AC Coupling capacitor

Hi,

Working on a motor drive, I need to supply a sensor with 10vpp 2500Hz. The current shall be in a 50 to 100 mApp order.
The sensor is mainly a transformer, so I want to suppress any DC voltage on supply, in order to never saturate the transformer.
I though about addind two AC coupling capacitor to suppress DC offset, but how to chose their charactérisitic ?

For C choose, I use impedance of the capacitor at the frequency for the Maximum current, and chose the voltage drop acceptable. in my case, it vould be 50mV by capacitor, so C should be C=100mA/(2500*2*PI*50mV)=127µF. Am I Wrong :?:

But for the voltage tolerance of the capacitor, how do I choose It :?:

Regards,

Ze_DIB

ze_dib,
Your capacitance calculation is correct. As far as the voltage rating is concerned, you need to consider the worst case when the circuit is first turned on. Depending on the motor characteristics, it is possible that the initial voltage across the capacitor could approach the 10V peak of the supply, even though the steady state peak voltage would be on the order of 50 X 1.414 = 70.7 mV mV. I would use a capacitor with a 10 V rating minimum.
Regards,
Kral

Added after 4 minutes:

ze_dib
A postscript to my previous reply: You mentioned using 2 capacitors. I'm assuming that you want to use electrolytic capacitors connected back to back to prevent damage due to reverse polarity. Otherwise, you can used metallized film capacitors in parallel to get the required capacitance.
Regards,
Kral

Kral,

thank for a so quick answer.

I mentioned two capacitors because I was thinking to put one capacitor on each entry of the sensor supply.

I wonder if this is very useful : one capacitor shall be sufficient for the AC coupling.
The sine signal is made from two B class amplifier. Those amplifiers are powered by a symetrical 15V supply.

For a failure of one class, B, I should take a capacitor with a 30V rating, don't you think ?

Regards,

Ze_DIB