Optimized Motor Performance in Quarry & Mining Conveyor Belts

MOTOR EFFICIENCY CONTROLLER IN
QUARRY FIELD TEST

OVERVIEW
This case study presents measurements and explains the results of a field test conducted with the advanced SinuMEC (Sinusoidal Motor Efficiency Controller) developed by PowerSines. The SinuMEC 20HP/15KW model was installed at the Vered Quarry in Israel to control an inductive electric motor of 20HP (15 KW/30A) which operates a conveyer.

BACKGROUND - ELECTRICAL MOTORS
In many industrial applications, electric motors are designed to develop the maximum torque during the startup sequence (for example: to start a fully loaded conveyer, mixer or other equipment). However, after the startup sequence is completed, and the requirement to the torque and power decreases, the motor usually works at partial load. It is very common that under these conditions the motor is loaded at only 30%- 60% of its nominal power. In this mode, motor efficiency decreases (low Cos F and relatively high working current), creating an energy efficiency problem for manufacturers, plants and production sites such as the Vered Quarry.

THE SINUMEC
The SinuMEC system improves the parameters of electric induction motors operating in partial load mode. This substantial improvement is achieved through providing reduced SINUSOIDAL voltage when the motor is running at partial capacity. Controlled by a powerful microprocessor, the SinuMEC continuously measures the motor load and automatically switches from SAVING mode to BYPASS mode when the motor load increases above the certain threshold. This enables enhanced energy savings and efficiency improvement without compromising operational performance.

The SinuMEC has been designed and developed using a proprietary technological platform for controlling line voltage. The SinuMEC provides pure SINUSOIDAL voltage waveform when the motor starts and while it runs. Unlike other solutions based on phase-control methods, the SinuMEC does not generate harmonic distortions or electromagnetic interference, which are harmful for the motor. Moreover, it does affect motor torque and limits motor wear which results in further prevention of energy losses.

Moreover, the SinuMEC offers more than energy savings; it is an all-in-one solution for improving efficiency and controlling electric motors. The SinuMEC system integrates Reduced Voltage Start (RVS™) mechanism that enables starting electric motor at the maximum torque and at a reduced current (typically 1.5 -2.5 times the nominal).

TEST METHODOLOGY
In order to measure motor performance with and without the SinuMEC system, the SinuMEC installed at the Vered Quarry was programmed to switch automatically between SAVE and BYPASS modes every one minute. The measurements of Voltage, Current, CosF, VA and Power were recorded into the power meter with two-seconds resolution. After one hour of data recording the log files were uploaded onto a computer for analysis and results calculations.

The results of this test are presented in the table below:

The motor was loaded at about 30%.

In addition, the startup current was measured when motor starts with and without SinuMEC. With the SinuMEC the motor started smoothly with the start up current being only 1.6 times the nominal current while developing the maximum torque needed. Without the SinuMEC, the startup current can reach levels of 6-8 times the nominal current.

CONCLUSIONS
While a moderate reduction of Power (18%) was observed during this test, all other parameters (A, CosF, VA and VAR) were significantly improved. This also results in additional indirect savings which offer added benefits to the direct energy savings.

1) Direct Savings
Assuming 6000 annual operating hours, the direct energy savings will be 5,340KWh. Saving = (5,045W - 4,155W) x 6000H

2) Conduction Losses
Estimated conductivity losses in industrial sites are about 7%. Power losses are proportional to the square of current (Ploss = RI2 ). Therefore, reducing current by 48% results in reduction of power losses by 73%. This means additional saving of over 5% in electricity.

3) Maintenance Cost Reduction
Using SinuMEC reduces thermal stress and iron losses while optimizing motor performance, therefore reducing motor Life Cycle Cost (LCC) and extending its life span.