DUCTED VACUUM BASICS


VACUUM MOTOR DESIGN AND OPERATION

VACUUM MOTOR DESIGN AND OPERATION

The most common ducted vacuum motor consists of a rotating armature and a stationary field. The armature is made of a laminated iron core which is wound with copper enamel-insulated wire. The windings are attached to a copper commutator near one end of the armature. The commutator has individual bars of copper which are positioned in the shape of a drum. The motor brushes are carbon rods which are held against the commutator in order to carry the electrical current to the windings on the armature. The field consists of a laminated iron frame on which one or two coils of copper wire are wound. It is shaped so that it wraps around the core of the armature on two opposite sides. Since the same current passes through the field coils and the armature coils, it is termed a series motor. As current passes through the coils in the field and armature, magnetic fields are created by each of them. It is the attracting or repelling of these fields which cause the armature to rotate within the field. The fans (impellers) are an integral part of the vacuum motor as the fan housings and the motor are assembled as a complete unit by the manufacturer.

Being a series type motor it is capable of creating high levels of torque for its size. As current increases through the motor, the magnetic fields created by both the armature and field increase proportionally. Therefore, with lighter loads the torque is proportional to the square of the amount of current flowing through the motor. If the current is doubled, the torque is increased by four times. Under heavy loads the field’s magnetic strength reaches a point of saturation whereby it can no longer increase. Then the torque increases only in proportion with the change in the current flow. Vacuum motors are designed to operate at very high speeds under moderate to heavy loads.

The load to a vacuum motor is an interesting and unusual phenomenon. One or more fans (impellers) are attached to the motor shaft and are rotated at a very high speed. The air entering the fans is forced to spin with the fans as it passes through it. The load to the vacuum motor is the force needed to overcome the inertia of the air as it enters the fans. When you reduce the air flow to the motor by increasing air flow resistance, the load on the motor is actually reduced so the motor speed increases and current through the motor decreases. The effect of this is to increase the suction created by the motor which helps to counteract the effect of the resistance to the air flow. If you restrict the air flow completely, it will create its maximum possible suction. This is what happens when a vacuum gauge is used to measure sealed vacuum. In reality, it is greater than the suction which is produced in the normal operating range of the motor.

A substantial amount of energy is dissipated in the form of heat. This is primarily the result of resistance in the copper windings on the armature and field as current flows through them.

BYPASS & FLO THRU MOTORS

Most ducted vacuum cleaners currently use what is known as a bypass motor. In this type of motor, a separate fan circulates clean air around the armature and field to cool them. This design is also used on almost all commercial vacuum cleaners and steam cleaners since it is unsafe to pass damp or wet air over the electrical components. In the event that a ducted vacuum system with a bypass motor is operated without filtration, the dirt and dust will be exhausted without any damage to the motor itself.

Almost all portable and some ducted vacuum cleaners use a flow-thru motor. The air which has already passed through the fans (impellers) is directed around the armature and field to cool them after it exits the fans. This usually makes for quieter operation as there is no separate cooling fan required. Since the motor could overheat if the air flow is greatly or completely restricted, a mechanism should be provided to either stop the motor at a preset temperature or open a safety valve to allow for extra air flow to cool the motor. It is also very important for ducted vacuum systems using flow-thru motors to have very good quality filtration as any particles remaining in the air will have an abrasive effect on the armature and carbon brushes, which will shorten their life. Further more, if a flow-thru motor is operated with no filtration in place considerable damage to the motor is likely.

VACUUM MOTOR DESIGN AND OPERATION

VACUUM MOTOR DESIGN AND OPERATION

The most common ducted vacuum motor consists of a rotating armature and a stationary field. The armature is made of a laminated iron core which is wound with copper enamel-insulated wire. The windings are attached to a copper commutator near one end of the armature. The commutator has individual bars of copper which are positioned in the shape of a drum. The motor brushes are carbon rods which are held against the commutator in order to carry the electrical current to the windings on the armature. The field consists of a laminated iron frame on which one or two coils of copper wire are wound. It is shaped so that it wraps around the core of the armature on two opposite sides. Since the same current passes through the field coils and the armature coils, it is termed a series motor. As current passes through the coils in the field and armature, magnetic fields are created by each of them. It is the attracting or repelling of these fields which cause the armature to rotate within the field. The fans (impellers) are an integral part of the vacuum motor as the fan housings and the motor are assembled as a complete unit by the manufacturer.

Being a series type motor it is capable of creating high levels of torque for its size. As current increases through the motor, the magnetic fields created by both the armature and field increase proportionally. Therefore, with lighter loads the torque is proportional to the square of the amount of current flowing through the motor. If the current is doubled, the torque is increased by four times. Under heavy loads the field’s magnetic strength reaches a point of saturation whereby it can no longer increase. Then the torque increases only in proportion with the change in the current flow. Vacuum motors are designed to operate at very high speeds under moderate to heavy loads.

The load to a vacuum motor is an interesting and unusual phenomenon. One or more fans (impellers) are attached to the motor shaft and are rotated at a very high speed. The air entering the fans is forced to spin with the fans as it passes through it. The load to the vacuum motor is the force needed to overcome the inertia of the air as it enters the fans. When you reduce the air flow to the motor by increasing air flow resistance, the load on the motor is actually reduced so the motor speed increases and current through the motor decreases. The effect of this is to increase the suction created by the motor which helps to counteract the effect of the resistance to the air flow. If you restrict the air flow completely, it will create its maximum possible suction. This is what happens when a vacuum gauge is used to measure sealed vacuum. In reality, it is greater than the suction which is produced in the normal operating range of the motor.

A substantial amount of energy is dissipated in the form of heat. This is primarily the result of resistance in the copper windings on the armature and field as current flows through them.

BYPASS & FLO THRU MOTORS

Most ducted vacuum cleaners currently use what is known as a bypass motor. In this type of motor, a separate fan circulates clean air around the armature and field to cool them. This design is also used on almost all commercial vacuum cleaners and steam cleaners since it is unsafe to pass damp or wet air over the electrical components. In the event that a ducted vacuum system with a bypass motor is operated without filtration, the dirt and dust will be exhausted without any damage to the motor itself.

Almost all portable and some ducted vacuum cleaners use a flow-thru motor. The air which has already passed through the fans (impellers) is directed around the armature and field to cool them after it exits the fans. This usually makes for quieter operation as there is no separate cooling fan required. Since the motor could overheat if the air flow is greatly or completely restricted, a mechanism should be provided to either stop the motor at a preset temperature or open a safety valve to allow for extra air flow to cool the motor. It is also very important for ducted vacuum systems using flow-thru motors to have very good quality filtration as any particles remaining in the air will have an abrasive effect on the armature and carbon brushes, which will shorten their life. Further more, if a flow-thru motor is operated with no filtration in place considerable damage to the motor is likely.