Locomotive control handbook static voltage regulator free download

Therefore, the excitation control must act to keep generator horsepower demand constant over a wide variation of terminal voltage to run the diesel engine with maximum fuel efficiency. The "electronics excitation system" is a system using semiconductor components. The system controls exciter generator field current; i.

The system provides the function of current limit, voltage limit on the generator and keeps the generator power constant at eight different levels as far as possible at each of the eight engine speeds available. The slightly rising line from the origin of the curve at O volts and O amperes to the point A is known as the IR line.

This represents the voltage obtained at various generator currents with the motors connected, but with the train not yet moving. The current in the motors at stand still is equal to the voltage across each motor divided by the motor resistance. The portion of the curve denoted by line AB is the current limit for the generator.

Currents in excess of the values shown by this line would produce excessive slippage when starting a train and also may cause damage to the main generator and traction motors. Voltage and current to the right of this line would represent a higher load on the diesel engine. If the excitation system were allowed to load the engine in such a manner, the engine speed would drop, because of limit in fuel, resulting in loss of power and controlled operation could not be obtained.

The dotted lines represent the characteristic provided by the excitation system to approximate constant engine horsepower. When this occurs, generator characteristic may be trimmed to meet the desired constant H. P curve by the load control potentiometer actuated by the engine governor. The actual position of each curve is determined by an engine speed signal continually fed to the excitation control. When the engine accelerates from one notch value to the next higher one, the generator current increases smoothly until it reaches a new notch value as the engine gets to the corresponding speed for that notch.

The power transistor functions as a switch and is turned "ON" and "OFF" times per second by pulses generated by the oscillator. The pulse width modulator PWM controls the duration of "ON" time as compared to "OFF" time during each pulse, thus regulating the average current in the exciter field PWM responds to several "feed-back" signals as shown in the block diagram Generator armature current is measured by a special reactor called armature current control reactor ACCR.

Generator voltage is measured by a reactor called voltage control Reactor VCR. Only the greater of the two outputs is used at any one time. When the output of either ACCR or VCR is greater than the reference current, a current is put through the main winding of the pulse width modulator to limit generator excitation. The function generator circuit modifies the output of ACCR in relation to generator voltage to produce the constant horsepower portion of the generator characteristic curve for notch 8.

In the lower notches, the function generator also responds to engine speed to provide the proper separation of the notch curves. The generator is mounted on the traction generator gear box and gear driven from it at a speed proportional to engine speed. Three rheostats are mounted on the face of one card.

One adjusts main generator characteristic and two adjust dynamic braking efforts. The reactor consists of a large busbar, two cores, two ac.

Windings, one single turn dc. It operates from a d-c input voltage from the locomotive battery. This reactor, part of the voltage control reactor card in the excitation panel, is a device about the size of a large pocket watch and enclosed in epoxy.

The reactor consists of two toroidal cores around which an ac. This reactor is used in the excitation system to control rather than to measure. Open navigation menu. Close suggestions Search Search. User Settings. Skip carousel. Carousel Previous. Carousel Next. What is Scribd? Explore Ebooks. Bestsellers Editors' Picks All Ebooks. Explore Audiobooks. Bestsellers Editors' Picks All audiobooks.

Explore Magazines. Editors' Picks All magazines. Explore Podcasts All podcasts. The transistors employed in the present embodiment are types TIP and 2N, respectively. This high switching rate permits smaller inductors which store less energy per cycle , and simpler filter elements for ripple control , to be used. It will be appreciated that other clock signal values may of course be employed. In the illustrated embodiment, the flip-flop 48 is active low.

The flip-flop's clear line provides for an optional shutdown circuit feature. An FET switching transistor is preferred due to its fixed, low ON resistance and its minimal drive requirements. Bipolar transistors, in contrast, tend to require a gate drive current that can exceed the capacity of many logic devices and are therefor less desirable, but may nonetheless be used.

A fixed duty cycle clock can directly drive the switching transistor, replacing any pulse width modulator or other controller needed to regulate standard switched mode power supplies.

This is a most useful feature at high switching frequencies. In the initial half of the conversion cycle, with the switching transistor 46 turned on, the output terminal of inductor 42 is shorted to ground, causing the inductor to charge up from the current source After the magnetic field the inductor dissipates, the diode 44 prevents any energy from returning from the output capacitor.

The diode 44 has no special requirements except that it should be capable of handling the maximum current delivered by the inductive element Typically a Schottkey diode with a low forward drop is used. A Fast Recovery diode would be preferred in high frequency implementations. Most switching converters draw a pulsed input current from the raw supply. This pulsing introduces ripple which can be detrimental to other loads attached to the raw supply.

In the illustrated power supply 10, the controlled current source 20 minimizes this ripple by regulating its input current. The feedback control circuit 60 provides the voltage control signal that is fed back to control the linear regulator The feedback signal is derived from the output of the switching regulator 40 and is first ratioed by voltage divider resistors 62, 64 to one-sixth of its original value.

This signal is provided to the non-inverting input of an op-amp The inverting input is provided a reference voltage--here five volts.

A feedback capacitor 68 connects the non-inverting input to the op-amp output and thereby provides a loop gain that diminishes with frequency.

The output of the feedback loop is connected to resistor 26 of the linear regulator 20 and is used to regulate the current provided from the linear regulator. From the foregoing it will be recognized that the illustrated power supply 10 can provide the excellent regulation qualities of linear regulators while permitting the "boost" operation that is characteristic of switched regulators.

The omission of a complex modulator stage to control the switched regulator and the substitution of a simple linear feedback loop greatly reduces circuit complexity and cost with an attendant increase in reliability. The use of a cascaded linear supply permits over-current protection to be easily implemented. Having illustrated and described the principles of my invention in a preferred embodiment, it should be apparent to those skilled in the art that the invention can be modified in arrangement and detail without departing from such principles.

For example, while the invention has been illustrated with reference to an embodiment in which a switched regulator is cascaded after a linear regulator, it will be recognized that this arrangement may be reversed. In embodiments employing a switched regulator as the first regulator, the output from the linear regulator is used to control the duty cycle or switching frequency of the switching regulator.

Similarly, while the invention has been illustrated with reference to a voltage controlled current regulator, it will be recognized that a variety of other linear regulator topologies can alternatively be employed. Likewise, while the invention has been illustrated with reference to one particular switching regulator, it will be recognized that a variety of switching regulator circuits can alternatively be employed.

In view of the wide variety of embodiments to which the principles of my invention may be applied, it should be apparent that the detailed embodiment is illustrative only and should not be taken as limiting the scope of my invention. Rather, I claim as my invention all such modifications as may come within the scope and spirit of the following claims and equivalents thereto.

I claim: 1. A power supply system comprising a switching power supply serially cascaded after a linear power supply; the linear power supply including a linear regulating device, said linear regulating device presenting a linearly variable impedance through which energy is controllably passed and dissipated as heat to effect regulation;. The system of claim 1 in which the linear regulating device includes a transistor configured as a controlled current source, the magnitude of said controlled current being responsive to the feedback signal.

Kassakian, John G. Schlecht, and George C. Principles of Power Electronics. The voltage and current harmonics that are generated by the power converters can be reduced or minimized with a proper choice of the control strategy. Uncontrolled turn on and off Power Diode 2. Controlled turn on uncontrolled turn off Thyristors 3. Power converter along with its controller including the corresponding measurement and interface circuits, is also called power electronic system.

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