EESA Club Service August 12th Eureka... “I don’t believe in taking right decisions. I believe in taking decisions and proving them right.” – Ratan Tata New on the block… First ‘electric’ road charges buses in South Korea Electric Rail Gun principle • An electrically powered electromagnetic projectile launcher. Construction -A pair of parallel conducting rails -A sliding armature is accelerated. • • • • Mathematical formula: Permeability constant- µo Radius of the rails - r Distance between the centrepoints of the rails-d The current in amps through the system -I B(s)=µoI/(2pi*s) • Materials • Heat dissipation Specifications • • • • • Current required-1MA Power developed-32MJ Speed of projectile-5,400 km/hr Range of projectile-120km Attachable destructive war heads • Applications: 1. Launch or launch assist of spacecraft • As weapons • Tests • Trigger for Inertial Confinement Fusion Take a stab 2 How transformers work...? Varying frequency... Need • Connecting 2 grids operating at different frequencies • HVDC tie Cost and foot print Harmonics produced by power electronic devices Key-Components 1. 2. 3. 4. 5. Its basic working is very similar to a induction machine Rotary transformer High power collector Drive motor Shunt capacitors Conventional transformer 1. Rotary transformer (runkle machine) • core and winding very similar to that of high efficiency 3 phase induction Machines • bar windings and low loss laminated cores • machine design is based on a vertical, air-cooled concept for simplicity and reliability • power transfer by magnetic coupling through air gap 2. High power collector • well proven carbon-brush on Cu slip rings • low speed permits large diameter slip rings to attain adequate insulation while simultaneously providing a substantial surface area for spreading the current among many parallel brushes • Power transferred is 100 MW 3. Drive motor • DC motor • speed below 3 rpm • Why DC motor...? 4. Capacitor bank 5. Conventional transformer Specifications • Langlois and Quebec 315/120 kV substation • 100 MW, 17 kV rotary transformer • 3750HP DC motor and variable speed drive system • three 25 MVAR switched shunt capacitor banks • two 120/17 kV conventional transformers Principle Working • The real power flow through the rotary transformer is proportional to the phase angle difference between the stator and the rotor. • Reactive power flow through the VFT is determined by the series impedance of the rotary transformer and the difference in magnitude of voltages on the two sides. • Power flow is proportional to the magnitude and direction of the torque applied • Torque is applied in one direction, then power flows from the stator winding to the rotor winding • If torque is applied in the opposite direction, then power flows from the rotor winding to the stator winding. • If no torque is applied, then no power flows through the rotary transformer. • the rotational speed will be proportional to the difference in frequency between the two power grids • Regardless of power flow, the rotor inherently orients itself to follow the phase angle difference imposed by the two asynchronous systems Applying basics… • Since the Runkle Machine behaves like a transformer, ampere-turns must balance between rotor and stator • Both the stator and rotor windings link the same magnetic flux. However, the frequency differs so the voltage will also differ by the same ratio • It should be noted that the drive system torque TD is independent of rotational speed, being only proportional to stator current and air gap flux. Since the machine will operate near constant flux, this means that torque is proportional only to stator current. Hence, if the stator frequency is constant, then the torque is proportional to through power. Control and protection • VFT has automated sequences for energization, starting, and stopping. • The control system for the VFT is comprised of digital processors arranged in a modular configuration • The control system also includes a local operator panel, which is a backup to the higher-level operator interface. • The system sends torque and sequencing commands to the standard dc motor drive system • The UVC also includes a local operator panel, which is a backup to the higher-level operator interface. • (HMI) screens • Feedback control • A VFT unit is protected by redundant protection systems, Advantages • It provides a simple and controlled path between electrical grids, permitting power exchanges that couldn't previously be accomplished owing to technical constraints such as asynchronous boundaries or congested systems. • similar conventional HVdc site requiring typically 2 to 3 times that space. • Unlike power-electronic alternatives, the VFT produces negligible harmonics and cannot cause undesirable interactions with neighbouring generators or other equipment on the grid. • When compared to HVdc tie, the primary advantage of the VFT over the is in its lower cost, better technical attributes for the application, smaller site size, and conventional electrical machine design that most operation and maintenance personal are familiar with. • Low maintenance • High reliability • The behaviour obtained during commissioning tests demonstrated that this new technology is an effective way of transferring power between asynchronous systems. Applications • utilize the dual ability to control the phase as well as to compensate for the frequency variation. (wind turbines) • operate pumps or hydro turbines closer to their maximum efficiency conditions • to stabilize or absorb load swings in a power system • Phase shifting transformer From our technical advisor From our President Thank you...