Electrical Insulation Method: Not All Motors Are Equal
Not all motors are created equal. Even if at first glance the basic specs such as HP, RPM, Frame Size and Phase seem equivalent, swapping one motor brand out for another may cause slight—or sometimes huge—performance issues. This is especially true when a motor application or environment is particularly difficult and/or subjected to sometimes extreme conditions.
Every electric motor manufacturer is going to state that they provide a good, quality manufactured product, and that’s why it’s important for motor users such as OEMs and maintenance professionals to understand what and how certain specs and features increase performance capabilities within their specific application, promote longevity and otherwise benefit them. One important—yet overlooked—feature to a motor is the method of insulation.
Typically the first and main cause of electrical failure in a motor is the breakdown of the insulation used for the coils and windings. That's why it is important to understand how the different types of insulation may affect your motor operation.
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Posted on: March 24, 2015
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Elektrim Performance Series motors with vacuum pressure impregnation (VPI) as standard:
Vacuum Pressure Impregnation, or VPI, is a far more efficient and effective insulation process than conventional varnish “dip and bake” methods utilized by most electric motor manufacturers, which can leave voids and air pockets. Instead, VPI creates a 100% solid mass that offers the best heat dissipation, in addition to completely sealing the windings against moisture and wire to wire vibration, increasing mechanical strength, improving corona protection, promoting longer life, reliability and quieter operation.
Why does it matter?
Solvent varnishes lose up to 70% of its volume during the baking process, which creates a weak structure pitted with trapped air. Air is a very poor conductor of heat, as opposed to a solid mass. Also, multiple varnish dips can create a “heat jacket” around the winding, further reducing heat dissipation. Unlike traditional “dip and bake” methods, VPI provides a 100% solid mass structure that dissipates heat more effectively, and is virtually impervious to oil, moisture and mechanical contaminants.
VPI strengthens the insulation system and extends the service life of a motor, and is the most effective way known to eliminate the dead air spaces that cause hot spots within the motor coils. These hot spots can be 20º higher than the average coil temperature. The VPI process, along with good resin, provides a low thermal resistance path that lowers the average operating temperature of the motor.
During the VPI process, all air and moisture is removed from the windings, and the resin is pressure applied into the windings. This process bonds all the components of the insulation system together to form a solid sealed mass – a far superior conductor of heat. This is also very effective in reducing mechanical vibrations and greatly reduces the audible noise level of the motor.
In addition, the VPI process and resin improves the dielectric capability between windings and between the windings and ground to 5300 volts per dielectric strength and a 220% C temperature rating. This allows the motor to survive higher voltage stress levels without failure. The resulting winding provides many advantages to motor users including greater mechanical strength, reduced vibration and friction of the windings, the highest level of environmental protection and improved heat dissipation by providing maximum penetration of resin throughout the turns of individual coils.
In the end, VPI vastly improves the performance and reliability of all motors, especially those operating in harsh environments or critical applications, and provides a positive return on your investment with long-term electric motor operation. So, the next time you order a motor, check to see if the insulation is VPI applied.
Did you know that for every 10 degrees a motor runs over its rated temperature, the life of that motor's insulation will be cut in half?
Vacuum Pressure Impregnation both protects and keeps your motor running cool.