Enclosure Types and Cooling Methods
There are various types of enclosures associated with DC motors. The following are the more common configurations found in industry. The system of cooling or ventilation is inherent in the enclosure design. In most cases, to allow the motor to develop full torque at less than 50% speed, an additional blower is required for motor cooling.

DPFG (Drip-Proof Fully Guarded)
The drip-proof fully guarded (DPFG) type of enclosure is self-ventilated and has no external means of cooling. In many cases, these types of motors can be modified to accept additional outside air. Most DPFG designs can generate 100% rated torque down to 50% of base speed. Figure 3-8 shows a DPFG motor.

DPBV (Drip-Proof Blower Ventilated)
The drip-proof blower ventilated (DPBV) type of enclosure has an integral blower, which may or may not include a filter. The blower is typically mounted on the commutator end to provide constant cooling airflow. It is not uncommon for blower ventilated motors to deliver 100% rated torque down to 10 or 5% of base speed. Figure 3-9 shows a DPBV motor.

DPSV (Drip-Proof Separately Ventilated)
The drip-proof separately ventilated (DPSV) type of enclosure uses ducted air in the CFM amount required to cool the motor. This type of motor is capable of delivering 100% torque down to 10 or 5% of base speed. In many cases, this type is suitable for use in hazardous or contaminated environments. Figure 3-10 indicates a DPSV motor.

TESV (Totally Enclosed Separately Ventilated)
The totally enclosed separately ventilated (TESV) type of enclosure has air flow ducted into and out of the motor in the CFM amount required for cooling. This type of motor is capable of delivering 100% torque down to 10 or 5% of base speed. In many cases, this type is suitable for use in hazardous or contaminated environments. Figure 3-11 indicates a TESV motor.

TENV (Totally Enclosed Non-Ventilated)
The totally enclosed non-ventilated (TENV) type of enclosure has no external cooling, but uses an internal fan to circulate the air within the motor. This type of motor is capable of delivering 100% torque down to 10 or 5% of base speed. Due to the cooling effects, these types of enclosures are not practical for large horsepower ratings. For a comparison, a 100-HP open drip motor would be the approximate equal size of a 30-HP TENV motor. Figure 3-12 indicates a TENV motor.

TEAO (Totally Enclosed Air Over)
The totally enclosed air over (TEAO) type of enclosure has a blower mounted directly on top of the motor. This allows for constant air flow over the external surface of the motor frame. There is no internal cooling effect taking place, only around the outside of the unit. Motors of this type are capable of delivering 100% torque down to approximately 10% of base speed. Figure 3-13 indicates a TEAO motor.

TEFC (Totally Enclosed Fan Cooled)
The totally enclosed fan cooled (TEFC) type of enclosure has an externally mounted fan on the commutator end shaft. Air flow is a direct result of the

speed of the motor. Because of this fact, this type of enclosure is not suitable for low-speed applications. These types of motors are capable of delivering 100% torque down to 60% of base speed. Figure 3-14 indicates a TEFC motor.

TEUC (Totally Enclosed Unit Cooled)
The totally enclosed unit cooled (TEUC) type of enclosure uses an air-toair heat exchanger and receives its cooling through an external blower. The blower draws air into the heat exchanger through the air inlet. An internal blower circulates the internal cooled air throughout the inside of the motor. The external and internal blowers are in two separate chambers to restrict the mixing of outside and inside air.

These types of motors are able to deliver 100% rated torque down to 3 or 2% of base speed (20:1 constant torque applications). Figure 3-15 indicates a TEUC motor.