Specification of A.C. Motors to work in Classified areas

Helpfull tips to considered at the time of making and A.C. Motor purchase order.

Lightining Protection System Design

Guide to design and establish the efective protection zone agains lightings.

Welcome to the website Electrical Engineering and Technology. A place for Modern Science

Our main purpose is presenting information about the latest technology improvements in the fields of electronics and electrical engineering as well as the influence of other science fields that might get involved.

Moreover it will present general interest topics for all people involved in the area day by day, having a simple approach to the subjects that are treated, in order to make it easy for all to understand the deepest topics about electricity , including for those who just have a hint of curiosity and the desire of learning.

Monday, February 29, 2016

Variable frequency driver – Engineer and Installation 1/#

Nowadays, using variable frequency drivers is the most common way to control AC motor´s speed in industries worldwide, looking to avoid DC motors in the system and therefore eliminated the maintenance of the brushes and the expensive control systems.

Once it’s decided to install a VFD in the process whichever it might be, developing engineering for its proper installation is need, and the following article highlights some of the factors that have to be considered.

In first place is important to have in mind during the engineering process that the installation can be one of the two following:

1. The VFD will be installed with a motor that has been design to run with a VFD. The article will focus on this option.

2. The VFD will be installed with an old motor that used to run without speed control, and it was not design to work with a VFD. Considerations in this case will be analyzed in an up-coming article.

For the first case New Motor – New VFD, the following points shall be taken under consideration:

1. Location of the VFD.

2. Distance from VFD to Motor (total wiring route).

3. Type of cable from the VFD to the motor.

4. Kind of wiring installation.

5. Installation of control wiring.

6. Electrical protection against short-circuits and terminal overload.

7. Harmonics generated by the VFD.

8. Effects of reflected waves.

9. High frequency Foucault currents between the motor and the pump or compressor.

10. VFD autonomy when faults in the main power feeder.

1. Location of the VFD.

A VFD is an electrical equipment with electronic components that generate a lot of heat, therefore it has to be notice that the VFD should have internal fans to help the refrigeration, the environmental conditions play a key factor in the engendering process for this matter.

2. Distance from the VFD to the Motor.

The distance in this case is no relate to the voltage drop that it produces, it is suppose that the cable has been selected accordingly to this considering the distance and the installation type. In this case is important to be aware of the distance in order to eliminate any reflections in the tension wave, which may be present as a result of long distances between VFD and Motor. The distance from the VFD and the motor (wiring distance) should be always informed to the manufacture, depending on the technology used, filters may be needed in the arrangement.

3. Cable used to feed the motor

There are several literatures regarding this matter, at the same time some manufactures design cables to be used exclusively with from the VFD to the motor and is one of the most expensive items in the project.

The cable that goes from the CCM to the VFD can be a regular cable. The cable that goes from the VFD to the motor have to be special for the application, further analysis on this subject will be presented.

Control the AC motor speed using a VFD is something that has become more frequent over time. Let’s reason the cable design more suitable to avoid the troubles that come with it, the manufactures usually present this information to the client but sometimes are not considered as a result of negligence or ignorance of the actual problem.

4. Power Cable Wiring

The cable should be installed apart from other feeders of the system. Different VFD cables to motors can be installed in the same route. It is recommended that the cable from the CCM to the VFD, VFD to Motor and control cables are installed separately.

It’s important to avoid that the cable to the motor goes parallel to other cables for long distances, this to avoid electromagnetic interferences produce by changes in the voltage at the VFD.

If the control cables and the power cables have to crus at certain point, be sure that they do it with an angle of 90 degrees from each other.

The air way trays shall have a good electrical connection between them and respect the grounding system. It’s recommended to use aluminum air ways to level the potential more efficiently

5. Selection and routing of control cables

Similar to the power cables they should go through separated routes.

All control cable shall be shield.

Shall be used a twisted par with double shield cable for analog signals. This kind of cable is also recommended for the signals of the pulse generator. Use an individual pair for each signal. Do not use a combined return for different analog signals.

The best alternative for low voltage digital signals is a cable with double shield, but a several cables with simple shield can also be used.

Analog and digital signals should be transmitted through separated shield cables.

The signals controlled by a relay can be transmitted through the same cable used for digital entries, as long as the voltage is less than 48 V. It is recommended that the signals controlled by relay are transmitted using a twisted pair cable.

24 V DC and 115/230 V AC signals never have to combine in the same cable.

See it in Spanish

E.g. Enrique Paradas

Thursday, December 17, 2015

Basics Of Motor Starters And Contactors - Repost

Welcome to this EATON’s guide, which is about starters, devices that control the use of electrical power to equipment, usually a motor. As the name implies, starters “start” motors. They can also stop them, reverse them, accelerate them, and protect them.
Starters are made from two building blocks, contactors and overload protection:
  • Contactors control the electric current to the motor. Their function is to repeatedly establish and interrupt an electrical power circuit.
  • Overload Protection protects motors from drawing too much current and overheating, from literally “burning out.

The Contactors

A contactor can stand on its own as a power control device, or as part of a starter. Contactors are used in applications ranging from the light switch to the most complex, automated industrial equipment.
Contactors are used by electrical equipment that isfrequently turned off and on (opening and closing the circuit), such as lights, heaters, and motors.
Whatever the application, the function of the contactor is always the same: to make and break all power supply lines running to a load. Or, as defined by NEMA, to repeatedly establish and interrupt an electrical power circuit.
We’ll start by talking about the building blocks of a starter: the contactor and overload protection. We will then conclude with a discussion on starters.
Here are the topics that we will cover:
  1. The Contactor (magnetic contactor, how the contactor operates, contact life etc.)
  2. Overload Protection (How motors work, what is an overload?, overload relay, tripping etc.)
  3. The Starter (magnetic motor starter, starter circuitry, types, standards and ratings etc.)
  4. Helping the Customer (NEMA or IEC?, checking the motor nameplate etc.)

Monday, November 23, 2015

Transfer Switch Application and Selection Manual - Repost

This Manual is intended to provide guidance in the selection and application of transfer switch equipment in a variety of power generation situations. Transfer equipment is available in many configurations, all sharing the same basic function, that of providing a means to connect electrical loads to either of two independent power sources.


Thursday, July 30, 2015

How Loud Is a Wind Turbine

Monday, July 27, 2015

Electrical Installation Guide 2015 - FREE Download Now

Designer, Consultant, Contractor, Panel builder, Facility manager, Student, teacher, Standardisation or certification experts. we all have to know and comply to electrical installation standards and regulations, in order to ensure the safety (and more and more the energy efficiency) of our customers' electrical installations. 

These international standards, set by the IEC, are complex and keep evolving; as a result, we struggled to stay informed.
As an example, are you aware that the IEC 60364 "Low-voltage electrical installations" part 4-42 "Protection for safety - Protection against thermal effects" has been updated in 2014, and that in particular it now includes recommendations for arc fault protection? 
- in premises with sleeping accommodations; 
- in locations with risks of fire due to the nature of processed or stored materials 
In a.c. circuits, the use of arc fault detection devices (AFDDs) in compliance with IEC 62606 will satisfy the above-mentioned recommendation." 

The technology also evolves, which may impact the way we design installations: as an example, LED lighting is increasing its share very fast, and as you know the LED lamps electrical characteristics and behavior (at startup in particular) require special care to be taken when choosing the related control and protection devices. And there is nothing worse than a customer site where the lighting circuit breakers may trip, or where the contactors may face welding of contacts, requiring urgent and costly on-site intervention.

Fortunately, experts in the field from Schneider Electric got together in order to update the Electrical Installation Guide (EIG), a free and complete guide about electrical installations and the related standards. 

Edited since several dozen years, it is a reference work which helps you understand and comply to the IEC standards to be applied in 2015. Thanks to this free and simplified guide, you'll ensure the reliability of your commercial, industrial, or domestic electrical installations. 

What's new or updated in 2015 edition of the Electrical Installation Guide? 
An updated list of relevant IEC standards, new content about LED lighting, new content about Arc Fault Detection Devices (AFDD), some updated chapters about "connection to the MV utility distribution network" and "MV and LV architecture selection guide for buildings", and also some updated examples of Energy Management architectures. 

The content of the Electrical Installation Guide (2015 version) is clear and practical; there's no other guide of that stature! 

The paper version costs 60€ but we propose you to DOWNLOAD the EIG 2015 right NOW and FOR FREE by clicking on the button below:

Thursday, July 23, 2015

How does a Transformer work ?

I will be uploading from now on material that I find explain electrical principles in the easiest understanding way so my readers find it all in just one place.

Hope you learn something once again.

Buchholz Protection for Transformers

The Buchholz protection, protects the transformer again every abnormal phenomenon produce inside the tank. It bases in the fact that the irregularities in the transformer functioning cause heating in the winding and in consequence the production of gases from the oil, the quantity and speed of its production increases at the time the damage spreads. 

The gases that are produce inside the tank go up through the tube in which the relay is installed and they get trap in it.

Disposition of the relay is shown in the scheme 2. The relay box is filed with oil and it contains the floats a1 and a2. When ever little gas bubbles are produce, this elevate from the transformers tank to the oil tank and get trap in the relay, in it the level of oil drops progressively. The top float inclines and when the amount of gases is sufficient, it causes contacts c1 to close and activated the alarm circuit.

In the cases that no measure is taken given the alarm or given the failure the amount of gases is high, the second float drops closing a2 causing the main transformer circuit breaker to open. If a electrical arc is produce inside the transformer, a violent flow of gases will go to the oil tank and c2 to will close suddenly preventing important damage to the transformer.        

Over the top of the relay is a faucet b1, that allows gasses to scape. another faucet b2, allows to prove that the floats and contacts are in good shape.

The relay detects shorcircuits between windings, core and core - windings, phase interruption, excessive overload, oil leak etc. The great advantage of this relay is its high sensibility to warn deterioration or incipient faults, when the most sensibly protection systems wont be that effective.

The characteristic of the gases trp in the Buchholz relay can give an idea of the type of defect and where it produced. The most simple verification is the combustibility test of the gas.  In case of electric arc the oil decomposes producing acetylene that is flammable.

The color of the gases can give an idea of the nature of the defect.

  • White: Paper destruction.
  • Yellow: Wood destruction.
  • Black or Grey: Oil decomposition.
  • Red: Winding isolation damage.  

      A peephole allows to see the gases, the color have to be seen minutes apart from the moment of the event. 

Wednesday, July 22, 2015

Why AC Power Systems have 3 phases?

I am kind of in a wondering phase right know, it all began with the frequencies and then... this next question WHY 3 PHASES. May be more than one electricity enthusiast that haven't got deep in to it but now is wondering. It is mostly mathematics the explanation, by increasing the number of phases the amount of power that is transmitted gets to a point that it is just not efficient, it gets to complex and expensive.

Lets hear this Senior Transmission Engineer for a moment,  he does why I like the most... get complex subjects explained in the most simple way possible.

Hope you learn something new once again. 

Any subjection for topics... leave it in the comment section.  


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