Basic Components of Electric Drive System:
The electric drive system has five main functional blocks namely a power source, Power Modulator(Converter), a motor, a mechanical load and a Controller(which incorporates sensing unit and control unit).Why It is Needed? A drive operates and controls the speed, torque and direction of moving objects. Drives are generally employed for speed or motion control applications such as machine tools, transportation, robots, fans, etc. The drives used for controlling electric motors are known as electrical drives.
An electrical drive is defined as a form of machine equipment designed to convert electrical energy into mechanical energy and provide electrical control of the processes. The system employed for motion control is called an electrical drive. 2.2 ELECTRICAL DRIVES AND THEIR BLOCK DIAGRAM.
Frequent starting, braking and reversing. The disadvantage of D.C. drives is the presence of a mechanical commutator which limits the maximum power rating and the speed. The variable speed applications are dominated by D.C. drives because of lower cost, reliability ad simple control.
Now according to the design, the drives can be classified into three types such as single-motor drive, group motor drive and multi motor drive. The single motor types are the very basic type of drive which are mainly used in simple metal working, house hold appliances etc.
A Variable Frequency Drive (VFD) is a type of motor controller that drives an electric motor by varying the frequency and voltage supplied to the electric motor. Other names for a VFD are variable speed drive, adjustable speed drive, adjustable frequency drive, AC drive, microdrive, and inverter.
Load Equalisation in Electrical Drives. Definition: Load equalisation is the process of smoothing the fluctuating load. The fluctuate load draws heavy current from the supply during the peak interval and also cause a large voltage drop in the system due to which the equipment may get damage.
An ac drive is a device that is used to control the speed of an electric motor. The speed is controlled by changing the frequency of the electrical supply to the motor. The three-phase voltage in the national electrical grid connected to a motor creates a rotating magnetic field in it.
Artwork: Regenerative braking in a nutshell: Top: When you drive an electric vehicle, energy flows from the batteries to the wheels via the electric motor. Bottom: When you brake, energy flows from the wheels to the batteries via the motor, which works as an electric generator.
When the conventional vehicle brakes, the energy is lost to heat energy resulting from the friction between the brake pads and wheels. Regenerative braking allows the range of the EV to be extended; however, the efficiency of capturing this energy is reported to vary from 16% to 70% (Boretti, 2013).
It is braking because it also serves to slow the vehicle. It is regenerative because the energy is recaptured in the battery where it can be used again. In the Tesla Roadster, regenerative braking recovers some energy that would otherwise have been wasted in the brakes.
Which of the following is the best braking method? Explanation: Braking methods based on friction, electromechanical action, eddy-currents, etc. are independent of the motor but sometimes electric braking is better justified owing to its greater economy and absence of brake wear. 2.
This system is called regenerative braking. At present, these kinds of brakes are primarily found in hybrid vehicles like the Toyota Prius, and in fully electric cars, like the Tesla Roadster. In vehicles like these, keeping the battery charged is of considerable importance.
Regenerative braking uses an electric vehicle's motor as a generator to convert much of the kinetic energy lost when decelerating back into stored energy in the vehicle's battery. It takes the inefficiency of braking and simply makes the process less wasteful.
In single stage electric braking method, the braking and energy regeneration are achieved by the use of single stage bidirectional DC/AC converter which is used to drive the BLDC motor. The BLDC motor driven by a single stage bidirectional converter is shown in Fig. 1.
In a battery-powered electric vehicle, regenerative braking (also called regen) is the conversion of the vehicle's kinetic energy into chemical energy stored in the battery, where it can be used later to drive the vehicle. It is braking because it also serves to slow the vehicle.
It limits regenerative braking, so the car recoups less power and drivers can't rely on one-pedal driving. And charging, particularly fast charging, will be limited to protect the battery.
Types of Braking Systems and Types of Brakes
- Hydraulic braking system: This system runs on brake fluid, cylinders, and friction.
- Electromagnetic braking system:
- Advantages of Electromagnetic braking system:
- Servo braking system:
- Mechanical braking system:
- Types of Brakes:
- DISC BRAKE.
- DRUM BRAKES.
Types of braking systems
- Hydraulic braking system: This system works on brake fluid, cylinders, and friction.
- Electromagnetic braking system: Electromagnetic braking systems can be found in many new and hybrid vehicles.
- Servo braking system: Also known as vacuum or vacuum assisted braking.
Brake Requirements:
The brake must be strong enough to stop the vehicle within minimum distance. It is inversely proportional to brake efficiency and proportional to square of speed. Provide good control over vehicle during emergency braking and vehicle must not skid.Dynamic Braking
It is termed "rheostatic" if the generated electrical power is dissipated as heat in brake grid resistors, and "regenerative" if the power is returned to the supply line.A brake is a mechanical device that inhibits motion by absorbing energy from a moving system. It is used for slowing or stopping a moving vehicle, wheel, axle, or to prevent its motion, most often accomplished by means of friction.
Dc motor (Ma) and induction motor (Mc) are currently manufactured and used in 105 N tram drive, their parameters are available. Dc motor (Mb), brushless motor (Me) and slip-ring motor (Md) pa- rameters have been determined by analysis. length should be equal to lm 6 = mm.
AC traction for locomotives is a major improvement over the old DC systems. The primary advantages of AC traction are adhesion levels up to 100% greater than DC and much higher reliability and reduced maintenance requirements of AC traction motors. 45 for old DC units to about . 90 for modern AC units.
The synchronous motor has been used in electric traction - the most well-known application being by the French in their TGV Atlantique train. This used a 25 kV AC supply, rectified to DC and then inverted back to AC for supply to the motor.
Single Phase AC Traction System
In this type of traction system, AC series motors are used to produce the propulsion of vehicle. This system uses AC voltages from 15-25KV at a frequency of 16.7 (i.e., 16 2/3) or 25 Hz. This low frequency leads to give better performance and more efficient operation by the series motor.The wheel of Locomotives are driven by Traction Motors through gears. Thus the speed of Locomotives is controlled by controlling the speed of Traction Motor. Earlier DC Series Traction Motors were used. Its speed was controlled by varying the voltage applied across this Traction Motor.
A very important factor in traction drives, Coefficient of Adhesion in Traction (μa), provides a quantitative measure of the tendency of wheels to slip and is defined as: Weight on the driving axles is also the weight on driving wheels. It is also known as adhesive weight.
