Block and Tackle Series Volume 4 – What Does TENV
(Totally Enclosed Non-Ventilated) Mean?
What does TENV, or Totally
Enclosed Non-Ventilated mean in regard to a servo motor?
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
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).
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
Tips for Considering Your Servo Motors IP Rating in Your Application”,
by Gene Matthews.