How many kilowatts can a 63A machine withstand: power calculation for 220V and 380V

Circuit breaker on 63 amps - one of the most popular solutions for protecting electrical circuits in garages, workshops and home panels. But how do you understand how much power in kilowatts it can withstand? The answer depends on the type of network (single-phase or three-phase), voltage and even the ambient temperature.

Many car owners and amateur electricians mistakenly believe that 63A automatic is a universal solution for any load. However, exceeding the permissible power leads to false alarms, overheating of contacts, or, worse, a fire. In this article we will figure out how to correctly calculate the load, avoid errors when choosing and connecting, and also provide ready-made tables for quickly determining the permissible power.

Let us immediately note: the rated current of the machine (63A) is not equal to the maximum load power. Power depends on the network voltage, power factor (cos φ) and even on the duration of the load. For example, in a single-phase network 220V a 63A automatic machine can theoretically withstand up to 13.86 kW, but in practice this figure may be lower due to inrush currents or non-ideal operating conditions.

If you connect powerful equipment - a welding machine, a compressor, an electric boiler or a battery charger - it is important to consider not only the rated power, but also peak loads. For example, when starting an asynchronous motor, the current can exceed the rated current by 5–7 times! In such cases, either an automatic machine with the characteristic is required D (not C), or the use of additional soft starters.

Formula for calculating power for a 63A machine

To determine how many kilowatts a 63-amp machine can withstand, we use Ohm’s law and the power formula: P = U × I × cos φ, where:

• 🔌 P — power in watts (W);
• 🔋 U — mains voltage (220V for single-phase, 380V for three-phase);
• ⚡ I — current in amperes (63A for our machine);
• 📊 cos φ — power factor (for household appliances usually 0.9–1, for engines 0.7–0.85).

For simplified calculations cos φ often taken as equal 1 (ideal case). Then the formula simplifies to: P = U × I.

Example for a single-phase network 220V: P = 220 × 63 × 1 = 13,860 W or 13.86 kW.

But this theoretical maximum without taking into account inrush currents and load duration. Actual permissible power may be 10–20% lower.

For three-phase network 380V the calculation is different: the formula for three-phase power is used: P = √3 × U × I × cos φ, where √3 ≈ 1.73.

When cos φ = 1:

P = 1.73 × 380 × 63 × 1 ≈ 41,580 W or 41.58 kW.

Power table for 63A machine: 220V vs 380V

Below is a table with calculated power values for a 63A machine for different network types and power factors. This data will help you quickly determine whether your equipment is suitable for this machine.

Network type	Voltage, V	cos φ = 1	cos φ = 0.9	cos φ = 0.8	cos φ = 0.7
Single phase	220	13.86 kW	12.47 kW	11.09 kW	9.70 kW
Three-phase	380	41.58 kW	37.42 kW	33.26 kW	29.11 kW
Three-phase (line voltage)	220	23.94 kW	21.55 kW	19.15 kW	16.76 kW

Please note: the table shows long-term permissible loads. During short-term peak loads (for example, starting an engine), the machine may not turn off, but this does not mean that such operation is safe. To protect against inrush currents, use circuit breakers with the characteristic D or K.

If your equipment has cos φ below 0.7 (for example, old transformers or some types of welding machines), the power must be reduced even further or power factor correctors must be used.

Mistakes when choosing a 63A machine: what not to do

Many car owners and self-taught electricians make critical mistakes when choosing and installing a 63A circuit breaker. Here are the most common of them:

• ❌ Ignoring network type. 63A automatic circuit breaker for single-phase network 220V and three-phase 380V - these are two different cases! Connecting a three-phase load to a single-phase circuit breaker will lead to its instantaneous operation or fire.
• ❌ Ignoring starting currents. If you connect a compressor, welding machine or electric motor, their starting current can be 5-7 times higher than the rated current. Automatic machine with characteristics C (the most common) is not intended for such loads - you need D or K.
• ❌ End-to-end connection. If the total power of the equipment is equal to the maximum for the machine (for example, 13.86 kW for 220V), this is dangerous. The machine must have a current reserve of at least 20–30%.
• ❌ Using cheap counterfeits. Slot machines of unknown brands (for example, IEK or EKF economy series) often have underestimated characteristics. For critical circuits, choose ABB, Schneider Electric or Legrand.

⚠️ Attention: If a 63A machine constantly heats up or turns off for no apparent reason, this is a sign insufficient cable cross-section, not machine malfunction. Check that the wire matches the load - for 63A the minimum copper cross-section should be 10–16 mm² (depending on line length).

Another common mistake is installing a machine higher denominationthan the wire cross-section allows. For example, if to a line with a wire 4 mm² (maximum 32A) set the machine to 63A, the cable will overheat, but the machine will not work. This is a direct road to fire!

The total power of the equipment does not exceed 80% of the maximum for the machine |

Cable cross-section corresponds to 63A current (minimum 10mm² for copper)|

Type of machine (C, D, K) suitable for the nature of the load |

Availability of RCD or difavtomat for protection against current leakage |

Correct phasing in a three-phase network (no phase imbalance) -->

Automatic 63A for a garage or workshop: real load examples

Let's look at what equipment can be safely connected to a 63A machine in the normal conditions of a garage or auto repair shop.

Single-phase network 220V (maximum ~12 kW with reserve):

• 🔧 Welding machine Resanta SAI-220 (power 7.5 kW) + lighting (0.5 kW) + charger (1 kW) = 9 kW (stock 30%).
• 🚗 Electric lift (3 kW) + compressor (2.2 kW) + tools (2 kW) = 7.2 kW.
• 🔥 Electric boiler (9 kW) + circulation pump (0.5 kW) = 9.5 kW (risky, better 25A automatic).

Three-phase network 380V (maximum ~35 kW with reserve):

• 🔧 Three welding stations of 7.5 kW each = 22.5 kW (stock 36%).
• 🚜 Connection of machines: lathe (5 kW) + milling (4 kW) + sharpener (1.5 kW) = 10.5 kW (you can add more equipment).
• 🔋 Charging station for batteries (3 phases 5 kW each) = 15 kW.

Important: if the workshop uses asynchronous motors (for example, in compressors or machine tools), their starting current can reach 300–500% from nominal. In this case:

• Use a slot machine with characteristics D (for example, ABB S201 D63).
• Install soft starter or frequency converter.
• Check that the cable size can withstand peak loads (63A and inrush currents may require 16–25 mm²).

What happens if you exceed the power on a 63A machine?

If the power is exceeded for a long time (for example, 15 kW on a single-phase 63A circuit breaker), the following will happen:

1. Overheating of contacts machine - after 10–30 minutes the body will become hot and a burning smell will appear.

2. False positives — the machine will turn off at the slightest current surge.

3. Melting of cable insulation - if the wire cross-section is insufficient, it will lead to a short circuit.

4. Fire - in the worst case, overheating can cause the panel or walls to catch fire.

Which machine to choose: 63A with characteristic C, D or K?

The characteristics of the machine determine at what excess current it will operate. For 63A the following options are available:

Characteristics	Response range	What loads is it suitable for?	Model example
B	3–5 × In (189–315A)	For lighting or low current circuits only	Schneider Acti9 iC60B63
C	5–10 × In (315–630A)	Household sockets, heaters, most tools	ABB S201 C63
D	10–20 × In (630–1260A)	Engines, compressors, welding machines	Legrand DX³ 63A D
K	8–14 × In (504–882A)	Inductive loads (transformers, some types of motors)	Hager NKM63K

The best choice for a garage or workshop is:

• 🔌 Single-phase network: C63 for lighting and sockets, D63 for engines.
• ⚡ Three-phase network: D63 or K63 for machines and compressors.

If you connect welding machine, pay attention to it PV (on duration). For example, a device with PV 60% at a current of 200A it actually consumes: 200A × √(60/100) ≈ 155A at its peak. It requires a machine gun with a reserve - D80 or D100, not 63A.

⚠️ Attention: Automata with characteristics B or C not intended to protect engines! Their use will lead to false positives every time the equipment is started.

Cable cross-section for machine 63A: correspondence table

The circuit breaker protects not only the equipment, but also cable. If the wire cross-section is too small, it will overheat even if the machine does not work. Below is the minimum permissible cable cross-section for a 63A machine, depending on the material and installation method.

Core material	Laying method	Minimum cross-section, mm²	Maximum current, A
Copper	Open (in a tray, on the wall)	10	70
Copper	Closed (in a pipe, groove)	16	75
Aluminum	Open	16	60
Aluminum	Closed	25	65

Important:

• For long lines (more than 30 meters) the cross-section needs to be increased by 20–30% due to the voltage drop.
• If the cable is laid in hot room (for example, next to the boiler), its current load is reduced by 10–15%.
• For three-phase networks cross section is indicated on one phase (for example cable 5×16 means 5 cores of 16 mm² each).

Example: to connect a three-phase compressor with a power of 15 kW (cos φ = 0.8) the current will be: I = P / (√3 × U × cos φ) = 15000 / (1.73 × 380 × 0.8) ≈ 28A.

It would seem that a 32A circuit breaker would be enough, but taking into account the starting currents (up to 140A) you need D63 and cable 5×10 mm² (copper, closed gasket).

Frequently asked questions about the 63A machine gun

Is it possible to install a 63A automatic circuit breaker into a house if the allocated power is 15 kW?

No, it's dangerous. The allocated power of 15 kW at a voltage of 220V corresponds to the current: I = 15000 / 220 ≈ 68A. A 63A circuit breaker will constantly shut down at full load. You need to either reduce the power, or agree on an increase in the limit with the energy sales company and set the machine to 80A or 100A.

Why does the 63A circuit breaker heat up if the load is only 10 kW?

There are several reasons:

• Poor contact at the terminals (wires need to be tightened or stripped).
• Low quality machine (fake brand).
• The cable cross-section is smaller than required (for example, 6 mm² instead of 10 mm²).
• Phase imbalance in a three-phase network (one phase is overloaded).

Check the temperature of the terminals with a pyrometer - if it is more than 60°C, urgently look for the cause.

Which machine should I put on a 200A welding machine?

For a welding machine with a maximum current of 200A, you need an automatic machine taking into account PV (on duration). When PV 60% effective current: 200A × √0.6 ≈ 155A. Optimal choice:

• Automatic D160 or D200 (for example, ABB S201 D160).
• Cable 3×50 mm² (copper) or 3×70 mm² (aluminium).

A 63A circuit breaker is absolutely not suitable for such a device!

Is it possible to replace a 63A circuit breaker with an 80A one if the wire holds up?

Technically possible, but illegally, if the allocated power is not increased. Energy sales companies check the rating of the input machine during inspections. If it exceeds the agreed limit, you will be required to replace it back or pay for an increase in capacity. In addition, this is dangerous: in the event of a short circuit, the current can exceed the breaking capacity of the circuit breaker (for example, a 63A circuit breaker usually has a breaking capacity of 4.5–6 kA, and 80A - 6–10 kA).

How to check if the 63A machine is fake?

Signs of a fake:

• Uneven or dull markings (originals ABB, Schneider it is clear and contrasty).
• Plastic smells like chemicals or is easily scratched.
• The weight is less than the original (eg. ABB S201 C63 weighs ~200 g).
• No certificate or marking TR TS.

Buy machines only from authorized dealers or trusted stores (for example, 220pro.ru, ETM).