Block and Tackle Series Volume 4 – What Does TENV (Totally Enclosed Non-Ventilated) Mean?
Question:
What does TENV, or Totally Enclosed Non-Ventilated mean in regard to a servo motor?
Answer:
Well – the answer is simply the motor is Totally Enclosed, and Non-Ventilated
Based on NEMA (National Electrical Manufacturers Association) definition, TENV states that the motor housing is fully enclosed and is not ventilated with a fan. The motor is being cooled unassisted (natural convection cooling). Basically, the motor cools by releasing heat into the air and/or conducted through the mounting surface. Again, there are no fans nor are liquid cooling techniques used. TENV motors are not considered airtight, therefore you would not use them in wet environments, but you could use them in slightly damp and definitely dirty environments. They are not suitable for hazardous or explosive environments.
Electric motors generate heat and their continuous performance ratings are determined by the heat they can dissipate. Which is why you see motors that utilize fan cooling to help disperse the heat from the motor windings. Many industrial environments are not suitable for fans since they may get clogged - reducing their ability to cool the motor. Fans can also move dirt and spread it around the machine or environment that might not make for a pleasant working condition or could damage product or processes. Liquid cooling often involves using liquid already on the machine to assist in cooling by running pipes around the motors housing, which increases expense. When a customer is asking for a TENV motor, they are saying “I need an enclosed motor and I can’t have a fan and I don’t want to cool with liquid.” So it’s basically shorthand, but with an official definition.
If you’re like me, you probably asked yourself why you can’t just use a separate fan if you’re not in one of those dusty, dirty situations. Well, when you use an external fan it becomes a TEBC: Totally Enclosed Blower Cooled. BC? Why not FC, Fan Cooled would make more sense right? Well, it’s taken, TEFC is for Totally Enclosed Fan Cooled in other words, a motor with an external fan that is part of the motor (meaning the fan turns when the motor is turning).
Servo motors are often TENV motors. When sizing an application, engineers will consider temperature ratings under different conditions as part of their decision for choosing which motor they’ll use. That’s why environmental information is important when gathering application information. If you’re not going to do anything special to cool the motor, you’d want to make sure the motor doesn’t overheat. Temperature information for a motor should be provided up front by any supplier, but always ask for it if you don’t see it.
On a slightly different but related topic - another rating you may be interested in would be the Ingress Protection or IP Rating - More information can be found on our blog post entitled “4 Tips for Considering Your Servo Motors IP Rating in Your Application”, by Gene Matthews.