Motor Energy Controller (energy saving device)

Brand Name

Motor Energy Controller(MEC)

Motor Energy Controller for induction motors

• Reduces Electric power consumption 10~30%
  
• Improves Power Factor 10~20%
  
• Extends Motor Life
  
• Improves Product Quality
  

Size & Weight

1. Motor Energy Controller

The inefficiency of an AC induction motors worsens when the workload of a motor is less than full. When the actual work load of the motor is lower than the rated load, the sensing circuit reduce the energy being fed to the motor to the exact level the motor needs. This has the effect of reducing motor consumption.

Motor Energy Controller (MEC) controls the AC induction motor so it always functions at its optimum efficiency. MEC reduces excessive energy waste in three-phase AC induction motors. The controller is a solid state(SCR) unit providing a reduced voltage start, reduced energy consumption and improved power factor.

The unit monitors the phase lag of the current and voltage relationship in a motor that is operating at less than full mechanical load. The M.E.C controller cuts back the voltage to precisely what the motor requires to maintain the rated speed and torque under the present load.

2. Specifications

AC Voltage	220, 380, 440 Volts
Hertz	50 / 60Hz
Horsepower	3 - 220hp
Load Type	Three-Phase AC Induction Motors
Output Stage	Six SCR's Full Wave In-line
Environmental Considerations	Ambient Temperature Operating Range : -10 to 40°C 85% Non-condensing Humidity
SCR Peak Inverse Voltage	Line Voltage: Repetitive Peak Off-state and Repetitive Peak Reverse Voltage 220V         800V 380-440V       1600V
SCR Amperage Rating	Continuous Rating Motor FLA
RC Snubber	Snubber networks in each phase prevent false firing due to dv/dt
Wiring	Straight through configuration no control wiring
Mounting	Units may be wall mounted one inch apart wit heat-sink fins vertical

3. Background of the M.E.C

M.E.C. was originally proposed and developed by Frank Nora (NASA) in the mid to late 1970's as means of reducing energy waste on AC Induction motors. The technology was designed to monitor the power factor of the motor, and to reduce the voltage an current when the power factor is dropping. The correlation between the power factor and the motor's efficiency is such that when the power factor begins to fall, the efficiency of the motor falls as well 

PATENT(NASA) : P.F.C	P.F.C : VECTROL INC. Model : V.E.S(Vectrol Energy Saver) Application : Woodward &Lothrop Dep. Store Escalator : Saving rate : 30 ~ 40%	P.F.C : Commander control Inc.(Left) Model : Power commander M.E.C : Motor Energy Controller(Right

4. Principle of Energy savings

• Causes of energy waste:
  - MOTOR OPERATION BELOW DESIGNED LEVEL
  - ACTUAL INPUT VOLTAGE HIGHER THAN RATED VOLTAGE
  - DESIGN INEFFICIENCY IN MOTORS(HIGH SLIP)
  
• Electric motors are estimated to consume over half of all electricity and over 70% of all electricity in industrial applications
  
• Most AC induction motors waste energy. An AC induction motor can consume more energy than it actually needs to perform its work, particularly when operated at less than full-load conditions. This excess energy is given off by the motor in form of heat
  
• Studies conducted by the Electric Power Research Institute(EPRI) reveal that over 60% of industrial motors are operating under 60% of their rated load capacity.
  
• Idling, cyclic, lightly loaded or oversized motors consume more power than waste energy, when they are not working
  -> Generating excessive utility costs an unnecessary motor wear.
  

■ EFFECT OF VOLTAGE CONTROL ( AC Induction Motor) Although the devices sense power as a control variable, what they actually control is voltage, to provide just the amount needed to maintain rated speed and torque for a particular load. The effect is what's important : -> Reducing the voltage applied to motors operating at less than full load reduces their losses(see Figure 1). ■ ENERGY SAVINGS : M.E.C(Motor Energy Controller) The Motor Energy Controller senses the drop in mechanical loading(efficiency) and adjusts the energy to the motor to the precise level required to perform the mechanical work - Wasted energy that previously was dissipate in the form of motor losses now is conserved The Motor Energy Controller automatically and electronically down-sizes the motor to match its work load. It adjusts power consumption proportional to motor loading conditions without altering motor RPM - Reduces Energy Consumption (kWh), and Demand(kW) - Improves Power Factor - Energy Savings

5. Losses of an AC Induction Motor

■ Motor Losses

• AC Induction Motors offer higher efficiency ratings for motors at or near full load and the lowest efficiency at no load or lightly loaded.
  
• Efficiency is the ability of the motor to convert electrical energy into mechanical energy.
  
• Efficiency losses occur at all points of motor load but are most significant from 60% to no loads.
  
• Motor losses fall into five basic categories.

6. Motor Energy Controller Technology

■ Operation of the M.E.C

• Energy saving is achieved by means of a closed loop feedback system
  
• The sensing circuits in the M.E.C compare the voltage and current waveforms at the motor
  - because this is an induction circuit, the voltage and current and current waveforms start at different times
  
• The smaller the load on the motor, the greater the lag in the current waveform. At no load, the motor is least efficient and the waveforms have the largest distance(phase angle) between them
  
• We measure the distance between the two and compare this difference to an operational distance. The difference between the actual waveforms and the ideal is compared and gives us a sum that we call the error voltage.
  
• This error voltage is used to create a firing pulse that determines the length of time we send power to the motor.
  
• The larger the error voltage, the shorter the firing pulse. The smaller the error voltage, the longer the 'on' time of the firing pulse of the SCR's

In this manner we can regulate the amount of energy that the motor receives to perform it's work. The speed of the circuit is such that it can change the signal to the motor one hundred twenty times per second(120Hz). This speed is much faster than the motor can operate, and is necessary to keep the motor from stalling under any all motor functions.

■ Control Implementation

Structure of the M.E.C

Voltage waveforms

Principles of Energy savings

7. Typical Energy Saving Rate(M.E.C)

• Although M.E.C devices can save some energy at any load level, they save the most at low loads.
  
• For a given application, determine the load profile and estimate the power savings using Fig. 8 or Fig. 9
  
• A single-phase motor that spends 20% of its operating time at full load and 80% at one-quarter load will reduce energy use by about 25%
  

8. Effective application of the M.E.C

■ Introduction to the Motor Survey

• The Motor Energy Controller is most likely cost effective in situations where motors operate at constant speed but spend a lot of time at low loads
  
• Energy cannot be reduced on a motor that is performing work at its rated load
  - Gains in motor energy conservation can occur at unloaded intervals(or during the unloading cycle) of the driven machine.
  - Energy conservation is the removal of waste energy while still performing necessary work.
  
• Your primary goal in the survey is to identify motors that are cyclical (load and unload), oversized, over-voltage , and constant speed.
  
• It is important to look for constant speed, variable load, a large watt pool(big motor), and a low power factor(0.40 or less)
  
• Consider the work being performed by the motor applications
  - Is the motor unloaded for a longer period of time than its loaded cycle(i.e low PF)?
  - Is the motor's horsepower greater than necessary?
  - Does the motor have a constant speed application?
  - Does the motor use a special starting or wiring system?

■ Motor Energy Controller Applications