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# TIDA-00195 DC BUS CAPACITOR

Other Parts Discussed in Thread: TIDA-00195

Hi,

1. TIDA-00195 is supplied from dc source. I want to use 3 phase 400VAC via bridge rectifier.

2. Can I use this equation for keeping bus ripple voltage under specific percentage?

Eg.

VbusRipple= I(bus) / 6*f(line)*C(bus) = 10A / 6*50Hz*,0011F ≈ %5 Ripple for 600V Bus voltage.

3. Is %5 (max)  ripple bus voltage reasonable for reliable induction motor application?

4. How can I calculate the DC BUS capacitor RMS ripple current? Could you suggest an equation by taking account switching frequency, bus ripple voltage and bus current?

5. Is it Using Aluminum Electrolytic and Film capacitor together (paralleled) for high RMS ripple current demanding application reasonable?

Eg. 1000uf aluminum electrolytic bus capacitor is sufficient for keep below the required max bus ripple voltage. But Rms ripple current is below the calculated. So can I use

low capacitance, high ripple current film capacitor as a complementary?

Best regards,

• Hi Ali,

Thanks for reaching to us on these questions.

Seems your design is a 400V*1.732*10A = 6928W inverter ACIM motor drive.

Generally 5% max bus-voltage ripple is OK for an induction motor's reliable running; but it may decide by the specific system requirement and motor characterics, etc.

On the DC BUS capacitor RMS ripple current's accurate assumption, suggest you to use a simulation tool to evaluate it. Both TINA (www.ti.com/.../TINA-TI and PSpice for TI (www.ti.com/.../PSPICE-FOR-TI are OK for it.

Using Aluminum Electrolytic and Film capacitor together (paralleled) in an application is reasonable and widely adopted.

Film capacitors' capacitance is too small and cannot take much share of the ripple current. Add more aluminum electrolytic capacitors or change to higher ripple component for it.

Best regards,

Jerome Shan