Motors and electrical machinery system operational costs
Total operational cost of motor and electrical machinery unit consists of three main factors directly linked to the cost. These are: cost of purchase, cost of electricity consumed by the motor during its operation, and expenditures on maintenance and service activities for the motor. The dominant component here is, without a doubt, the cost of electricity and service which may represent over 95% of total operational cost of the motor throughout its life cycle. The fact that the electricity consumption component, directly depending on the parameter which is the motor efficiency, represents the vast majority of total operational cost, should set a clear path on how to select a motor, how to use it, and how to maintain it in excellent condition in specific machinery. Therefore, only the user, who selects, operates and services the motor and machinery, can decide on fulfilling only the minimum legal requirements or, taking a step forward, optimizing selection and operation of a drive unit.
Where is the profit?
A comparative economic computation for motors with different efficiencies, as well as a cost analysis of energy and operation for damaged motors are not complicated and allow real determination of profits from selection of correct motor and costs of its operation and maintenance in good condition. A motor efficiency level analysis itself does not give a full picture because it does not make it clear how single efficiency percentages (deteriorated by internal and non-diagnosed damages of the motor and machinery, such as damages of bearings, stator, rotor, machinery misalignment, damages of couplings, etc.) translate into losses or savings of electricity consumed by the motor, of which service life is computed in the tens of thousands of man hours. Lack of this knowledge causes that the efficiency parameter is frequently not considered with due regard at the stage of selection and the way of operation of the motor, which results in selecting solutions that are not cost optimized. The motor user is frequently not aware of the importance of electric repairs (rewinding of damaged motor) to the motor parameters. Every single replacement of windings results in reducing efficiency and if not carried out with due care, this loss may reach even 3 to 10% or more. In addition, motor repairs may result in changes not only to the losses but also to motor parameters (losses, output power, cosϕ). This is where the Elmodis measuring system comes in, computing specific diagnostic indicators and their values, as well as reasons for efficiency decrease and deterioration of operating parameters of the motor.
Maintenance cost
Higher efficiency does not only translate into smaller electricity bills. As already mentioned, losses in the electric motor are mainly transmitted in the form of thermal energy. The higher the efficiency of the electric motor, the lower the loss level; thus, less energy drawn from the grid is converted into thermal energy. This results in lower operating temperature of the motor, which may be of key importance to its operation. Two main causes of motor failures, failures of bearings and damages of winding insulation, are rooted in the excessive operating temperature. Motors with higher efficiency, due to smaller energy losses in the form of thermal energy, prevail in this field over motors with lower efficiency: lower operating temperature of the motor means better operating conditions of bearings and winding insulation, therefore their longer service life. Optimization of operating conditions enables reduction in frequency of periodic inspections, or scheduled downtimes, therefore service and maintenance costs, while increasing the drive unit availability. These costs are probably more difficult to be calculated directly, already at the motor selection stage; however, this fact should be also taken into consideration by using a correct machinery supervision and diagnostic system (Elmodis). Moreover, the motor operational costs should also include the indirect costs – the losses resulting from downtimes of a piece of equipment or production line in case of the motor failure. While the first three direct costs are possible to be calculated or estimated, both by the motor user and its supplier, the component linked to the downtime costs can be estimated only by the user. Line downtime costs may be many times higher than the motor cost, which caused this downtime. In key applications, using highly efficient motors seems to be the only reasonable option, not only due to the fact of reduction of the direct costs but also by minimizing the risk of generation of the indirect costs caused by failure.
ELMODIS edge hardware (with EADEC – Elmodis Advanced Edge Computing) is an advanced module for monitoring, diagnostics, and prediction of damages with built-in specific algorithms for various types of electric motors and electric motor-powered machines. The module uses only the measurements of supply voltages and currents for the monitored motor in order to determine parameters specific for a given motor, describing its operation.
The system developed by Elmodis is based on dedicated measuring and processing modules of ADEC type (Elmodis Advanced Distributed Edge Computing), using patented (Patent Pending) and advanced signal processing and analyses for each motor/machinery and using a unique technology of computations distributed between the ADEC modules (e.g., within a specific process line, within a factory, etc.).
Significant qualitative and quantitative indicators (KPI – Key Performance Indicators) computed in this way are transmitted to the server-based cloud application. From there, they are made available via a web browser as a page dedicated to the application. Moreover, additional statistical, reliability, and predictive analyses linked to the condition, energy consumption and quality are carried out in the cloud application. [to be continued…]
Źródło: Artur Hanc
