Archive for Electrical

admin | October 14, 2011
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Shocking Facts on Electrical Safety



When it comes to electrical safety, many people in commercial, service and light industrial sectors view their workplaces as low risk environments where their safety is not at risk. Unfortunately, electrical shock accidents in the workplace are increasingly common in all work environments; not just in construction and heavy industrial settings. In fact, between 1997 and 2003 the workplace became the primary environment for electrical shock accidents!

Identifying electrical hazards and effectively addressing them to prevent accidents that could cause injuries and/or property damage is essential. You may have even noticed some of the most commonly occurring electrical hazards in your workplace without recognizing them as such. For example, lights that flicker, switches or receptacles that are warm to the touch, extension cords not rated for the equipment to which they’re connected, frayed or cracked wires, a slight burning odour coming from panels or transformers or equipment such as computers and photocopiers left on for extended periods of time when not in use.

Though these conditions seem relatively harmless, the fact is that they represent a serious risk of electrical shock or fire; a risk that can and should be prevented. How? By taking a common sense approach that includes:

1. Employee Training

Ensure all employees have taken the appropriate safety training relative to the work that they do; a wide range of training in electrical safety is available through the Electrical Safety Authority and other sources.

2. Awareness

In Ontario, any electrical product sold, displayed, or connected to a source of power must be approved by a recognized certification agency. Any electrical product that is not approved by such an agency may be unsafe and could pose a serious electrical shock and/or fire hazard. Inexpensive extension cords are a primary example; many imported items such as these are not certified to Canadian safety standards and should not be used.

3. Inspections

Electrical Inspections are required for all new electrical equipment installations and for the electrical maintenance of existing electrical installations. Ensure that all work is performed by a licensed electrician as mandated by the Ontario Ministry of Labour.

4. Planned Maintenance

Stop trouble before it starts! Plan electrical maintenance checks for all systems including production, HVAC and others; this not only helps to minimize risk it can also minimize costs by reducing emergency electrical services, electrical maintenance requirements and expensive, avoidable repairs.

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admin | October 10, 2011
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A complete summary of Electrical Transformer



Electronic transformers are basically are the transformers which are used in electronic applications. This it is an extremely broad description; as a result there are a lot of types of electronic transformers. Example of category of electronic transformers comprises of, instrument, current, , inverting, signal, high voltage, impedance matching, power, pulse, step-up, step-down, switching or switch mode, and saturable. A number of the earlier types can be separated into more sub-types. Nature of switching transformers take in but not restricted to fly back, “feed forward” converter which also termed as” buck”, and “boost”. The “feed forward” kind takes account of a “push-pull center-tap” and a “half bridge” design. It turns out to be understandable from the previous kind of descriptions that the kind designation of an electronic transformer is firm by its planned application.

Electronic transformers might be further explained based on their fundamental structure and/or structure style. A lot of current transformers are wound on toroidal cores; for this reason the transformer is termed or described to as a toroidal current transformer. A lot of transformer coils are wound on spools or tubes. The transformer core is put in into and in the region of the coil. These transformers perhaps referred to as “bobbin wound” or “tube wound” construction. There are a lot of core shape accessible; E, E-I, U, U-I, Pot, RM, PQ, EP, EFD, and others. Electronic transformers may perhaps be further explained by the technique of mounting and electrical terminations. Transformers rose on printed circuit boards possibly “pin-thru” or “surface mount”. Transformers windings are ended to spools pins. Some transformers comprise of direct wires. These wires in general are referred to as “flying leads”.  

Electronic transformers possibly use to bring in power, convey signals, set up voltage isolation connecting circuits, sense voltage and current level, adjust voltage and current levels, offers impedance matching, and filtering. Lightly weighed down transformers may possibly carry out a number of “inductor-like” task, such as store energy and restrictive current flow.

The majority electronic transformers can be holding up in your hand with no trouble, even in a child’s hand, other than there are a number of too huge to be hold. Due to ever-higher working frequencies, additional electronic transformers are being prepared from ferrite core resources, except a few specific applications make use of additional core materials.

In spite of the lot of types of electronic transformers, their theory of procedure does not be at variance. Electrical task are more often than not alike but design characteristics can be different in certain way. There are number of examples of this transformer they are are; unipolar in opposition to bipolar center utilization, saturating or not saturating, amount of energy storage, guidelines, and transformer impedance.

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admin | August 2, 2011
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Protection of Electrical Installations



When speaking about the protection of electrical installation, the most often meant is the overcurrent protection. This is the protection that must be activated in case of exceedingly high currents in an installation (the currents whose value is higher than expected). It can be achieved using safety fuses, or (automatic) circuit breakers; there are two other names: LS and MCB switches.

The task of that protection is to switch out faulty circuits, and thereby protect the loads that are connected to those circuits, thus preventing the consequences (in the first place thermal overloading of conductors, and fire risk). In new buildings are in dwelling electrical installations almost exclusively used circuit breakers owing to their numerous advantages:

• simple use,

• multiple use (no replacement is needed after operation),

• smaller size,

• increased safety.

There is a large choice of circuit breakers by various manufacturers on the market. Their basic technical characteristics are:

• rated current,

• breaking characteristic,

• short-circuit capacity, etc.

The rated current value of the protection device must provide the best possible overcurrent protection of an installation.

When choosing the breaking characteristics, usually are available B, C and (sometimes) also D – complying with the IEC 60898 standard. For a residential installation the most often used is B characteristic. However, if loads with high starting current are to be connected to that installation, (e.g. angle grinders), C characteristics should be used, because it is more resistant to undesired switching-offs at the start.

The short-circuit capacity is declared by its maximum current. A circuit breaker (according to requirements of the standard) must be strong enough to break a circuit three times, and still preserve specific technical characteristics required.

The values, marked on the products, are: 3.000, 4.000, 6.000 and 10.000 A. It is true that usually in housing installation the actual short-circuit currents are lower. But for sure a circuit breaker which is able to break three times 6.000 A, can still more times break lower short-circuit current than a circuit breaker which is declared to be able to break three times 3.000 A. That’s the reason why in some countries (e.g. Germany) the installation of circuit breakers with the short-circuit capacity under 6.000 A is not allowed; so one must be careful when choosing a circuit breaker, it isn’t recommendable to choose circuit breakers having the lowest short-circuit capacity, which is, of course, the cheapest. In addition, neither should be ignored the quality sign on products (e.g. VDE, KEMA and the like), because it ensures the product has been submitted to an appropriate type test.

For single-phase circuits single-phase (single-pole) circuit breakers are used, and for three-phase circuits – three-pole circuit breakers that are specially produced and calibrated by the manufacturer. Therefore composition of three-pole circuit breakers using three single-pole devices is not an adequate solution, and “in the field composed” circuit breaker doesn’t ensure all technical characteristics prescribed.

The second type of protection for an electric installation is protection against electric shock, i.e. against harmful effects of electric current on human body. Three levels of such a protection are known:

• protection against direct contact,

• protection against indirect contact,

• additional protection by using high-sensitive protection switches.

Since the safety is more and more important, for better protection of humans and animals and better fire safety is steadily being developed and perfected a third level – additional protection. The matter concerns the use of so-called residual current circuit breakers (old names for these protection devices are: current protection switches, FI & FID switches, and abbreviations RCCB, RCD). Additional protection for people and animals is enabled only by high-sensitivity protective switches of 30 mA or less. The protective switches with sensitivity of 100 mA are suitable only for fire protection, whereas protective switches with sensitivity of 300 or 500 mA are only convenient to be used as main protective switches.

The residual current circuit breakers are recommended wherever the risk of electric shock is increased: in bathrooms and other humid and wet rooms, nurseries and workshops, where portable electric tools are often used. Needless to say that their use is much expanded in hospitals, kindergartens and schools. The residual current circuit breakers can be used in all installation systems where null and protective conductors are separated. In old electrical installations where so-called nulling is still used such protective switches cannot be used.

Both types of protection: against overcurrent and against electric shock can be combined into one single protective device, named residual current circuit breaker with overcurrent protection (other names for this device: combined protective switch, FI/LS switch, RCBO). These devices include technical characteristics that are a combination of characteristics of both previous protective devices(rated current, breaking characteristic, short-circuit capacity, current sensitivity, etc.). By means of such a device a full-scale protection of electrical installations in a room can be achieved.

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