TIDA-00915: TIDA-00915

Dear Sam,

the TIDA-00915 board is a DC/AC inverter and requires DC-input voltage of typically 320VDC. The DC input voltage range is 200V to 450V, please see TIDA-00915 design guide table 2, I've copied the specification below.  

If you have an AC source, I assume a 230V AC single phase, you will need a bridge rectifier and DC-link capacitors to create a DC voltage with minimum DC-voltage ripple.

Regards, Martin

Dear Sam,

thank you for the clarification. So you'd plan TIDA-00915 for energy recuperation, while the motor brakes or to use is as 3-phase AC/DC, so you would swap what we called DC input and AC output with our design. The topology supports 4-quadrant operation, as long as you will stay within the LMG3410 ratings for currents, voltages and temperature it should work. You may want to check the ratings of the DC-link capacitor in that design to ensure it can handle the DC-link current and access voltage during braking - if applicable in your design.

Regards,
Martin

Dear Martin

In relation to our question above; we intend to feed the inverter from its 3-phase AC side and hence we will use it as a rectifier. We have a reason to do that.

 

Based on the rating of the design 00915 (200V, 8Amp) the maximum AC voltage we can feed must have a peak that does not exceed 110V (peak). Correct?

 

Without any filtering at the DC side this will directly (without any control) get a fluctuating DC voltage of ~ 190V at the DC side. That is, +/- 95V DC , which is 110V * cos (30)). Correct?

 

We do not have to use FWD ...with your LMG3410......correct?

I am asking that last question because usually in circuit drawings of power switches they draw the anti-parallel FWD, while in the circuit drawings of the LMG that FWD is never there.

 

Regards

Sam

 

Hi Sam,

Based on the Table 2 in the Design Guide of TIDA-00915, 3-phase voltage of up to 220VAC RMS can be provided as input if you are using as rectifier. 

As for the FWD, LMG3410 can operate in third quadrant with 0V gate drive signal and hence does not need an external FWD. However, VSD drop can be as high as 5-7.8V depending on drain current when gate drive voltage is 0V in third quadrant operation(please refer Section 6.5 of LMG3410 datasheet) - so the dead time should be minimal to reduce third quadrant losses.

Regards

Siva

Dear Siva,

Thank you for the answer.

220 VAC rms phase to neutral, or  380VAC rms phase-to-phase ….Correct?

Regards

Sam

Hi Sam,

I meant 220V AC rms phase to phase. 380VAC rms phase to phase will give a DC voltage of 537V which is higher than the maximum DC link voltage in Table 2 of design guide. DC link voltage should not exceed 450V and 3-phase AC input should be within a value that does not produce a DC voltage greater than 450V.

Regards

Siva

Hi Siva
This rectification will be very inefficient use of LMG specially at high load because it is always in the 3rd quadrant. Correct?

Is there any problem in using FWD (anti-parallel diode) to reduce the voltage drop across the LMG during the 3rd quadrant operation?

Regards
Sam

Dear Siva & Martin,

In using LMG3410-R070 can we use Anti-Parallel Diode (FWD) to reduce losses in the 3^rd quadrant? If this is correct do you have recommendation or part number for this FWD that we ideally should use with that LMG.

Regards

Sam

Hi Sam, 

Yes, you are correct. 220VAC RMS phase to phase will give ~310VDC.

Thanks

Siva

Hi Sam,

In third quadrant, losses will be same as first quadrant when gate signal is applied - only during dead time(no turn-on gate signal to both the FETs) will the higher loss 3rd quadrant operation take place and hence the dead time needs to be minimized to reduce the 3rd quadrant losses. So there is no need for a FWD. Just an optimal dead time with PWM operation will suffice for rectification, regeneration or inversion as the case maybe.

Thanks
Siva

Hi Sam,

Please refer to previous reply on why FWD is not necessary.

Thanks
Siva