SPICE simulation with Proteus of a coils Tester.

SPICE simulation with Proteus of a Coils Tester.

Ing. Cristoforo Baldoni

This article deals with the Proteus simulation (version 7 and higher) of a low cost and very useful coils tester, easy to build by yourself. It ‘s the In-circuit LOPT (Line OutPut Transformer) Tester by Bob Parker that allows to evaluate the smooth functioning of a coil by turning on a number of different colored LEDs. It doesn ‘t measure the inductance value of a coil, but rather the ratio of its resistive part and the inductive part. This tester is very useful in finding coils with shorted turns, and wound components like yoke windings and SMPS transformers. Low loss components, will turn on four or more LEDs, while components with short circuits will turn on few or no LEDs. We ‘ll se how to implement and simulate with Proteus the circuit which consists of three sections: the low frequency pulse generator, the ring amplitude comparator and the LED bargraph display. We ‘ll se how to model a coil and try different values for the inductive and resistive component to validate the simulation. The Proteus simulation files of the device are available for download after accessing this article.

 

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Circuit-breaker SPICE model

Circuit-Breaker Model for Over-Current Protection Simulation of DC Distribution Systems.

T. ROBBINS
TELSTRA RESEARCH LABORATORIES
BOX 249 ROSEBANK MDC, CLAYTON VICTORIA 3168, AUSTRALIA
Email: t.robbins@trl.oz.au

 

Abstract: This article describes an electrical model of a thermalmagnetic circuit-breaker that can accurately simulate characteristic behaviour over a wide range of overcurrents, including operation in the magnetic region. The model has been validated against measured waveforms from both a high-current DC test facility and a distributed power system rack. The circuit-breaker model can be coupled with other distribution component models to simulate the protection performance in telecommunications DC distribution systems.

 

1.Introduction

The design and analysis of over-current protection for telecommunication DC power systems can be greatly assisted by the use of a computer-aided simulation tool. However, a simulation is only as accurate as the component models and element values used to represent the real world. This article reports on the development of a circuit-breaker model that can accurately represent circuit-breaker behaviour over a wide range of overcurrents.

The performance of protection, distribution and storage devices significantly affects both the reliability and safety of the DC power system. Voltage excursions caused by an over-current instance can cause electronic equipment to malfunction due to over-voltage, and disrupt service due to under-voltage. Poor discrimination between protection devices can cause upstream device operation, resulting in major interruption to service. The rapid advancement of both computing power and analogue circuit simulation programs derived from SPICE software provides a relatively user-friendly environment for over-current protection design and analysis. This is advantageous as telecommunications power distribution systems are often large and complex, and developing an equivalent circuit model for a power system is not a trivial task.

The circuit-breaker model described in this article implements the enhanced modelling functions available with PSpice’s Analog Behavioural Modelling to include circuit-breaker current, time and arcing dependent characteristics. This model complements and extends previously published modelling work [1-2] by Telstra Research Laboratories on other power system components.

 

2.Circuit-Breaker Characteristic Operation

A typical thermal-magnetic circuit-breaker operates (trips) in two distinct modes; the thermal mode occurs for device currents from 1 up to about 10-15 times the rated setting current, and the magnetic mode occurs for all current levels above the thermal operating region. Characteristic current-time curves for the device operating in the thermal region can be approximated by an equation where i n t equals a constant, whereas in the magnetic region the operating time (typically <20ms) is not well defined in device data curves and specifications, as test circuits are based on rectified AC power sources which have typical rise times exceeding a few milliseconds.

The circuit-breaker model presented in this paper has been developed for a 125A moulded device (10kA fault rating), which is commonly used to protect individual battery strings within Telstra’s distributed power supplies.

For device operation in the thermal region, the characteristic i n t form of the current-time curve can be obtained from the device specification curve as shown in Figure 1. A value of n = 3.5 gives an adequate fit over the range of currents within the thermal operating region.

Fig.1 125A circuit-breaker current-time operating boundary curves (courtesy of GEC ALSTHOM AUSTRALIA).

Fig.1 125A circuit-breaker current-time operating
boundary curves (courtesy of GEC ALSTHOM
AUSTRALIA).

 

 

For device operation in the magnetic region, characteristic current-arc voltage-time behaviour has been observed for the circuit-breakers operating in a high-current DC test facility over a range of current levels and circuit time constants. At the start of such a fault instance, the current passing through the closed circuit-breaker contacts increases to a level where magnetic activation forces the contacts to open. As the contacts start to open an arc is developed which is inherently unstable and a complex voltage-current characteristic occurs as the arc progresses through to extinction.
For the 125A circuit-breaker operating in the magnetic region, the contacts are forced open when the current level typically rises above 2-4kA. Circuit-breaker operation was measured over a range of circuit conditions, such as:

· fast rates of current rise exceeding 10kA/ms, which resulted in short pre-arcing times of about 0.15- 0.2ms (eg. results from a test circuit with 5.4kA prospective current and 0.26ms time constant are shown in Figure 2).

· high prospective current levels exceeding 10kA, which result in pre-arcing times around 0.9ms for circuit time constants of about 1.2ms, as shown in Figure 3. It should be noted that special oscilloscope probing and current shunt techniques are required to record clean waveforms in the high transient noise environment that occurs in a high current test facility.

Fig.2 Measured current and voltage waveforms for a 125A circuit-breaker operating in 54VDC test circuit with 5.2kA prospective current and 0.25ms prospective time constant; 1kA/div current, 20V/div voltage and 0.5ms/div.

Fig.2 Measured current and voltage waveforms for
a 125A circuit-breaker operating in 54VDC test circuit
with 5.2kA prospective current and 0.25ms prospective
time constant; 1kA/div current, 20V/div voltage and
0.5ms/div.

Fig. 3 Measured current and voltage waveforms for a 125A circuit-breaker operating in 54VDC test circuit with about 12kA prospective current and about 1ms prospective time constant; 1kA/div current, 50V/div voltage and 0.5ms/div.

Fig. 3 Measured current and voltage waveforms for
a 125A circuit-breaker operating in 54VDC test circuit
with about 12kA prospective current and about 1ms
prospective time constant; 1kA/div current, 50V/div
voltage and 0.5ms/div.

FuseCircuit-breaker Model

Fuse Model For Over-Current Protection Simulation of DC Distribution Systems.

T. Robbins
Telecom Australia Research Laboratories
770 Blackburn Road, Clayton, 3168
Australia

 

Abstract: The design and analysis of over-current protection for telecommunication DC power systems can be greatly assisted by the use of a computer-aided simulation tool. This article reports on the development of a fuse model for SPICE derived software that can accurately represent characteristic fuse parameters. The fuse model can also be adapted to represent the operation of circuit breakers.

 

1.Introduction

The design and analysis of over-current protection for telecommunication DC power systems can be greatly assisted by the use of a computer-aided simulation tool. However, a simulation is only as accurate as the component models and element values used to represent the real world. This article reports on the development of a fuse model that can accurately represent fuse characteristics. The fuse model can also be adapted to represent the operation of circuit breakers.
The performance of over-current protection devices significantly affects both the reliability and safety of the DC power system. Voltage excursions resulting from the operation of a fuse during a short circuit can cause electronic equipment malfunction due to over-voltage, and disrupt service due to under-voltage. Poor discrimination between protection devices can cause upstream device operation, resulting in major interruption to service.

The rapid advancement of both computing power and analogue circuit simulation programs derived from SPICE software provide a user-friendly environment for over-current protection design and analysis. This environment is advantageous as telecommunications power distribution systems are often large and complex, and developing an equivalent circuit model for apower system is not a trivial task.

The analysis of DC distribution systems using computer simulation has been shown to provide fair agreement between simulated and experimental results [1,2,3]. However, the fuse models developed have not been able to accurately represent fuse characteristics. Typical parameters for a fuse operating in a circuit with a given time constant and prospective current are rated current ir, peak current ip, pre-arcing time tp, arcing time ta, total operating time tt= tp + ta, pre-arcing i²t (i²t)p, arcing i²t (i²t)a and total operating i²t (i²t)t= (i²t)p + (i²t)a. Figure 1 illustrates some of these parameters. The prospective current for a circuit is the maximum current that would be reached if the fuse did not operate.

The i²t or current-squared time rating is a commonly used fuse characteristic when operating current levels are much higher that the rated fuse current ir. The circuit time constant defines the ratio L/R, where L and R are the effective circuit inductance and resistance components in series with the fuse and energy source.

 

 

Typycal fuse parameters

Fig 1. Typycal fuse parameters

A fuse model is developed in Section 2 and model validation is undertaken in Section 3. Section 4 discusses the development of other DC power system component models for application to the analysis of over-current protection, and the paper is summarised in Section 5.

Power supply Control loop

Straightforward Method to Design and Simulate with SPICE the Loop Compensation Controller for All Switching Power Supplies.

Ing. Cristoforo Baldoni

In this article we ‘ll see how to find the output power stage transfer function H(s), called the Control-to-Output function,  of the most switching power supplies: BUCK, BOOST, BUCK-BOOST, HALF-BRIDGE, FULL BRIDGE, both in voltage mode control and current mode control. In spite of the complexity of the different types of power supplies that use one or more output feedback, the output power transfer function H(s), can be reduced to a few schematic categories of general validity. We’ ll see when it’s the case to consider the effects of the RHPZ, the Right Half Plane Zero, and what it means in practical terms.
Once the components for the specific power supply have been sized, we can estimate with good approximation the transfer function which describes mathematically the output power stage. As seen in the article about the determination of POLES and ZEROS by inspection,  we ‘ll identify immediately the POLES and ZEROS which characterize the different switching categories.
We ‘ll draw the Bode plots of these functions with PSpice, and, according to their characteristics, we ‘ll choose the most suitable compensator G(s), implementing the compensation network with the operational amplifiers embedded in the microcontrollers. The SPICE simulation of the open loop transfer function G(s)*H(s), will allows us to evaluate the results for the system stability. Finally, we ‘ll apply this method in two real switching power supply: a low power flyback converter and an off-line, half-bridge switching.
This method allows us to speed up the design of the compensator G(s) in the prototyping phase before the physical measurement with the instrumentation.

It’s strongly recommended the reading of these articles:

Accessing this article you can download the following SPICE simulation files about switching power supply compensation design:

-Forward function example

-Flyback function example

-Flyback function example with a Right Half Plane ZERO

-Origin POLE compensator

-Origin POLE Transfer function implementation

-Forward function compensated example

-One ZERO two POLES compensator

-One ZERO two POLES Transfer Function Implementation

-Flyback with RHPZ compensated

-Three POLES two ZEROS compensator

-Three POLES two ZEROS Transfer Function

-Transfer function of a real Flyback converter

-Compensator for the flyback converter

-Overall compensated  transfer function of the flyback converter

-Transfer function of a real Forward converter

-Compensator for the Forward converter

-Transfer function of compensator for the Forward converter

-Overall compensated  transfer function of the Forward converter

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GPM-SurgeGenerator_page3_image4

SPICE simulation of a Combo Wave Generator.

Thanks for this article to ssleandro

 

In this article we ‘ll se how to implement a template for a Combination Wave Generator that can be a Surge Generator, a Line Impedance Stabilization Networks (LISN), motor control, ripple current, etc. This model can be very useful for hardware engineers which can utilize it in their projects to speed up project development. The platform used for the simulation is PSpice but
it can easily replicated in other SPICE simulation software.

 

The simplified model of the GPM consists of an High-Voltage source U, a charging resistor Rc, an energy storage capacitor Cc. This part of circuit is connected by a switch to 2 Pulse duration shaping resistors Rs, an impedance matching resistor Rm and a Rise time shaping indutor Lr, as in the picture below

 

 

GPM-SurgeGenerator_page3_image1

 

typical values of this components are:  Cc=7.76μF,  Rs1=14.8 Ohm,  Rm=1.05 Ohm,  Lr=9.74μH,  Rs2=23.3 Ohm. The peak voltage on Rs2 can be 1KV, 2KV,..6KV.

 

In the following schematic we set the high voltage with the initial condition of the CapacitorCc, for example for 6KV, we set 6300 in the PSpice IC field of the Cc component. We can adjust the time in U1 to make surge hit at 90/270 degree or whatever phase we want.

 

GPM-SurgeGenerator_page4_image1

 

GPM-SurgeGenerator_page4_image2

 

 

Calibration of Surge Generator.

The IEC/EN 61000-4-5 standars requires the following waveform of open-circuit voltage with no Coupling/Decoupling network (CDN) connected

 

GPM-SurgeGenerator_page5_image1

 

This is the result of the simulation that shows a voltage waveform that fullfills requirementof IEC/EN 61000-4-5

 

GPM-SurgeGenerator_page5_image2

 

 

Below the image of the waveform of short-circuit current with no CDN connected

 

GPM-SurgeGenerator_page6_image2

 

and here again the simulated results:

 

GPM-SurgeGenerator_page6_image1

 

Ipeak is about 1.5KA, T1 is 8uS and T2 is 20uS. The effective coupling impedance is 2Ohm. The simulated current waveform fulfills requirement of IEC/EN 61000-4-5 standards.

OvenExample

Designing and Simulation of Industrial PID Controllers using Microcontrollers

Ing. Cristoforo Baldoni

In this article we’ll see how to pass from the design of analog PID controllers for continuous-time systems to digital controllers, replacing operational amplifiers, resistors and capacitors with microcontrollers. Digital controllers are very compact, all the controller fits on a chip, including the A/D and the D/A converters, moreover, digital controllers are not affected by the aging of the components and don’t change their values with the temperature as analog components do. We’ll see how to apply the Z-transform, the equivalent of the Laplace transform, but for discrete-time systems, we’ll see how to identify the transfer function of a process and we’ll explain, with a step by step procedure, how to apply the theoretical knowledge learnt by examining an Proteus microcontroller based project, that uses its PWM output to control an oven ‘s temperature. The microcontroller has a 10 bit A/D converter. This procedure can be easily adapted with minimal adjustments to other processes to control.

Topics

 

1. Digital Control-System Block Diagrams

 

2. Linear difference equations, Z-Transform, Inverse Z-Transform and Discrete Transfer Function.

 

3. Sampling and A/D Analogic to Digital Converter

 

4. D/A Digital to Analogic Converter and ZERO ORDER HOLD  (ZOH) : Relationship between the Continuous Transfer Function and Discrete Transfer Function of a sampled Process.

 

5.  Block Diagram Manipulation of Sampled Data Systems

 

6. Methods for designing Digital Controllers, Stability.

 

7. Designing  PID controllers by microcontrollers

 

8. Transfer Function Identification and PID Tuning using the Ziegler–Nichols Method.

 

9. Practical case of a temperature control system implemented with a microcontroller PIC and simulated with ISIS Proteus: Step by step explanation of how to apply the theoretical knowledge for implementing and simulating a PID controller.

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polesnetworkBig

Find Poles and Zeros of Circuit by Inspection

 Ing. Cristoforo Baldoni

 

In this article we ‘ll see how to recognize the number of poles and zeros of a transfer function simply by inspection, also of a large linear network, avoiding to calculate the analytical expression of the transfer function.  After reading this article, you ‘ll be able to determine the number of poles at first glance . Once set the output, you ‘ll also be able to determine the number of zeros by inspection and calculate the exact symbolic transfer function, the exact values of zeros and poles with simple software tool available for free. Using the SPICE analysis, we ‘ll verify the results found. The purpose of this article is to explore the concept of poles and zeros of a transfer function, their phisical meaning, and provide useful analysis tool for analog circuit designers and control systems engineers.

 

How many poles has the following network?

 

polesnetworkBig

and what about this High-Pass filter?

fiveorderHPfilter

if your answer to the first question is 9 or 8 , or you don’t recognize a fifth order filter (five poles) in the filter’s picture you should read this article.

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Sumblock

Control System Theory and SPICE Simulation

Ing. Cristoforo Baldoni

This article provides the principles for the design and analysis of Feedback and Control Systems. The Control Systems are everywhere in the modern industrial technological world, in the laser positioning of a CD Reader,  in the very high precision positioning system of an hard disk head, and even our body has a large number of biological control systems. After introducing the basic concepts, we’ll see how easily evaluate the Open loop Transfer Function with PSPice.

 

Topics

 

1.  Processes, Open Loop and Closed Loop Control Systems (Feedback Systems)

 

2. Generic closed loop schematic of Feedback Systems

 

3. Physycal Processes Modeling, differential equations and calculations simplification with Laplace transform

 

4. Transfer Function, Poles and Zeros of a Transfer Function, phisical meaning

 

5. Natural and Forced Response, calculating Residues, when it’s possible simplify identical Zeros and Poles, dominant poles

 

6. Process Stability

 

7. Steady State Error, Type of Systems

 

8. Study of Transfer Function with Bode diagram. Study the Open Loop Transfer Function with SPICE.

 

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opampschematic

Getting Started with PyOPUS

PyOPUS is a Python based platform for very sophisticated circuit optimization and simulation automation. The use of the Python library with the simulator requires a previous SPICE OPUS installation, then refer to the relative tutorial before proceeding. Below we show how to install PyOPUS on windows 7 (64 bit). All the softwares are 32-bit but they work fine on 64-bit. We’ ll have to install the following softwares:

Python 2.6.4 Programming language
NumPy 1.3.0 Package for scientific computing with Python
SciPy 0.7.1 Python software for mathematics, science, and engineering
MatPlotLib 0.99.1 Python 2D plotting library
wxPython 2.8 Blending of the wxWidgets C++ class library with Python
PyOPUS 0.6 installer the Windows32 PyOPUS installer

All these softwares can be downloaded here

The article refers to the softare versions of the table, but the procedure is the same for the updated versions.

Let’s start with the Python installation

the default destination directory is C:Python26

the full features installation requires about 50MegaByte

after the installation we have to add an enviroment variable: Start/Control Panel/System and Security/System/Advanced system settings, now click on Enviroment Variables button.

add to “Path” variable the value “C:Python26”