This is a 2-pole stator with the three phases spaced at 120 intervals. Look at the 3-phase motor stator shown in the accompanying diagram. 4: What is a rotating magnetic field, and why does it rotate?Ī rotating magnetic field is one whose north and south poles move inside the stator, just as though a bar magnet, or magnets, were being spun inside the machine. If you need a 12.5-hp motor, buy one service factor should only be used for short-term overload conditions. If the 10-hp motor is operated continuously at 12.5 hp, its insulation life could be decreased by as much as two-thirds of normal. Keep in mind, however, that a 10-hp motor with a 1.25 service factor is not a 12.5-hp motor. Note that when being driven above its rated load in this manner, the motor must be supplied with rated voltage and frequency. For example, if a 10-hp motor has a 1.25 service factor, it will successfully deliver 12.5 hp (10 x 1.25) without exceeding specified temperature rise. Service factor is the load that may be applied to a motor without exceeding allowed ratings. Check out this additional asset from our team:ĮC&M eBook: The Secret to Better Motor Health If excessive brush wear is a problem in such an environment, you may have to humidify the area where the machine is operating. Insufficient current density inhibits the formation of this film and can result in excessive brush wear.Īlso, very low humidity environments do not provide enough moisture for the formation of the lubricating film. This film is composed of moisture, copper, and carbon. Proper current density is required to make certain that a lubricating, conductive film forms on the commutator or slip ring. of brush) must be correct for the application. Remember, current density (amperes per sq in. If wear is still excessive, you should investigate the type and size of brush being used. If the pressure is increased above the optimum amount, the total wear again increases because mechanical friction increases.Īlways make sure that the brush pressure is set to the manufacturer's recommended level. If the pressure is decreased below this amount, the total wear increases because the electrical wear increases.
Mechanical friction increases with brush pressure electrical wear decreases with brush pressure.įor any given brush installation, there is an optimum amount of brush pressure. Electrical wear is caused by the arcing and sparking of the brush as it moves over the commutator. Mechanical friction is caused by the rubbing of the brushes on the commutator or slip ring. Why?īrush wear comes from two basic causes: mechanical friction and electrical wear.
2: I have relieved the spring tension on my brushes, and they still wear too fast. Check out this additional video asset from our team:ĮC&M Tech Talk - Episode 3: Getting Started on Motor Starters Because the armature is always the rotor on DC machines, many electricians and engineers mistakenly believe that the armature is the rotor on all motors and generators. In DC machines, both motors and generators, the armature is the rotor, and the field is the stator. Thus, the armature is the stator and the field is the rotor.ĭC machines. Most large machines, however, have a rotating field and a stationary armature.Ī synchronous motor is virtually identical to a synchronous generator. In small generators, the field windings are often on the stator, and the armature windings are on the rotor. The armature is the winding to which the load is connected.
#WHAT IS A MOTOR WINDING GENERATOR#
The field of a synchronous generator is the winding to which the DC excitation current is applied.
Usually, the terms "armature" and "field" are applied only to alternating current generators, synchronous motors, DC motors, and DC generators.Īlternating current generators. The armature winding is that which generates or has an alternating voltage applied to it. The current in the field does not alternate. The field of a machine is the part that generates the direct magnetic field. Also by definition, the rotor includes all of the rotating electrical parts. 1: Armature, field, rotor, stator: which is which?īy definition, the stator comprises all of the nonrotating electrical parts of a generator or motor. The explanations are brief and practical due to space limitations however, they will enable you to have a better understanding of this equipment. This article will answer seven of the most commonly asked questions. Rotating equipment is so common, yet so misunderstood, that even highly experienced electricians and engineers are often plagued with questions about their operation.