Question "63 amperes is how many kilowatts at 380 volts" relevant for owners of car garages, workshops and even home electrical networks that use three-phase power. Errors in calculations here are fraught not only with turning off the machines, but also wiring fire or the failure of expensive equipment - from welding machines to charging stations for electric vehicles.

Many car enthusiasts and craftsmen are faced with confusion: why, with the same current (for example, 63A), the power in kilowatts is different for single-phase (220V) and three-phase (380V) networks? The point is power factor (cos ฯ†), features of load connection (star/delta) and even in type of consumer (active or reactive). Let's figure out how to correctly calculate the power for your case - with formulas, examples and warnings about common errors.

If you are connecting in a garage three phase compressor, welding inverter or charger for Tesla, knowing the exact power will help you choose the right cable and machine. And for workshops with several machines the question is "Is 63A enough for 380V?" can become critical - after all, excess load leads to accidents and fines from energy supervision.

In this article:

  • ๐Ÿ”Œ Calculation formulas for a three-phase network (taking into account cos ฯ†).
  • ๐Ÿ“Š Ready tables power for machines 16A, 25A, 32A, 63A.
  • โšก Examples for automotive equipment: welders, compressors, charging stations.
  • โš ๏ธ Dangerous mistakes, which are allowed when connecting 380V in the garage.

Why 63A at 380V โ‰  63A at 220V: difference in power

The main difference between a three-phase network (380V) and a single-phase network (220V) is load distribution method. In a single-phase network, power is calculated using a simple formula: P = U ร— I ร— cos ฯ†, where:

  • P โ€” power in watts (W),
  • U - voltage (220V),
  • I - current (63A),
  • cos ฯ† โ€” power factor (usually 0.8โ€“1 for active loads).

For a three-phase network, the formula becomes more complicated: P = โˆš3 ร— U ร— I ร— cos ฯ†. Here โˆš3 โ‰ˆ 1.73 is the root of three, and U taken line voltage (380V), not phase (220V). That is why, at the same current (63A), the power in kilowatts will be 3 times higherthan in a single-phase network.

For example:

  • ๐Ÿ”Œ 220V, 63A: 220 ร— 63 ร— 0.8 โ‰ˆ 11 kW (if cos ฯ† = 0.8).
  • โšก 380V, 63A: 1.73 ร— 380 ร— 63 ร— 0.8 โ‰ˆ 33 kW.

This means that a three-phase 63A circuit breaker can withstand 3 times more powerthan single-phase with the same rating. But there are nuances!

๐Ÿ“Š What equipment do you connect to 380V in the garage?
Welding machine
Compressor
Electric vehicle charging station
Lathe
Other

Power calculation formula for 380V: step-by-step instructions

To independently calculate how many kilowatts a 63A machine at 380V can withstand, follow the algorithm:

  1. Determine the type of load:
    • ๐Ÿ”ฅ Active (lamps, heating elements, heaters): cos ฯ† โ‰ˆ 1.
    • โšก Reactive (motors, transformers, welders): cos ฯ† โ‰ˆ 0.7โ€“0.85.
  • Check the connection diagram:
    • โญ Star (phase voltage 220V, linear 380V).
    • โ–ณ Triangle (linear = phase = 380V).
    • Substitute the values into the formula: 
      P (kW) = (โˆš3 ร— U ร— I ร— cos ฯ†) / 1000

    Example for welding machine (cos ฯ† = 0.7, star connection): 

    P = 1.73 ร— 380 ร— 63 ร— 0.7 / 1000 โ‰ˆ 28.5 kW

    For heater (cos ฯ† = 1): 

    P = 1.73 ร— 380 ร— 63 ร— 1 / 1000 โ‰ˆ 41.6 kW

    Determine the cos ฯ† of the equipment|Specify the connection diagram (star/delta)|Check the rating of the machine on the body|Take into account starting currents (for motors)-->

    Power table for 380V machines (cos ฯ† = 0.8)

    For convenience, we provide ready-made power values for standard ratings of three-phase machines. The data is relevant for most car services and garage workshops, where cos ฯ† โ‰ˆ 0.8 (mixed load).

    Machine rating (A) Power at 380V, cos ฯ† = 0.8 (kW) Equipment example
    16 8.8 Small compressor, workshop lighting
    25 13.8 Medium power welding inverter
    32 17.9 Charging station for a hybrid car
    40 22.4 Lathe, powerful vacuum cleaner
    63 35.1 Industrial compressor, group of machines

    Please note: if your equipment has cos ฯ† < 0.8 (for example, cheap welders or old engines), the power will be below calculated For accuracy, use data from the device nameplate.

    ๐Ÿ’ก

    If the equipment nameplate indicates power in kVA (kilovolt-amperes), multiply it by cos ฯ† to get the actual power in kW. For example, 20 kVA ร— 0.8 = 16 kW.

    Typical mistakes when connecting 380V in a garage

    Even experienced auto electricians make mistakes when working with three-phase networks. Here are the most dangerous of them:

    โš ๏ธ Attention! Connection single-phase consumers (for example, 220V heater) to a three-phase network without load balancing leads to phase imbalance and triggering of the machine. Distribute the load evenly!
    • โŒ Ignoring cos ฯ†: many take cos ฯ† = 1 for all devices, but for asynchronous motors (compressors, machine tools) it can be 0.6โ€“0.7. This underestimates the actual power by 20โ€“30%.
    • โŒ Wrong cable selection: for 63A at 380V you need a copper cable with a cross-section not less than 16 mmยฒ (or 25 mmยฒ for aluminum). Using thin wires causes heat and fire.
    • โŒ Triangle connection without testing: Some engines are designed for chainring only. Reconnection leads to burnout of the windings.
    • โŒ Lack of RCD: in garages with a damp environment, a three-phase RCD (100โ€“300 mA) is required to protect against electric shock.

    Case study: a car service owner connected compressor 22 kW through a 63A automatic machine, but did not take into account that the starting current of the motor is 3โ€“5 times higher than the rated current. The result is that the machine operates every time it is started. Solution: install machine with characteristic "D" (for high starting currents) or use soft starter.

    What is "inrush current" and why is it important?

    When starting an asynchronous motor (compressor, machine tool), in the first seconds, the current can exceed the rated current by 5โ€“7 times. For example, a 10 kW motor at the moment of starting โ€œpullsโ€ up to 50โ€“70A. If the machine is not designed for such loads (characteristic "C"), it will trip. For garage equipment, machines with characteristic โ€œDโ€ or special ones are optimal. automatic motors.

    Examples of calculations for automotive equipment

    Let's look at real cases from car repair shops and garages:

    1. Welding machine REZANT-205 (380V, 20 kVA)

    Nameplate data: S = 20 kVA, cos ฯ† = 0.7.

    Calculation:

    • Real power: 20 ร— 0.7 = 14 kW.
    • Current: I = P / (โˆš3 ร— U ร— cos ฯ†) = 14000 / (1.73 ร— 380 ร— 0.7) โ‰ˆ 30A.
    • Conclusion: a 32A automatic machine is suitable, 63A is suitable with a large margin.

    2. Compressor Fubag VC/400/50 (3 kW, 380V)

    Data: P = 3 kW, cos ฯ† = 0.8, star connection.

    Calculation:

    • Current: I = 3000 / (1.73 ร— 380 ร— 0.8) โ‰ˆ 5.7A.
    • But! The starting current can reach 20โ€“25A. Therefore, an automatic machine is needed for 16A (characteristic "C" or "D").

    3. Charging station Tesla Wall Connector (22 kW, 380V)

    Data: P = 22 kW, cos ฯ† = 0.95.

    Calculation:

    • Current: I = 22000 / (1.73 ร— 380 ร— 0.95) โ‰ˆ 35A.
    • Conclusion: 40A automatic machine (with a margin of 20โ€“25%).
    ๐Ÿ’ก

    For equipment with high starting currents (compressors, pumps), choose machines with characteristic โ€œDโ€ or use soft starters.

    How to choose a machine and cable for 63A to 380V

    If you determine that your load requires a 63A breaker, follow these rules:

    • ๐Ÿ”Œ Automatic:
      • For active load (heating, lighting): characteristics C63.
      • For engines (compressors, machines): characteristics D63 or automatic motor.
      • Brands: ABB, Schneider Electric, Legrand (avoid no-name!).
    • โšก Cable:
      • Copper: section 16โ€“25 mmยฒ (for example, VVGng 5ร—16).
      • Aluminum: section 25โ€“35 mmยฒ (but not recommended for garages!).
      • Brands: VVGng, NYM (for wet rooms - with marking LS).
    • ๐Ÿ›ก๏ธ Protection:
      • RCD: 100โ€“300 mA (for fire protection).
      • Voltage relay: mandatory for garages with an unstable network (turns off equipment during surges > 260V).
    โš ๏ธ Attention! Often used in garages and workshops simplified grounding diagram (for example, "zeroing"). It's dangerous! For a three-phase network, be sure to organize complete ground loop with a resistance of no more than 4 ohms.

    Example configuration for a car service with a load of 30 kW:

    • Automatic: ABB S203 D63.
    • Cable: VVGng 5ร—25 (5 cores: 3 phases + neutral + ground).
    • RCD: Schneider Electric 4P 100mA.
    • Voltage relay: UBK-380.

    Frequently asked questions (FAQ)

    โ“ Is it possible to connect a 63A 380V circuit breaker to a single-phase load?

    Technically possible, but ineffective. A three-phase 63A circuit breaker, when one phase is connected, will withstand a current of up to 63A, but the power will be limited 14 kW (220V ร— 63A). However, the other two phases will remain unused. It is better to install a separate single-phase machine.

    โ“ Why, when calculated using the formula, it turns out to be 41.6 kW, and in the table - 35.1 kW?

    The table shows the values for cos ฯ† = 0.8, which is typical for a mixed load (motors + lighting). If your equipment has cos ฯ† = 1 (purely resistive load), the power will indeed be higher - up to 41.6 kW. Always check cos ฯ† on the device nameplate!

    โ“ Which machine should be placed at the entrance to the garage if there are several machines inside?

    Calculate total power for all consumers, taking into account cos ฯ†, add 20โ€“30% of the reserve. For example, if the total power is 25 kW, choose an automatic 40โ€“50A. For an accurate calculation, use the formula: 

    I (A) = (P ร— 1000) / (โˆš3 ร— 380 ร— cos ฯ†)
    โ“ Is it possible to use a 63A machine to connect a Tesla charger?

    Yes, but with reservations. Charging stations Tesla Wall Connector (up to 22 kW) require current up to 35A, so 63A is a reserve. However:

    • Use characteristic "C" (and not โ€œDโ€), since the starting currents of the chargers are minimal.
    • Install RCD type "A" (to protect against DC leakage current).
    • Cable - copper 10โ€“16 mmยฒ (even if 6 mmยฒ is suitable for current, the reserve is needed for future upgrades).
    โ“ What happens if you exceed the power on a 63A machine?

    The consequences depend on the degree of excess:

    • 10โ€“20%: The machine may not work immediately, but will heat up, shortening its service life.
    • 30โ€“50%: Thermal release operates after 10โ€“60 minutes.
    • >50%: Instantaneous tripping by electromagnetic release.
    • >100%: contact melting, risk of fire.

    Example: if a 50 kW load is connected to a 63A circuit breaker (at cos ฯ† = 0.8), the current will be ~80A. The machine will turn off in a few minutes, but during this time the cable may overheat.