From Motors and Drives

Over Temperature Conditions
Placing the motor into overload conditions is one cause of over-temperature. High ambient temperatures and dirty or clogged air filters on the machine or motor blowers also contribute to over-temperature failures. High temperature inside the motor cause expansion stress in the wire insulation, resulting in cracks, which in turn can cause contamination and eventual wire failure. The shrinking and hardening of the wire lacquer insulation is a cause for loss of insulation strength.

Ambient Temperature
Typical recommendations are for the motor ambient conditions not to exceed 40oC (104oF). Most motors are designed for continuous operation at this ambient temperature. However, motors that will continuously be used in higher temperatures will typically be designed with a lower temperature rise class of insulation.

DC motor insulation must have mechanical and dielectric strength. It must withstand the normal handling necessary in the assembly of the motor, as well as operation thereafter. The major insulation classes are A, B, F, and H, and a brief description is as follows:

  • Class A is the lowest grade, suitable for typical household appliances, but not normally industrial applications.

  • Class B is general purpose, used in many industrial applications. More demanding...

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Products & Services
DC Motors
DC motors are most commonly used in variable speed and torque applications. They include brushless and gear motors, as well as servomotors.
Stepper Motors (Rotary)
Stepper motors use a magnetic field to move a rotor in small angular steps or fractions of steps. They provide precise positioning and ease of use, especially in low acceleration or static load applications.
AC Servomotors
AC servomotors are responsive, high-acceleration motors typically constructed as permanent magnet synchronous motors.
DC Servomotors
DC servomotors are generally small and powerful for their size, and easy to control. Common types of DC servomotors include brushless or gear motors.

Topics of Interest

Introduction Basically, four different types of DC motors are used in industrial applications: series wound, shunt wound, compound wound, and permanent magnet. Several factors must be considered when...

AC Motor Types Introduction AC motors can be divided into two major categories-asynchronous and synchronous. The induction motor is probably the most common type of asynchronous motor (meaning speed...

Protection and Ratings Motor Protection The typical method of starting a three-phase induction motor is by connecting the motor directly across the power line. Line starting a motor is done with a...

Control of Speed, Torque, and Horsepower Control of Speed The speed of a squirrel cage motor depends on the frequency and the number of poles for which the motor is wound. The higher the frequency,...

IEC Ratings At this point, it would be helpful to briefly review IEC motor ratings and then compare IEC with NEMA. The motor market today has become more global, with IEC rated motors on equipment...