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The Bulk Power Regulator mentioned in the blog post is essentially an 400V DC supply that powers everything else in the rack (including the blowers with threeph

by dfox 7y ago

The Bulk Power Regulator mentioned in the blog post is essentially an 400V DC supply that powers everything else in the rack (including the blowers with threephase motors and their own DC/AC invertor). So it is similar except the power supply is built on modern power electronics and is quite small and internal in the rack.

magduf 7y ago
>The Bulk Power Regulator mentioned in the blog post is essentially an 400V DC supply that powers everything else in the rack (including the blowers with threephase motors and their own DC/AC invertor). Any decent motor these days is a brushless DC motor, so it runs on DC voltage, except that it really doesn't. It gets DC voltage from a power supply (or it rectifies AC voltage to get DC, just like your computer's power supply), and then uses that to drive a motor drive (controller) (a box of electronics that runs the motor). The motor drive generates 3-phase AC power which is actually used to power the windings of the physical motor. The motor includes feedback devices which tell the controller the motor shaft's position so it knows where in the AC cycle the output waveform should be. There's always a lot of confusion about these motors because of this: they're called "brushless DC" (BLDC), but also 3-phase AC, and both are correct. The key is that the controller is really an integral part of the motor. It's similar to how your CPU probably runs on 1.8VDC, but you don't actually supply it that from your computer's power supply, the motherboard has its own voltage regulator to create that. You would never actually make a separate 1.8V power supply for a CPU, because it wouldn't work very well (high losses over distance); it's much more efficient to have the regulator closely coupled to the CPU.
- blattimwind 7y ago
  > Any decent motor these days is a brushless DC motor Most applications are perfectly fine with asynchronous motors which don't require extra power electronics. The increase in efficiency from IE3 asynchronouos to IE4 synchronous/SRM/hybrid is pretty small and costs a bunch.
  - magduf 7y ago
    Depends on what it is. Even the little fans in desktop computers now are BLDC now, with the controller fitting on a tiny PCB inside the hub of the fan. They're simpler versions, though, with hall-effect feedback rather than an encoder. The power electronics these days are dirt cheap.
    - blattimwind 7y ago
      > Even the little fans in desktop computers now are BLDC now Those are at the lower end of the power spectrum of electric motors (which spans approximately 10 orders of magnitude from a few mW to hundreds of MW) and have been BLDCs for a very long time. To see something else in a PC you probably have to go all the way back to the IBM PCs. > The power electronics these days are dirt cheap. For a <1 W fan, yes, but when you want to run a 5.5 kW saw it still costs real money and the motor is more expensive.
- dfox 7y ago
  The reason why I specifically mentioned the blower motors is because the blowers in most mainframes I have seen have use small(-ish) industrial 3phase synchronous motors, not purpose-designed BLDC motors.

by dfox 7y ago

magduf 7y ago

>The Bulk Power Regulator mentioned in the blog post is essentially an 400V DC supply that powers everything else in the rack (including the blowers with threephase motors and their own DC/AC invertor). Any decent motor these days is a brushless DC motor, so it runs on DC voltage, except that it really doesn't. It gets DC voltage from a power supply (or it rectifies AC voltage to get DC, just like your computer's power supply), and then uses that to drive a motor drive (controller) (a box of electronics that runs the motor). The motor drive generates 3-phase AC power which is actually used to power the windings of the physical motor. The motor includes feedback devices which tell the controller the motor shaft's position so it knows where in the AC cycle the output waveform should be. There's always a lot of confusion about these motors because of this: they're called "brushless DC" (BLDC), but also 3-phase AC, and both are correct. The key is that the controller is really an integral part of the motor. It's similar to how your CPU probably runs on 1.8VDC, but you don't actually supply it that from your computer's power supply, the motherboard has its own voltage regulator to create that. You would never actually make a separate 1.8V power supply for a CPU, because it wouldn't work very well (high losses over distance); it's much more efficient to have the regulator closely coupled to the CPU.

blattimwind 7y ago
> Any decent motor these days is a brushless DC motor Most applications are perfectly fine with asynchronous motors which don't require extra power electronics. The increase in efficiency from IE3 asynchronouos to IE4 synchronous/SRM/hybrid is pretty small and costs a bunch.
- magduf 7y ago
  Depends on what it is. Even the little fans in desktop computers now are BLDC now, with the controller fitting on a tiny PCB inside the hub of the fan. They're simpler versions, though, with hall-effect feedback rather than an encoder. The power electronics these days are dirt cheap.
  - blattimwind 7y ago
    > Even the little fans in desktop computers now are BLDC now Those are at the lower end of the power spectrum of electric motors (which spans approximately 10 orders of magnitude from a few mW to hundreds of MW) and have been BLDCs for a very long time. To see something else in a PC you probably have to go all the way back to the IBM PCs. > The power electronics these days are dirt cheap. For a <1 W fan, yes, but when you want to run a 5.5 kW saw it still costs real money and the motor is more expensive.
dfox 7y ago
The reason why I specifically mentioned the blower motors is because the blowers in most mainframes I have seen have use small(-ish) industrial 3phase synchronous motors, not purpose-designed BLDC motors.