Typical dv/dt in VFD's 2

[edison123]

What is the typical dv/dt value in a 415 V, 50 Hz input VFD ? Is there a thumb rule like 10 times input voltage ?

 

[HCBFlash]

Are you asking about the actual turn-on / turn-off time? Where this is a concern, it would be a characteristic of IGBTs, approximately 0.10 micro-sec. System DC buss voltage would be the actual determining factor to calculate the value, which would be several percent higher than input RMS voltage value.In my experience/understanding the dV/dt is a function of buss voltage, switching frequency and total load circuit inductance. Statement of DC buss capacity would also have to be calculated and expressed with a load inductance factor.

In working with a few different VFDs I've used MTE's products. They seem a bit more focused on VFD applications than Hammond. Some MTE info of possible value is at

http://www.mtecorp.com/solving.html

Hammond transformers info says:

FAQ 108.
What is the typical "RC" DV/DT Filter Reactor performance?
The RC series DV/DT filter reactors combine appropriate values of inductance, capacitance and resistance to form a filter, which reduces DV/DT and peak voltages from the PWM voltage waveform. This combined with a 3% impedance reactor that will reduce motor heating harmonics, will significantly increase the life of the motor.
Long lead length motor drive applications can experience motor terminal peak voltage spikes twice the DC bus voltage, and higher. Therefore motor terminal voltage peaks of 1200 volts for 480V drives and 1600 volts for 600V drives are not uncommon. The highest peak voltages will typically occur in lower HP applications.

 

[edison123]

Thanks a lot HCBFlash. Exactly what I was looking for.

 

[ozmosis]

Here's an interesting booklet to read about the subject:

http://www.gambica.org.uk/pdfs/Report1_3rd Edition.pdf

 

[edison123]

Thanks ozmosis. That was a good paper.