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61-470: The Kawasaki Heavy Industries & Nippon Sharyo (KNS) C751B was the third generation electric multiple unit rolling stock that operated on the North–South and East–West lines of Singapore 's Mass Rapid Transit (MRT) system from 2000 to 2024, manufactured by Kawasaki Heavy Industries & Nippon Sharyo (KNS) under Contract 751B. 21 trainsets of 6 cars each were purchased at S$ 231 million, and it

122-537: A phase converter having single-phase converter input and three-phase inverter output. Controller advances have exploited dramatic increases in the voltage and current ratings and switching frequency of solid-state power devices over the past six decades. Introduced in 1983, the insulated-gate bipolar transistor (IGBT) has in the past two decades come to dominate VFDs as an inverter switching device. In variable- torque applications suited for Volts-per-Hertz (V/Hz) drive control, AC motor characteristics require that

183-557: A VFD system is usually a three-phase induction motor . Some types of single-phase motors or synchronous motors can be advantageous in some situations, but generally three-phase induction motors are preferred as the most economical. Motors that are designed for fixed-speed operation are often used. Elevated-voltage stresses imposed on induction motors that are supplied by VFDs require that such motors be designed for definite-purpose inverter-fed duty in accordance with such requirements as Part 31 of NEMA Standard MG-1. The VFD controller

244-440: A VFD, the stopping sequence is just the opposite as the starting sequence. The frequency and voltage applied to the motor are ramped down at a controlled rate. When the frequency approaches zero, the motor is shut off. A small amount of braking torque is available to help decelerate the load a little faster than it would stop if the motor were simply switched off and allowed to coast. Additional braking torque can be obtained by adding

305-621: A braking circuit (resistor controlled by a transistor) to dissipate the braking energy. With a four-quadrant rectifier (active front-end), the VFD is able to brake the load by applying a reverse torque and injecting the energy back to the AC line. Many fixed-speed motor load applications that are supplied direct from AC line power can save energy when they are operated at variable speed by means of VFD. Such energy cost savings are especially pronounced in variable-torque centrifugal fan and pump applications, where

366-409: A conveyor application for smoother deceleration and acceleration control, which reduces the backlash that can occur when a conveyor is accelerating or decelerating. Performance factors tending to favor the use of DC drives over AC drives include such requirements as continuous operation at low speed, four-quadrant operation with regeneration, frequent acceleration and deceleration routines, and need for

427-402: A fault was detected in a C751B train and it was subsequently withdrawn to Changi Depot for investigations. As the train was under warranty, the engineers from the manufacturers of the train and gearbox were flown in on 21 April. They subsequently detected metal fragments in the gearboxes, and those of another 20 trains. On 23 April 2002, SMRT immediately withdrew all 21 C751B trains and suspended

488-501: A maximum output of 140 kW. The C751B used the monolink axlebox type bolsterless air spring bogie. There are no major technical difference between a trailer and motor car bogie other than additional electrical components for the latter. A break from tradition, the C751B featured auxiliary inverters for its electrical systems on all six cars of the train. Previously, auxiliary inverters are mounted only on motor cars. The VVVF Inverter

549-497: A means for an operator to start and stop the motor and adjust the operating speed. The VFD may also be controlled by a programmable logic controller through Modbus or another similar interface. Additional operator control functions might include reversing, and switching between manual speed adjustment and automatic control from an external process control signal. The operator interface often includes an alphanumeric display or indication lights and meters to provide information about

610-411: A motor) that controls speed and torque by varying the frequency of the input electricity. Depending on its topology , it controls the associated voltage or current variation. VFDs are used in applications ranging from small appliances to large compressors. Systems using VFDs can be more efficient than hydraulic systems , such as in systems with pumps and damper control for fans. Since

671-483: A motor-driving car or power-driving car. On third rail systems, the outer vehicles usually carry the pick up shoes with the motor vehicles receiving the current via intra-unit connections . Many modern two-car EMU sets are set up as twin or "married pair" units. While both units in a married pair are typically driving motors, the ancillary equipment (air compressor and tanks, batteries and charging equipment, traction power and control equipment, etc.) are shared between

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732-406: A pure electrical means of communication. Typical means of hardwired communication are: 4-20mA , 0-10VDC, or using the internal 24VDC power supply with a potentiometer . Speed can also be controlled remotely and locally. Remote control instructs the VFD to ignore speed commands from the keypad while local control instructs the VFD to ignore external control and only abide by the keypad. Depending on

793-534: A step-up transformer is placed between a LV drive and a MV motor load. MV drives are typically rated for motor applications greater than between about 375 and 750 kW (503 and 1,006 hp). MV drives have historically required considerably more application design effort than required for LV drive applications. The power rating of MV drives can reach 100 MW (130,000 hp), a range of different drive topologies being involved for different rating, performance, power quality, and reliability requirements. It

854-436: A wide range of single-phase and multi-phase AC motors. Low-voltage (LV) drives are designed to operate at output voltages equal to or less than 690 V. While motor-application LV drives are available in ratings of up to the order of 5 or 6 MW, economic considerations typically favor medium-voltage (MV) drives with much lower power ratings. Different MV drive topologies (see Table 2) are configured in accordance with

915-546: Is a solid-state power electronics conversion system consisting of three distinct sub-systems: a rectifier bridge converter, a direct current (DC) link, and an inverter. Voltage-source inverter (VSI) drives (see 'Generic topologies' sub-section below) are by far the most common type of drives. Most drives are AC–AC drives in that they convert AC line input to AC inverter output. However, in some applications such as common DC bus or solar applications, drives are configured as DC–AC drives. The most basic rectifier converter for

976-400: Is also often available to allow the VFD to be configured, adjusted, monitored, and controlled using a computer. There are two main ways to control the speed of a VFD; networked or hardwired. Networked involves transmitting the intended speed over a communication protocol such as Modbus , Modbus / TCP , EtherNet/IP , or via a keypad using Display Serial Interface while hardwired involves

1037-596: Is constructed from intersections of a saw-toothed carrier signal with a modulating sinusoidal signal which is variable in operating frequency as well as in voltage (or current). Operation of the motors above rated nameplate speed (base speed) is possible, but is limited to conditions that do not require more power than the nameplate rating of the motor. This is sometimes called "field weakening" and, for AC motors, means operating at less than rated V/Hz and above rated nameplate speed. Permanent magnet synchronous motors have quite limited field-weakening speed range due to

1098-414: Is drawing less than 50% of its rated current from the mains in the low-speed range. A VFD can be adjusted to produce a steady 150% starting torque from standstill right up to full speed. However, motor cooling deteriorates and can result in overheating as speed decreases such that prolonged low-speed operation with significant torque is not usually possible without separately motorized fan ventilation. With

1159-443: Is estimated that drive technology is adopted in as many as 30–40% of all newly installed motors. An energy consumption breakdown of the global population of AC motor installations is as shown in the following table: AC drives are used to bring about process and quality improvements in industrial and commercial applications' acceleration, flow, monitoring, pressure, speed, temperature, tension, and torque. Fixed-speed loads subject

1220-412: Is regarded as the inventor of this technology. Strömberg managed to sell the idea of PWM drive to Helsinki Metro in 1973 and in 1982 the first PWM drive SAMI10 were operational. A variable-frequency drive is a device used in a drive system consisting of the following three main sub-systems: AC motor, main drive controller assembly, and drive/operator interface. The AC electric motor used in

1281-417: Is simpler as no provision is needed for exhausting fumes, although retrofitting existing limited-clearance tunnels to accommodate the extra equipment needed to transmit electric power to the train can be difficult. Multiple unit train control was first used in the 1890s. The Liverpool Overhead Railway opened in 1893 with two-car electric multiple units, controllers in cabs at both ends directly controlling

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1342-779: The China Railway High-speed in China, ICE 3 in Germany, and the British Rail class 395 Javelin. The retired New York–Washington Metroliner service, first operated by the Pennsylvania Railroad and later by Amtrak , also featured high-speed electric multiple-unit cars, known as the Budd Metroliner . EMUs powered by fuel cells are under development. If successful, this would avoid

1403-520: The 1980s, power electronics technology has reduced VFD cost and size and has improved performance through advances in semiconductor switching devices, drive topologies, simulation and control techniques, and control hardware and software. VFDs include low- and medium-voltage AC–AC and DC–AC topologies. Pulse-Width Modulating (PWM) variable-frequency drive projects started in the 1960s at Strömberg in Finland. Martti Harmoinen  [ fi ]

1464-578: The Boon Lay – Changi Airport train through service, replacing it with the Tanah Merah – Changi Airport shuttle service. Train frequencies were also adjusted until 6 May 2002, when 8 trains returned to service. Service resumed on 16 May 2002, with 7 more trains back on service. By end of May 2002, all C751B trains had been returned to service. In December 2019, Toyotron Pte Ltd was awarded the contract for disposal of old SMRT trains. On 28 September 2020,

1525-519: The C751B trains was called on 12 April 1997 together with the opening of Changi Airport extension and to continuously expand the fleet. The contract was awarded to Japanese firms Kawasaki and Nippon Sharyo on 18 January 1998. The first C751B was delivered in August 1999 to Singapore, before entering revenue service in April 2000. The formal launch ceremony was held on 8 May 2000 at Ang Mo Kio MRT Station. It

1586-544: The LTA announced that all C751B trains would be replaced by new Alstom Movia R151 trains, along with the 19 C651 trainsets and the 66 C151 trainsets from 2024 onwards. On 14 March 2021, the first C751B train (set 339/340) was sent for scrap. On 30 September 2024, the final C751B train (set 337/338) made its last run on the North-South Line; it was sent to Tuas Depot for decommissioning on 4 October 2024. These are

1647-463: The United States, an estimated 60–65% of electrical energy is used to supply motors, 75% of which are variable-torque fan, pump, and compressor loads. Eighteen percent of the energy used in the 40 million motors in the U.S. could be saved by efficient energy improvement technologies such as VFDs. Only about 3% of the total installed base of AC motors are provided with AC drives. However, it

1708-426: The VFD controller. Basic programming of the microprocessor is provided as user-inaccessible firmware . User programming of display , variable, and function block parameters is provided to control, protect, and monitor the VFD, motor, and driven equipment. The basic drive controller can be configured to selectively include such optional power components and accessories as follows: The operator interface provides

1769-722: The VSI drive is configured as a three-phase, six-pulse, full-wave diode bridge . In a VSI drive, the DC link consists of a capacitor which smooths out the converter's DC output ripple and provides a stiff input to the inverter. This filtered DC voltage is converted to quasi- sinusoidal AC voltage output using the inverter's active switching elements. VSI drives provide higher power factor and lower harmonic distortion than phase-controlled current-source inverter (CSI) and load-commutated inverter (LCI) drives (see 'Generic topologies' sub-section below). The drive controller can also be configured as

1830-445: The batteries are charged via the electric pickup when operating on electric mode. EMUs, when compared with electric locomotives , offer: Electric locomotives, when compared to EMUs, offer: VVVF A variable-frequency drive ( VFD , or adjustable-frequency drive , adjustable-speed drive , variable-speed drive , AC drive , micro drive , inverter drive , or drive ) is a type of AC motor drive (system incorporating

1891-544: The chart's four quadrants are defined as follows: Most applications involve single-quadrant loads operating in quadrant I, such as in variable-torque (e.g. centrifugal pumps or fans) and certain constant-torque (e.g. extruders) loads. Certain applications involve two-quadrant loads operating in quadrant I and II where the speed is positive but the torque changes polarity as in case of a fan decelerating faster than natural mechanical losses. Some sources define two-quadrant drives as loads operating in quadrants I and III where

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1952-430: The constant magnet flux linkage . Wound-rotor synchronous motors and induction motors have much wider speed range. For example, a 100 HP, 460 V, 60 Hz, 1775  RPM (4-pole) induction motor supplied with 460 V, 75 Hz (6.134 V/Hz), would be limited to 60/75 = 80% torque at 125% speed (2218.75 RPM) = 100% power. At higher speeds, the induction motor torque has to be limited further due to

2013-485: The construction of electric traction railways and trolley systems worldwide. Each car of the train has its own traction motors: by means of motor control relays in each car energized by train-line wires from the front car all of the traction motors in the train are controlled in unison. The cars that form a complete EMU set can usually be separated by function into four types: power car, motor car, driving car, and trailer car. Each car can have more than one function, such as

2074-427: The contactor thus turns on the drive and has it output to a designated speed. Depending on the sophistication of the drive multiple auto-starting behavior can be developed e.g. the drive auto-starts on power up but does not auto-start from clearing an emergency stop until a reset has been cycled. Referring to the accompanying chart, drive applications can be categorized as single-quadrant, two-quadrant, or four-quadrant;

2135-570: The introduction of platform screen doors on elevated stations. The C151A , C151B and C151C sets manufactured by Kawasaki Heavy Industries & CRRC Qingdao Sifang are also developed from the Kawasaki–Nippon Sharyo C751B. All cars were retrofitted with 6 LCD Displays per car and all except trainset 347/348 which featured Visual Passenger Information System displays from July 2001 to September 2009. These used to show rail travel information, commercials and movie trailers . The C751B

2196-420: The load's torque and power vary with the square and cube , respectively, of the speed. This change gives a large power reduction compared to fixed-speed operation for a relatively small reduction in speed. For example, at 63% speed a motor load consumes only 25% of its full-speed power. This reduction is in accordance with affinity laws that define the relationship between various centrifugal load variables. In

2257-418: The lowering of the breakaway torque of the motor. Thus, rated power can be typically produced only up to 130–150% of the rated nameplate speed. Wound-rotor synchronous motors can be run at even higher speeds. In rolling mill drives, often 200–300% of the base speed is used. The mechanical strength of the rotor limits the maximum speed of the motor. An embedded microprocessor governs the overall operation of

2318-433: The model a VFD's operating parameters can be programmed via: dedicated programming software, internal keypad, external keypad, or SD card. VFDs will often block out most programming changes while running. Typical parameters that need to be set include: motor nameplate information, speed reference source, on/off control source and braking control. It is also common for VFDs to provide debugging information such as fault codes and

2379-492: The motor to a high starting torque and to current surges that are up to eight times the full-load current. AC drives instead gradually ramp the motor up to operating speed to lessen mechanical and electrical stress, reducing maintenance and repair costs, and extending the life of the motor and the driven equipment. Variable-speed drives can also run a motor in specialized patterns to further minimize mechanical and electrical stress. For example, an S-curve pattern can be applied to

2440-481: The motor to be protected for a hazardous area. The following table compares AC and DC drives according to certain key parameters: ^ High-frequency injection AC drives can be classified according to the following generic topologies: Most drives use one or more of the following control platforms: Variable-frequency drives are also categorized by the following load torque and power characteristics: VFDs are available with voltage and current ratings covering

2501-433: The motor voltage magnitude, angle from reference, and frequency so as to precisely control the motor's magnetic flux and mechanical torque. Although space vector pulse-width modulation (SVPWM) is becoming increasingly popular, sinusoidal PWM (SPWM) is the most straightforward method used to vary drives' motor voltage (or current) and frequency. With SPWM control (see Fig. 1), quasi-sinusoidal, variable-pulse-width output

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2562-416: The need for an overhead line or third rail . An example is Alstom ’s hydrogen -powered Coradia iLint . The term hydrail has been coined for hydrogen-powered rail vehicles. Many battery electric multiple units are in operation around the world, with the take up being strong. Many are bi-modal taking energy from onboard battery banks and line pickups such as overhead wires or third rail. In most cases

2623-453: The operation of the drive. An operator interface keypad and display unit is often provided on the front of the VFD controller as shown in the photograph above. The keypad display can often be cable-connected and mounted a short distance from the VFD controller. Most are also provided with input and output (I/O) terminals for connecting push buttons, switches, and other operator interface devices or control signals. A serial communications port

2684-553: The outer end of the pair, saving space and expense over a cab at both ends of each car. Disadvantages include a loss of operational flexibility, as trains must be multiples of two cars, and a failure on a single car could force removing both it and its partner from service. Some of the more famous electric multiple units in the world are high-speed trains: the Italian Pendolino and Frecciarossa 1000 , Shinkansen in Japan,

2745-402: The same polarity. In starting a motor, a VFD initially applies a low frequency and voltage, thus avoiding high inrush-current associated with direct-on-line starting . After the start of the VFD, the applied frequency and voltage are increased at a controlled rate or ramped up to accelerate the load. This starting method typically allows a motor to develop 150% of its rated torque while the VFD

2806-435: The speed and torque is same (positive or negative) polarity in both directions. Certain high-performance applications involve four-quadrant loads (Quadrants I to IV) where the speed and torque can be in any direction such as in hoists, elevators, and hilly conveyors. Regeneration can occur only in the drive's DC link bus when inverter voltage is smaller in magnitude than the motor back- EMF and inverter voltage and back-EMF are

2867-404: The states of the input signals. Most VFDs allow auto-starting to be enabled. Which will drive the output to a designated frequency after a power cycle, or after a fault has been cleared, or after the emergency stop signal has been restored (generally emergency stops are active low logic). One popular way to control a VFD is to enable auto-start and place L1, L2, and L3 into a contactor. Powering on

2928-568: The traction current to motors on both cars. The multiple unit traction control system was developed by Frank Sprague and first applied and tested on the South Side Elevated Railroad (now part of the Chicago 'L' ) in 1897. In 1895, derived from his company's invention and production of direct current elevator control systems, Frank Sprague invented a multiple unit controller for electric train operation. This accelerated

2989-440: The train, taking up the space of two seats next to the door at the end of each carriage. Passengers preferred not to use them in favour of theft and were underutilised as people preferred to hold on to their bags in the train. Luggage racks were eventually removed when the through train service to Changi Airport was converted into a shuttle service, and the luggage rack spaces were replaced by extra standing spaces. On 13 April 2002,

3050-559: The trains that are preserved: The configuration of a C751B in revenue service is DT–M1–M2+M2–M1–DT. The car numbers of the trains range from x311 to x352, where x depends on the carriage type. Individual cars are assigned a 4 digit serial number by the rail operator SMRT Trains . A complete six-car trainset consists of an identical twin set of one driving trailer (DT) and two motor (M) cars permanently coupled together. For example, set 349/350 consists of carriages 3349, 1349, 2349, 2350, 1350 and 3350 in this order. As fleet number 301/302

3111-426: The two cars in the set. Since neither car can operate without its "partner", such sets are permanently coupled and can only be split at maintenance facilities. Advantages of married pair units include weight and cost savings over single-unit cars (due to halving the ancillary equipment required per set) while allowing all cars to be powered, unlike a motor-trailer combination. Each car has only one control cab, located at

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3172-691: The voltage magnitude of the inverter's output to the motor be adjusted to match the required load torque in a linear V/Hz relationship. For example, for 460 V, 60 Hz motors, this linear V/Hz relationship is 460/60 = 7.67 V/Hz. While suitable in wide-ranging applications, V/Hz control is sub-optimal in high-performance applications involving low speed or demanding, dynamic speed regulation, positioning, and reversing load requirements. Some V/Hz control drives can also operate in quadratic V/Hz mode or can even be programmed to suit special multi-point V/Hz paths. The two other drive control platforms, vector control and direct torque control (DTC), adjust

3233-421: The voltage/current-combination ratings used in different drive controllers' switching devices such that any given voltage rating is greater than or equal to one to the following standard nominal motor voltage ratings: generally either 2 + 3 ⁄ 4 .16 kV (60 Hz) or 3 + 3 ⁄ 6 .6 kV (50 Hz), with one thyristor manufacturer rated for up to 12 kV switching. In some applications

3294-571: Was already being used by a money train (which was a Kawasaki Heavy Industries C151 ), the C751B trains were numbered starting from 311/312. Electric multiple unit EMUs are popular on commuter, and suburban rail networks around the world due to their fast acceleration and pollution-free operation, and are used on most rapid-transit systems. Being quieter than diesel multiple units (DMUs) and locomotive -hauled trains, EMUs can operate later at night and more frequently without disturbing nearby residents. In addition, tunnel design for EMU trains

3355-690: Was also installed, and all door panels and walls were cream coloured, which is a standard appearance of all SMRT trains. Energy efficient lighting was installed on cars 1328 and 3328 in 2017. The C751B was the second commuter type Electric Multiple Unit (EMU) after the Sanyo 5030 series to feature electric systems fully manufactured by Fuji Electric. Propulsion was controlled by VVVF Inverter with 2-level IGBT semiconductor controller, rated at 415 kVA. Each inverter unit controlled two motors on one bogie (1C2M), and one motor car featured two of such units. Motors were three-phrase AC induction type, model MLR109, with

3416-562: Was also the first train to have wheelchair spaces, with the retrofitting of the elevators in the MRT stations, which also began in 2000. The interior design was also improved; the seats were now 48 cm wide - about 5 cm wider than on previous train types. The STARIS version 2.0 was piloted on train car 3322 in 2010, but it was uninstalled in 2016 as it was not compatible with the updated STARIS displays for C151B and C151C trains. The LCD Displays were deactivated since July 2007 and LED Displays

3477-491: Was controlled by IGBT semiconductors and rated at 80 kVA. A battery charger was built with the inverter and provides 16 kW output. The Kawasaki Heavy Industries & Nippon Sharyo C751B formed the basis for the next three rolling stock generations for the North–South and East–West lines, consisting of the C151A , C151B and C151C sets manufactured by Kawasaki Heavy Industries & CRRC Qingdao Sifang. The tender of

3538-609: Was not used since January 2008 with the change of voice announcer. All VPIS were removed to make way for the STARIS by 2010. In 2013, support bars are added to the seats with hand grips, and the middle handrails with hand grips are configured to join across nearly one car, as such all triplicates stanchion poles are replaced by regular single grabpoles. The colour of the seats on each car of these trains were also different from their earlier counterparts - cobalt blue for M1, turquoise for M2 and magenta for DT. A teal green colour flooring

3599-541: Was the first Singapore's MRT train to be painted in SMRT's "Blackbird" livery. The C751B was also the first MRT train type to feature anti-climbers , which help prevent overriding of the train cab in the event of a collision that could cause a catastrophic failure. They also featured rubber guards to prevent people from falling between cars: this feature was also used on the C151A. However, the rubber guards are now redundant with

3660-509: Was the first rolling stock to feature VVVF insulated-gate bipolar transistor traction control system. Kawasaki manufactured 66 cars and Nippon Sharyo manufactured 60 cars respectively with no comparable differences, having been built to agreed specifications. The front of the train spotted a more slanted and streamlined look, with the run number display in Orange LED Displays supplied by Mobitec MobiLED. The C751B train

3721-694: Was the first train to be painted in the Blackbird SMRT livery since 1998, which was mandated for new and refurbished trains until 2016. These trains were capable of running on both the North–South and East–West Lines at all times. However, they were mostly deployed from 2012 on the North–South Line until 2018 when most trains were moved to East–West Line. With the opening of the Changi Airport Line, several trains were delivered with luggage racks and were installed in every carriage of

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