VFDs temperature raise

Apply the laws of thermodynamics.

https://www.engineeringtoolbox.com/variable-frequency-drives-d_656.html

How efficient is the VFD? What is the ambient temperature? What is the airflow in stones per fortnight?

https://www.engineeringtoolbox.com/air-specific-heat-capacity-d_705.html

Typically, the VFD vendor may provide the thermal impedance of their unit. Or at least give you a range of acceptable temperature and humidity values.

You say "VFD panel". This implies the VFD is inside a larger control enclosure. The VFD manufacturer's literature should give its efficiency under load, as well as some idea of its heat loss when only lightly loaded. Add this to the totals of all other heat sources in the enclosure (such as control transformers, contactor coils, inductor losses, etc.

The control enclosure has to be able to dissipate all this heat in some way, such as radiative cooling into the surrounding air, cold air streams, air conditioning units, cooling fans through filters, etc. If your VFD is designed with cooling fins for mounting through the wall of the enclosure (fins on the outside and all else inside) your heat loss into the enclosure will be much less--but you may need an external fan to push air past the fins and you would need a maintenance plan to keep it clean. Enclosure manufacturers have formulas to tell how much heat they can dissipate for a given ΔT between the inside and outside for a given surface area.

However, the best way is to use the VFD's on temperature sensor and program it to display on the VFD controller, so you know its actual temperature and can respond accordingly.

--JMM

Maybe you are not looking for the temperature rise, but for the heat gain of the equipment so that you can size your cooling equipment?

The temperature rise of the VFD is determined or measured by the VFD manufacturer, using data and conditions not normally published for the end user. The end user usually has no need for this information, except perhaps in unusual explosion risk environments.

The possibility of a flammable gas/air mixture near a <...VFD...> doesn't bear thinking about.

A novice engineer, that doesn't know how to apply thermodynamic laws, designing anything in an explosive atmosphere is a recipe for disaster.

One might pick up the phone and talk to the equipment manufacturer directly and without involving the forum, perhaps.

If you cannot get the heat rejection values from the VFD manufacturer, or you have not selected a supplier yet so you want to be sure, modern VFDs are 96-97% efficient, so worst case you could use 4% of the power as their rejected heat. I have seen some that claim 98% eff., but those are “marketing values” and are of dubious engineering value.

Calculating the temperature rise of wherever / however that VFD is mounted then becomes a standard temperature rise procedure.

Dear Mr. NVR Srinivas,
could you share your mobile number?

I will call you for discussions on various topics posted by you.

Hemant Sawarkar

TMEIC, Mumbai