Executive Summary

With the increasing number of ASICs being designed for 3-phase voltage input, future Bitcoin mine designs should consider the implementation of a fully uniform 480v 3- phase system. By utilizing this power design miners can become even more energy efficient. Furthermore, this type of voltage rating is abundant throughout North America and is easily scalable.

By doing so miners can save on upfront investment costs, improve operating margins, worry less about miner maintenance, and ultimately utilize power sources more effectively.

Electrical Engineering Refresher

Before explaining why we recommend 480v 3-phase power, it’s important to understand how we got to this point and why most large-scale industrial & commercial industries utilize 3-phase power. To begin let’s discuss the differences between single phase and 3-phase power.

• Single-Phase AC Power

Often referred to as ‘residential’ power, single-phase relies on a three-wire delivery system; one hot wire, one neutral wire, and one ground. With alternating current, commonly referred to as AC, current is constantly reversing in direction of flow. A full power cycle happens in a 360-degree phase change, and the voltage flow reverses itself 50-60 times per cycle, or Hz, depending on the system and country.

We can imagine the two carrying wires as a sine wave always 180-degrees apart with defined frequency and amplitude.

As per figure 1, single-phase voltage hits the origin twice at the same time – no power is delivered to the load at these short snapshots. These brief periods of 0 voltage are no issue for residential applications but are significant for high power loads found in industrial or commercial scale operations.

• 3-Phase AC Power

3-phase AC as per the name, provides 3 separate currents for power. Each phase is separated by 1/3 of time it takes to complete a full power cycle, so instead of 180- degrees apart as in single-phase, 3-phase currents are 120-degrees apart. This is the key difference between single and 3-phase power, and what makes 3-phase power so efficient: there exists no point in time in which there is no power delivered to the load, unlike the simultaneous origin strikes seen in single-phase power cycles.

• 3-Phase Power Benefits

Without diving too deep into power and waveform calculations we can see the simplified equations for single and 3-phase cycles to the left. Where Power is in watts, V is voltage in volts, I is current in amperes and PF is the power factor. Power Loss introduces R or Resistance of the line.

Now let’s compare two circuits with the same voltage and amperes, except one is a single- phase and the latter is 3-phase. Ideally assuming power factor is ‘unity,’ or 1, for both circuits yields: P = V x I x 1 for single-phase and P = V x I x 1 x sqrt(3) for 3-phase.

From this simple comparison and inputting any combination for V and I, all else equal, 3-phase systems will always deliver nearly twice the power as single-phase systems. Furthermore, 3-phase allows the transfer of the same amount of power at higher voltages, reducing the current necessary and thus reducing losses, as compared to single-phase. This efficiency in power delivery combined with no “0” voltage instances is extremely useful for industrial scale loads that require large amounts of MWs at a constant rate and which is why most data centers turn to this delivery method.

Bitcoin Mining Data Centers, Today
To recap, 3-phase power allows for constant delivery of large loads. And today most data centers already make use of this form of power somewhere in their power supply chains, this includes industrial scale Bitcoin mines. However, our vision is to make a uniform 480v 3-phase system and to make clear the benefits of doing so it is helpful to review the current state of Bitcoin mining farms.

• Typical Power Step Down

Before power can be delivered at the rack/ASIC level it must be transformed through several steps to reach the rating that will satisfy power supply units (PSUs) of the miners.

For simplicity let’s assume a mine is receiving power from the substation/grid provider at 13.8 kVa configuration. It will most likely be converted/stepped down to a lower voltage rating, 415v 3-phase, via a medium-voltage-transformer (MVT). After this step it will then hit the switchgear before proceeding to the power distribution units (PDUs) to further distribute the power to individual miner PSUs, figure 3 gives a brief overview.

• Inefficiencies & Phase Balancing

Two main problems arise from the typical Bitcoin mine’s power design:

1. Anytime we step down to a lower voltage, electric current (amps) needs to proportionately increase to deliver the same amount of total power - this means losses in the form of waste heat associated with the transformation and the need for thicker gauge wires to transport the higher current. Although necessary due to electric component design limits, this means inefficient use of total power and higher CAPEX

2. Splitting from a 3-ph to a 1-ph requires constant monitoring to ensure the 3-ph power input is properly balanced by the consumption of the three distinct 1-ph paths to the PSUs of three corresponding ASIC miners. If any ASIC has issues and powers down this will cause an imbalance on the PDU and thus wear & tear on components. To visualize why this would cause an imbalance, in figure 4 if Phase A (A in figure 3) powers down it will slow down the whole power cycle on the other two phases - worse performance and/or premature failure.

Why design for 480v 3-phase?
Now that we understand what 3-phase power is, why it’s good for large scale applications, and how it’s being used in the current state of Bitcoin mining we can get to the crux of this post: Future Bitcoin mines should be designed as power efficiently as possible and keeping in a 480v 3-ph configuration will help bridge this gap.

• Efficient Distribution

This graph compares end-to-end efficiency of power distribution for several different voltages and transformations. We can see a 277v/480v 3-ph VAC is the most efficient for end-at loads above 70%. For mega watt (MW) sized Bitcoin facilities that stay on 24/7, these basis point moves in efficiency add up. For example, Bitdeer’s Rockdale site has a capacity of 580+ MWs, a 277v/480v config would yield us almost 6 MWs of power gained back from losses when compared to the next most efficient line.

• Do More With Less

Comparing power delivery for several 3-ph voltage types at varying capacities, 480v will always deliver more. 480v allows users to hit higher wattage but reduce the amps, and physically reduce the size of circuit lines.

For instance if a load required 17.3 kWs of power but is using a 208v 3-ph source than the current needs to be 48 A. Compare that to 20.0 kWs from a 480v source and the current only needs to be 24 A - half the current means less power loss and thinner wire gauges.

• Potential CAPEX Reductions & OPEX Improvements

Tying into the previous subpoint, 480v 3-ph helps minimize infrastructure cost basis. The lower current example previously will require smaller wire sizes as compared to lower voltage/higher amperage combinations. This means:

1. Upfront installation costs on electrical wiring will be less due to use of less conductive metal material

2. Less losses means a more efficient use of total allocated power giving miners a chance to improve their bottom line

• 480v 3-ph is Common

Industrial applications in the US have long used 480v 3-ph as the standard power for running their loads. 480v is also used in the rest of North America (NA) as well as in countries in South America.

It should be noted that almost ~40% of Bitcoin’s total network hash rate comes from US based miners.

The point being: high availability of the necessary systems and components to run a 480v makes it easier for industrial miners to scale operations.

• Solve Phase Balancing Issues

In the future where next generation miners will be designed for smarter power consumption it stands to reason we will see more 3-phase compliant ASICs. As per below we see several models already exist that allow for 3-phase power. While it makes sense to have ASIC PSUs have a range (~380-480v) to keep compliant with other countries outside of NA, an ASIC that can handle 480v input will solve headaches for NA based industrial scale miners.

If the end IT equipment (ASICs) can handle a 3-ph input at these higher voltages miners will not need to worry about ASIC downtime causing unseen wear & tear on other components in the circuit; they will always be in balance from the PDUs.

Closing Thoughts
On top of their primary task of securing Bitcoin’s network, miners are always thinking of ways to improve efficiency. By adopting a 480v design throughout the mining data center, miners stand to gain many advantages as well as solve problems inherent to legacy mine designs.

• Potential Obstacles

Of course it won’t be straightforward to implement a 480v uniform design and there are certain constraints miners need to solve first.

Standard ASIC connectors are configured for 250v max (C13s and C19s), so even if a PDU can accommodate a higher voltage, the end miner’s PSU needs to be designed for these loads.

Using lower voltage ratings may be easier in the immediate term due to availability and existing equipment.

• Looking Ahead: Utilization in HPC

3-phase power is already commonly used in traditional data centers as well as in accelerated compute. However, in order to maximize power efficiency and lower overall PUE, HPC data centers could stand to benefit from designing a 480v uniform data center. It could mean even more costs savings removing unnecessary step down transformers/UPS and further help with phase balancing at the split of a wye connector if IT equipment is rated for these higher voltages:

A lower TCO, better operating efficiencies and more environmentally friendly.

Contributors

Sources

• https://www.automationreadypanels.com/motor-starters-vfds-soft-starts/480v-3-phase-us-industrial-power/
• https://cdn10.servertech.com/assets/documents/documents/45/original/3_Phase_Power_Data_Center_v02.pdf? 1565384155
• https://chainbulletin.com/bitcoin-mining-map/
• https://www.geeksforgeeks.org/difference-between-single-phase-and-three-phase-voltage/
• https://www.geistglobal.com/sites/all/files/site/geist_ep901_-_three-phase_electric_power_distribution_v2.pdf
• https://www.generatorsource.com/Voltages_and_Hz_by_Country.aspx
• https://pssdistributors.com.au/what-is-the-difference-between-iec-plugs-c13-c14-c19-c20/
• https://www.raptorpowersystems.com/resources/crypto-mining-with-480v
• https://www.techtarget.com/searchdatacenter/tip/Take-data-center-efficiency-to-the-max-on-three-phase- power
• https://www.vertiv.com/en-asia/about/news-and-insights/articles/educational-articles/three-phase-power-what- it-is-and-the-benefits-it-brings/
• https://www.vitalsine.ca/wp-content/uploads/2017/11/Efficiency-Gains-with-480-277V-Power-at-the-Cabinet- Level_STI_Format.pdf