Electrical Drive: What is it? (Block Diagram Included)

What is an Electrical Drive?

An electric motor connected directly to a supply operates according to its machine design, load and supply conditions. An electronic drive can regulate the applied voltage, current and frequency to control the motor’s motion.

An electrical drive is the system that converts supplied electrical energy into controlled mechanical motion. Depending on the application, it can regulate speed, torque, position or direction.

The drive can match motor output to the process instead of running the motor at one fixed operating point. This can improve process control and, for variable-torque loads such as pumps and fans, reduce energy use when full speed is unnecessary.

Electrical drives include more than the controller alone. A typical system contains the power supply interface, power converter, control unit, one or more electric motors, sensors where feedback is required, mechanical transmission and driven load.

Software implements control logic, limits, sequencing and communications. Accuracy still depends on the control method, motor model, sensors, commissioning and mechanical system. A drive must be selected and tuned for the required torque-speed range and dynamic response.

Drive systems are used in industrial production, transport, lifts, textile machinery, conveyors, robots, pumps, fans, compressors and household appliances. Some need variable speed, while others use a drive for soft starting, torque control, positioning or regenerative braking.

The electric machine is the prime mover in an electrical drive. Diesel engines, turbines and hydraulic motors are different prime-mover technologies, although hybrid systems can couple them with generators and electric motors. The term drive can also refer narrowly to the electronic converter, so equipment documentation should define its scope.

An early electrical drive application was Moritz Hermann von Jacobi’s 1838 electric boat demonstration on the River Neva. Its electromagnetic DC electric motor drove paddle wheels and drew power from a chemical battery. Calling it the first complete drive applies modern terminology retrospectively; practical industrial electrical drives developed through many later advances in motors, power supplies and control.

The block diagram above shows the basic energy path from source and controller through the electric motor to the mechanical load. The load is the driven equipment, such as a fan, pump, conveyor or washing-machine drum. In a closed-loop drive, sensors return speed, position, torque or process feedback to the controller.