Under normal circumstances, it is protected by the motor current protector which plays a protective role according to the length of overcurrent time; Or it is protected by a motor protection switch that provides overload protection according to the load size. However, when the motor's cooling fan is reversed, or the cooler is blocked and cannot achieve normal cooling, what happens to the motor?

FDT/DTM software for parameter assignment, fault diagnosis and production data acquisition

Current monitoring is often inadequate

There is no doubt that when the temperature of the motor rises to a certain critical value, it will lead to the failure of the motor. As a solution, a thermistor can be installed in the winding of the motor, and this thermistor can be connected to a control switch that can cut off the motor current if the motor temperature is too high. The thermistor and temperature control switch together constitute the comprehensive protection of the motor. However, this protection scheme has little protection for its subsequent mechanical equipment or mechanical structures, which cannot avoid the failure of the worst working conditions.

The main reason for motor failure is that many users reserve too few varieties of motor variants in order to reduce inventory. In practice, about 90% of the working load of the motor only reaches 40% to 60% of the rated power, which is not within the range of its best working characteristics. The overcurrent protection device of these motors is set according to the rated power on the motor nameplate, and is set according to the parameters of the motor within the range of the best working characteristics. When the load changes, even small changes, will be reflected in the power factor and efficiency; The change in motor current remains almost constant. However, the mechanism can still be overloaded, and the problem does not show up in the pure current monitoring system. This will have serious consequences for the machine tool equipment: the mechanical device driven by the motor is seriously damaged and expensive.

Detect effective power to improve protection of machine tools

According to this monitoring method, alarm information can be quickly sent, or the power supply of the machine tool equipment can be cut off. The detected data, which can draw the running curve of the motor, truly reflect the working condition of the machine tool equipment; Clearly show the difference between the theoretical observation data or the theoretical calculation data. With this Contactron motor manager, the effective power of all machine tool equipment components and instruments installed behind the motor, such as bearings, mechanical components, etc., can be taken into account and displayed together and can be quickly safeguarded (Figure 2). Compared with pure current protection, monitoring based on effective power can also play a role in safety protection at low loads, such as the loss of oil operation of the pump, etc., to complete tasks that have long been required to assist the use of effective power monitors.

The saved start-up operation curve is an important part of the equipment's operating status, because it can be used as a reference for equipment aging, dirt level or wear condition. Using this curve, we can accurately determine all the monitoring parameters, the upper and lower limit values of the monitoring, and the alarm, prompt or cut-off power supply, parameter assignment and other information corresponding to these limits. The parameter assignment of the manager is carried out using DTM (Device Type Manager) software, which makes the motor manager compatible with FDT (Field Device Tool), such as Phoenix Contact's automation management software AutomationXplorer. In this way, the motor manager can be integrated uniformly and stably into a variety of engineering tools or control systems.

Only the effective power allows the entire range of upper and lower limit loads of the machine tool equipment to be monitored. As the protection switch of machine tool equipment, it ensures that the machine tool equipment has a high availability, and thus also guarantees a high production capacity. Using its effective power monitoring function, it can detect faults and interference during use in time, thus avoiding equipment shutdown failures. As the basis for the calculation of technical data, it is based on electrical data: the electrical data obtained by using the motor as a sensor. Time-consuming additional sensors and even expensive sensors, such as pressure sensors, flow sensors or differential pressure sensors, can be omitted. Other electrical parameters, such as the operating time of different gears, the total operating time of machine equipment and the energy used, can be captured while optimizing maintenance.

Easy and convenient reassembly with motor supply cable

With the motor manager with integrated current converter, the 16A current motor can be directly monitored and installed without taking up too much space. When the current of the motor is larger, a special module can be used, combined with an external current converter, to monitor the motor at all power levels. Therefore, the use of this instrument to monitor the motor and machine equipment becomes very simple: the use of only the power cable to the motor. In this way, it is also possible to supplement the existing equipment with this motor manager, and in the future, it will be able to provide users with accurate machine tool equipment operation data.

The switching off of the three-phase electrical load is done by specialized mechanical relays or by Contactron series non-wear semiconductor relays that use the digital output of the motor manager module for power supply and power off control. At this point, the motor manager provides the safety monitoring and protection of the pump, console or cutting machine, and evaluates the electrical energy required for each device. In this monitoring process, no matter whether the motor manager is powered autonomously or using fieldbus power supply, it can complete this task well.