Impressive Efficiency Results obtained during tests conducted by PM Generators Ltd.

PM Generators Ltd. is best known for its world class permanent magnet alternators and best quality products. PM Generators Ltd. has further taken steps to maintain their competency in the industry by conducting efficiency tests the results of which continue to prove that PMGL manufactures the most efficient products in the industry.

Need of the tests

PM Generators Ltd.  makes sure that only the best products are manufactured at its facility. For this purpose it conducts research and development of newer designs with increased efficiencies and better outputs. Similar tests were conducted to test the efficiencies obtained at varying speeds for a recently built permanent magnet alternator. These alternators are perceived as the future of renewable energy generation. Hence it is all the more important to develop more efficiency in this field.

How were the tests conducted?

We know that efficiency is output by input in terms of percentage. For a permanent magnet alternator, the output is in the form of electrical energy and the input is mechanical energy. So we basically needed to measure these two results, the input and the output to calculate the efficiency. Since the output is electrical, we measure the loaded voltage and current. The input side is mechanical energy which is generally provided by a motor. The factors to be considered here are speed and torque. All these quantities help us calculate the efficiency of the machine.

Results

The alternator tested was rated at 750rpm. We required the efficiency not only at the rated speed but also at half speed and the customer's cut-in speed. At the rated rpm, the PMGL alternator achieved 95% efficiency. At 400 rpm it was over 90% efficient and at 200rpm, it was 74%.

  The efficiency of more than 90% at less than the rated speed is worth noting. All alternator models at PM Generators Ltd. give very high efficiencies between 85% and 95%. 

Materials for Wind Permanent Magnet Generator

 Winding Wires

In electric industries, winding wires play a very important role. Their role spreads from generators to transformers, control devices and even pumps. Many materials can be used to make wires. The most popular material used is copper. It is the most accepted material. 

Copper has many advantages which makes it a number one choice. It offers very little resistance. It can be either solid or stranded. Materials which make the water impervious to water, grease, chemicals and oil are needed at this stage. Hence insulation used is of tough grade polymer compounds.

Winding wires are either enameled or coated with various types of varnish and other insulating materials. These wires are used as semi finished material for generating electromagnetic fields and transforming electrical energy.

Varnishing of Winding Wires
A layer of insulation is provided on the wires by varnishing. One important feature of these varnishes is that they must resist high temperatures. Wires are mainly made of conductive material; copper is the most popular as said earlier. Varnishes are made of copolymer which is made from thermoplastic of thermosetting resin. The conductor can be covered with one or more layer of varnishing. These layers can withstand temperatures up to 200°C. The resin is made of any of the followings materials like

Importance and need of Varnishing
Varnishing is done to give extra strength and stability to the copper winding wires. Varnishing increases the ability of these wires to withstand partial discharge and voltage peaks at high temperatures. Thus these varnished insulated windings are used to make coils for permanent magnet alternators.

Bearings

To get the correct efficiency we have to make sure all the necessary measures are taken, like using the correct type of bearings. Sealed ball bearings are commonly used , which should be correct in size and should be able to withstand axial loads.

Sealed Ball Bearings

This type of bearing covers the balls and provides a greater degree of protection because the shield on the sealed ball bearing actually comes into contact with the inner race. But this comes with a price; the high contact pressure of the seal against the rotating inner race increases the    friction and torque losses and can cause a buildup of heat as well.

Magnets

Grade: The grade of a magnet refers to the maximum energy product of the material that composes the magnet. In simple terms it is to tell how strong the magnet is. The higher the grade the stronger the magnet. Unit of energy product is Gauss. Sintered Nd-Fe-B will remain indefinitely; they experience a minute reduction in flux density over time. As long as their physical properties remain intact, they can work well with same efficiency for 100 years.

Magnets will start losing their properties if we heat them above their rate temperatures which is why you cannot overload a permanent magnet generator.

We coat the surfaces of the magnets to protect them from external environment and this will not affect the magnetic properties of the magnets. This increases the air gap between the magnets and the device it is held to. The coatings are very thin and hence the air gap change is negligent.

Precision manufacturing

Bearing Housing: These are very important for safe operation and durability of industrial bearings. These are used to mount the bearings safely.

There are many types of bearing housings available. The possibility of relubrication should be kept in mind while choosing the type. Housings which require relubrication are called relube type others are called maintenance free bearing housing. One other type can be split type and unsplit type.