The third generation of Large Motor Controls brings mine-proven solid-state performance and reliability to equipment powered by large DC motors.
LMC controls use microprocessor-driven IGBT devices for the control of traction motors and other systems in scoops, haulers, shuttle cars, locomotives, personnel carriers and utility vehicles. They are built for equipment drawing power from trolley lines, batteries, trolley/battery combinations, reeled cable and AC/DC supplies.
LMC controls power DC motors running on supplies from 72 through 600 volts DC. They produce up to 1300 amps in motors, without a bypass, and generate maximum motor torque at all speeds.
Cableform's proprietary microprocessor control of IGBTs (Isolated-Gate Bi-polar Transistors) provides LMC-powered mining equipment with these performance advantages:
- Maximum motor torque at all speeds
- Smooth controlled acceleration
- Smooth controlled braking
- Reduced electric power consumption
- Cooler running motors
- Solid-State diagnostics
- Motor protection circuits
- Reduced mechanical stress
- Reduced maintenance
DC Power: The IGBT Power Device
IGBTs are solid-state switches turned on by a very low-powered signal voltage, then turned off by removing that voltage. The LMC's microprocessor-controlled ON/OFF operation runs IGBTs at high frequencies from 2kHz up to 10kHz. Motors receive from 2,000 to 10,000 pulses of DC current per second from LMC controls. High-frequency operation has three important results; no motor-compatibility problems, high torque at all speeds, high current multiplication at low motor rpm.
LMC Technology results in simple power circuits. This technology increases reliability and replaces the following SCR motor-control components with a single IGBT: main SCR, commutation SCR, commutation firing circuit, commutation capacitors, and choke. LMC controls eliminate the miscommutation, bypass and contactor problems found in SCR controls. They also eliminate all the contactor problems associated with magnetic controls.
Total Machine Control
Total Machine Control is available through the LMC's microprocessor. Control of a vehicle's pump motors, parking brakes, sanders, compressors, conveyors, lights and other devices is an optional feature. Total Machine Control is available for single and tandem-vehicle operation.
LMC controls are built for use in an extensive range of new and old equipment. They are the maintenance and performance standard for installation in all DC powered vehicles.
Short, two-microsecond on-pulses dramatically reduce current surges to the armature during braking. This decreases wear on the motor commutator and produces a smooth braking action.
Reduced Motor Heating
A total pulse duration of 100 microseconds creates almost identical peak and average motor currents. This significantly reduces I²R losses, resulting in cooler motors that are more efficient and reliable.
Low-inductance motors behave like high-inductance motors under the LMC's high-switching frequencies. This eliminates the motor compatibility problems associated with SCR controls.
Protection circuits detect and respond to any motor or control fault condition in an instantaneous 7 microseconds.
Easily Interfaced Operator Controls
LMC controls contain solid-state contactor drivers which optically isolate operator control switches from high-voltage circuits. This allows the use of durable, low-voltage switches.
LMC technology results in greatly simplified circuits which provide safe, reliable operation. Trouble-shooting is simple. There is no miscommutation, and LMC controls are energy efficient.
LMC controls provide superior reliability because no commutation is required and all semi-conductors are 1200 volt devices filtered from the trolley line by a surge-suppressor-protected capacitor bank. LMC controls eliminate the problems cause by:
- Ddiscontinuity of the power supply as the pantograph bounces
- Substantial negative ring of the supply voltages
- Positive-going transients caused by switching-off other machines
The LMC's input-capacitor filter forms a series circuit is with the natural inductance of the reeled-cable power supply. This produces a constant current source to the LMC control while limiting voltage transients from the power center. LMC controls provide significant advantages for reeled-cable powered equipment.
Battery and Trolley/Battery
LMC controls provide superior battery and motor performance and eliminate all the problems associated with SCR controls and contactors. The high-frequency operation and short, microsecond pulse duration of LMC controls provides braking control and motor compatibility advantages. The smooth, almost continuous, battery current results in cooler motors that are more efficient and reliable. The use of battery power is extremely efficient. The power source for LMC controls can be battery, trolley or both.
DC Pump Motors
The LMC series of controls includes single-direction pump controls.
AC Power Supplies for DC Motors
LMC controls are fitted with an input rectifier for AC supplies up to 480 volts, 3 phase. Standard LMC specifications for DC voltages apply.
Engineered For Performance and Safety
- Solid-State reliability
- Programmable operating features
- Computer diagnostics and operational display
- Motor and control protection
- Optimum performance
The microprocessor's digital logic constantly monitors and controls all functions voltages, and currents. Commands are sent to the logic by the vehicle operator controls. The logic executes the commands and maintains the desired levels of performance while sampling information for any abnormal conditions.
The data terminal is used to customize equipment performance. The terminal's display menus provide rapid access to operating status, features and diagnostics. The menus quickly lead through the reading and setting of all operating parameters. For example, drive and break settings can be individually adjusted to produce the optimum levels of torque, acceleration, and braking.
Fault-detection and safety circuits record any faults that may occur and protect the motor from dangerous operating conditions. The data terminal can display the motor control's status which provides for the fast diagnosis and repair of almost any problem. Operator controls for functions like forward/reverse, speed demand, and others can also be tested with the data terminal.
LMC controls bring advanced IGBT power technology to the operation of DC traction motors. The LMC microprocessor provides reliable, energy-efficient performance while significantly reducing operating costs. The data terminal makes maintenance of the entire system a simple task. The technology built into LMC controls makes their performance outstanding.
- Rradio remote-control interface for single and tandem-vehicle operation
- Total tandem vehicle control via a RS485 connection-including lights, compressors, sanders, brakes, speed
- Wheel-Spin control
- Anti-Stall control-stationary motor high-current protection
- Anti-Lock braking
- Low-Voltage alarm and optional power cutoff
- Low air-supply alarm
- Motor-Current differential alarm
- Closed-Loop speed control
- Battery charge-status display
- Operator display
LMC controls generate more torque at low speed demand than all other types of controls. Magnetic controls limit motor speed by reducing the motor voltage (speed) and current (torque) resulting in a substantial loss of torque in the medium-to-low speed range. SCR controls limit voltage and current, but generate a moderate amount of start-up torque with a 3:1 current-multiplication factor.
LMC controls boost torque and reduce electric power consumption when controlling medium-to-low speeds by supplying the motor with high current at low voltages. This is accomplished by the LMC's short IGBT pulses (2 to 100 microseconds each) plus the application of flywheel diode currents to maintain an almost constant motor current during the off portion of each pulse cycle. This produces a superior ratio of motor current to supply current (current multiplication).
Trolley-Line and Reeled-Cable Powered Equipment
7:1 Current Multiplication
LMC controls generate up to 7 amps in the motor for every 1 amp drawn from the power source. This is a significant 7:1 current-multiplication factor which produces 100% of a motor's torque capability across the entire speed range. Advantages for line-powered equipment are:
- Reduced demands on power centers
- Eliminates voltage transients caused by magnetic controls
10:1 Current Multiplication
LMC controls generate up to 10 amps in the motor for every 1 amp drawn from the battery. This is a significant 10:1 current-multiplication factor which produces 100% of a motor's torque capability across the entire speed range. Advantages for battery-powered equipment are:
- More working time per battery charge
- Cooler batteries
- Longer battery life
The current-multiplication factor will vary according to the motor, peak-current limit, and load. Current multiplication is usually the greatest when vehicles are at a maximum effort. This is the condition which overheats motors, drains batteries and causes power center brownouts. LMC technology eliminates the problems caused by maximum tractive effort while providing more working power.
LMC controls consume less power than all other types of controls. For example, 300 amp peak currents are pulsed by SCR controls to maintain an average motor current of 200 amps. The LMC's high-frequency operation pulses 210 amp peaks to maintain an average motor current of 200 amps-a significant energy savings. Higher average currents produce even greater savings. The LMC's efficient use of energy results in reduced power consumption for trolley-line, reeled-cable and battery-powered equipment.