M.A. Perez

Dual-tap chopping stabilizer with mixed seminatural switching. Analysis and synthesis

Onload tap changers based on silicon-controlled rectifiers or triacs are widely used to regulate ac voltage. Response time is bigger than half-cycle due to the natural commutation used during the zero-current crossing. N. Burany proposed a commutation method for direct ac/ac matrix converters based on power transistors, or other switches with active turn-off, by permitting a freewheeling current path during commutation. This can be applicable to tap changers and release commutation from the zero-current crossing, thus allowing a faster voltage regulation. This paper presents a new two-tap chopped ac/ac voltage stabilizer with compensating transformer and PWM frequency in the order of 5 kHz based on this kind of commutation. The circuit proposed, resulted from a topology search guided by an iterative analysis+synthesis cost comparative method, fits well to low voltage stabilizers and regulators in the range of 0.1 to 1000 kVA and 1 ms response time. The switching behavior and the input and output filtering is fully analyzed. An exhaustive synthesis study follows, giving the component rates as a function of the equipment specification. This allows an easy equipment cost evaluation. Experimental results with IGBT switches are obtained in a 1 kVA prototype.

Ni-Cd and Ni-MH battery optimized fast-charge method for portable telecommunication applications

The market for portable batteries for telecommunication applications is dominated by the Ni-Cd system. This system is now being substituted by another-the Ni-MH system which avoids harming the environment. This paper presents an optimized fast-charge method for Ni-Cd and Ni-MH batteries used in portable applications. The proposed method performs the following two basic functions: the first determines battery state (detecting deteriorated batteries, analyzing the state of charge and so on); and the second optimizes the charging time, simultaneously guaranteeing a safe fast-charge without negative effects on battery life.

A PSpice model for HPS lamps operated at high frequency

A PSpice circuit model has been developed for the electrical characteristics of high-pressure sodium lamps (HPS). The model is constructed from a two-parameter equation, which is based on a set of two measurements. This model is easily constructed and it is suitable for a preliminary design of electronic ballast. Simulated and experimental results are used to verify the analytical discussions, and an electronic ballast design using the proposed model is presented to further demonstrate its application.

Accurate detection algorithm of battery full-capacity under fast-charge

The expanding number of battery portable products has widely increase the use of sealed NiCd/NiMH batteries. Battery fast-charge (in less than one hour) is very useful but, in fast-charge, cell pressure and temperature increase quickly during overcharging (after the battery reaches full-charge). Usual fast-charge end methods do not avoid the overcharge or they require complex calculation processes. In this paper, a new fast-charge end method is proposed. This method is based on a simple and easily implemented algorithm and it allows us to know accurately and reliably the moment when the battery reaches full-capacity. In this way, a safe fast-charge without negative effects on the effective capacity of the battery and on battery cycle-life is guaranteed.

A New Design of Low-Cost Four-Beam Turbidimeter by Using Optical Fibers

Turbidity is one of most important water quality parameters; turbidity measurement and removal is as important in waters for human use as in industrial processes waters. This paper presents a new low cost, small size and good accuracy turbidimeter based upon the use of optical fibers for light transmission. Design takes advantage of using fibers and, consequently, waterproof protection becomes unnecessary, remote measurement is feasible and high S/N ratio is obtained, decreasing overall uncertainty

A new, reliable and easily implemented NiCd/NiMH battery state estimation method

This paper presents a new and reliable battery state estimation method for Ni-Cd and Ni-MH batteries used in portable applications. The proposed method performs the following two basic functions. The first one determines battery state, detecting deteriorated batteries. The second one guarantees a safe fast-charge without negative effects on battery life, analyzing the previous charge state of the battery. Due to this easily implemented method, effective and universal NiCd/NiMH battery fast-chargers can be obtained by using few and inexpensive components.

Design of a low cost mastitis detector in cows by measuring electrical conductivity of milk

Mastitis in cows is an inflammation of the mammary gland usually caused by bacterial infection of udder tissues. This disease causes considerable damage to the cattlemen whilst reducing the quantity and the quality of the produced milk. An early detection and corrective action can lead to early cure. Although the universal method to measure mastitis levels is by determining the somatic cell counts per milliliter of milk, the electrical conductivity of milk is a rapid test for checking the acceptability of milk to monitor the effects of udder infection. This work presents the design of a low cost mastitis detector in cows using ac conductivity measurements.

A microcontroller-based intelligent fast-charger for Ni-Cd and Ni-MH batteries in portable applications

In portable applications, Ni-Cd and Ni-MH batteries are the most frequently used. In this paper, a new fast-charger is presented for these kinds of batteries, which is able to perform a full-protected charge mode. The control and supervision of the whole process is entrusted to the microcontroller, which that must be able to find out the initial battery state (detecting deteriorated devices), decide the fit way to charge the battery (in order to ensure a long cycle-life) and determine when the charge process must be finished. In this way, the state of the battery is perfectly controlled all of the time, in order to avoid any damage; including those related to an incorrect users operations. The use of a microcontroller has been considered in order to simplify the hardware required (only a few external components are used), and provide a powerful and intelligent tool to undertake, through the programmed algorithm, complex tasks. This paper presents the implementation of this optimized fast-charger and the experimental results obtained.

Direct-evaluation of the fresh-milk somatic cell concentration (SCC) through electrical permittivity measurements

This paper refers to a method and measurement system for the evaluation of the intact somatic cells concentration in fresh cow milk based on the measurement of relative electrical permittivity (/spl epsi//sub r/) of a sample deposited in a systems capacitive cell. The thermal dependence of electrical permittivity had been evaluated and incorporated in a systems measurement algorithm that displays the temperature and somatic cell concentration (SCC) of a sample. Immediate knowledge of the somatic cells concentration in the milk allows cattlemen to associate it with the degree of development of mastitis (infection of the animals mama in general caused by pathogens that penetrate through the teat channel) in cows. It also allows to identify sick animals, to apply the appropriate medical treatment, to separate their milk when it has not the normative demanded quality characteristics, as well as to reduce the milk production losses for this illness in their installation.

Low-cost video-microscopy system for evaluation of fresh cow milk somatic cell concentration

Somatic cell concentration (SCC) is an important indicator in detecting the mastitis infection in cows: SCC is a measure of milk quality. Direct Optical Microscopy is the reference method of SCC evaluation, but it is extremely time consuming, This paper shows the advantageous results of applying a low-cost video microscopy system that evaluates somatic cell concentration in fresh cow milk.