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I was recently researching about this Telsa electric car inverters where i found one intresting thing. Usually in the voltage source inverter the DC bus voltage will be around 600 to 650 V considering 3 phase motor voltage of 400 VAC line voltage.

But these Telsa SRM motor voltage is given as 350 and the battery voltage given to the motor, DC bus voltage which is 400 VDC and they don't have any boost converter on the input side.

I am curious on how they running the motor with 400 VDC.

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  • \$\begingroup\$ Have you got a schematic? Are you looking for a schematic? Might it be not possible to get a schematic due to IP reasons? If someone has a schematic, do you think it's likely they'll post it given its highly likely to be protected in law? \$\endgroup\$
    – Andy aka
    Commented Jul 2, 2020 at 19:28
  • \$\begingroup\$ Not exactly looking for schematic, just curious and I thought that is some obvious thing in the drive design. \$\endgroup\$
    – HEMARAJ J
    Commented Jul 3, 2020 at 10:32
  • \$\begingroup\$ Where are you getting the information that the MOTOR is designed as 350V? The DC bus SYSTEM is designed for that, but the motor itself is custom made for the application, we don't actually know their detailed design criteria as far as I can tell. So it's highly likely that they are designing the motor around a much lower AC motor voltage, probably closer to 230VAC. Since they are 100% in control of what the motor will see from the inverter, i.e. this is not a commercially available motor designed to work with or without an inverter, they don't need to conform to any industry standards. \$\endgroup\$
    – JRaef
    Commented Jul 9, 2020 at 19:46
  • \$\begingroup\$ roperld.com/science/teslamodels.htm \$\endgroup\$
    – HEMARAJ J
    Commented Jul 10, 2020 at 4:29

2 Answers 2

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Most electric vehicles currently use a battery voltage of around 400v directly feeding the drive motors via an inverter. They can be designed for any convenient voltage.

There are advantages to using higher voltages such as reduction of copper weight for wiring harnesses and the current output required from the inverter but until recently the higher voltage semiconductors required were much more expensive. It is a trade-off.

The J1772 standard on which Most EV chargers are based is designed for 300-500V although a newer version of the standard supports up to 1000v and Porsche and Hyundai now have vehicles with 800V battery and motor systems. Interestingly they do have a DC to DC converter to allow charging on 400V chargers.

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The induction motor has fewer turns of heavier wire than normal .The power of the motor is the same .It is just more amps at less volts .Say if you consider higher DC bus voltages like Porshe the induction motor would have more turns of lower diameter wire.If the Bus DC voltage was really high like thousands then insulation issues would kill the concept .If the DC bus volts was really low like say 48 then the motor wire would be very thick and cable copper losses would be high unless you used very heavy copper.Sure you could use a boost converter like you said but at the power ratings needed it would cost some money and add some weight and waste some power.

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  • \$\begingroup\$ Although the motor windings would need to be of heavier wire there would be fewer turns, the motor design is not intrinsically any more efficient at higher voltages. The cable harnesses tend to be more efficient at higher voltages as insulation for 1000v is not much heavier than for 500v and doesn't take up much more space. \$\endgroup\$
    – Kevin White
    Commented Jun 1, 2021 at 0:35

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