---
title: "Motor full load current at 415 V: the chart, and the caveats"
description: "Full load current for standard three-phase motors from 0.75 to 160 kW, with contactor, relay and cable figures — and why the nameplate rarely matches the table."
date: "2026-02-04"
author: "Divakar B"
source: "https://energycalchq.com/blog/motor-full-load-current-chart-415v"
license: "© 2026 Divakar B. Quote with attribution to https://energycalchq.com/blog/motor-full-load-current-chart-415v"
---

Everyone who quotes panels keeps a motor full load current chart somewhere —
taped inside a cupboard door, in a spreadsheet, or in their head for the sizes
they meet most often. It answers the question that starts every motor circuit:
how many amps, so what contactor, what relay, what cable.

Here is the chart for 415 V three-phase motors, followed by the part that
matters more — why the number on the nameplate in front of you is usually
several per cent higher than the number in any chart, and which one to design
to.

## The chart

Calculated from `I = kW × 1000 / (√3 × 415 × pf × η)` with efficiency and power
factor typical of IE3 motors at each rating. Protection figures follow the usual
rules: overload relay set at full load current, cable rated at 1.25 times it.

| kW | HP | Full load current | Contactor (AC-3) | MPCB / MCCB | Cable must carry |
|---|---|---|---|---|---|
| 0.75 | 1 | 1.7 A | 9 A | 2.5 A | 2.1 A |
| 1.5 | 2 | 3.1 A | 9 A | 4 A | 3.9 A |
| 2.2 | 3 | 4.4 A | 9 A | 6.3 A | 5.5 A |
| 3.7 | 5 | 7.1 A | 9 A | 10 A | 8.9 A |
| 5.5 | 7.5 | 10.3 A | 12 A | 16 A | 12.9 A |
| 7.5 | 10 | 13.7 A | 18 A | 16 A | 17.1 A |
| 11 | 15 | 19.6 A | 25 A | 20 A | 24.5 A |
| 15 | 20 | 26.6 A | 32 A | 32 A | 33.3 A |
| 18.5 | 25 | 32.3 A | 38 A | 40 A | 40.4 A |
| 22 | 30 | 38.2 A | 40 A | 40 A | 47.8 A |
| 30 | 40 | 51.7 A | 65 A | 63 A | 64.6 A |
| 37 | 50 | 63.5 A | 65 A | 80 A | 79.4 A |
| 45 | 60 | 76.9 A | 80 A | 80 A | 96.1 A |
| 55 | 75 | 93.6 A | 95 A | 100 A | 117.0 A |
| 75 | 100 | 125.3 A | 150 A | 160 A | 156.6 A |
| 90 | 125 | 149.8 A | 150 A | 160 A | 187.3 A |
| 110 | 150 | 182.3 A | 185 A | 200 A | 227.9 A |
| 132 | 180 | 218.3 A | 225 A | 250 A | 272.9 A |
| 160 | 215 | 264.0 A | 265 A | 320 A | 330.0 A |

For a star–delta starter, the main and delta contactors each carry the winding
current — full load current divided by √3, or 0.58 times the figure above — and
the star contactor about a third. A 30 kW star–delta needs three contactors
around 32 A and 18 A rather than one 65 A.

The [motor starter calculator](/tools/motor-starter) works all of this for any
rating, voltage, power factor and starting method, including the star–delta
split.

## Why the nameplate says something different

Take any motor from the chart and compare it with the plate on the machine. The
plate will usually read 5–10 % higher. Neither is wrong.

![Annotated motor nameplate with notes on the current, power factor, speed and duty fields](/blog/motor-nameplate-annotated.svg "The current on the plate is measured on that design. Everything in a chart is an estimate of what the plate would say.")

A chart has to assume a power factor and an efficiency, because it is generated
from a formula. A nameplate reports what that specific design actually drew on
test. The differences come from real things:

- **Smaller motors are worse on both counts.** A 0.75 kW motor might run at
  0.75 power factor and 82 % efficiency; a 160 kW at 0.88 and 96 %. The gap
  between chart and plate is widest at the bottom of the range.
- **Efficiency class.** An IE2 motor draws more current than an IE3 of the same
  output. Charts written before IE3 became mandatory read high; charts written
  for IE4 read low.
- **Pole count.** A 6-pole or 8-pole motor of the same kW has a poorer power
  factor than a 4-pole, and draws more current. Most charts, including this one,
  assume 4-pole.
- **Design voltage.** A motor wound for 400 V and run on 415 V draws slightly
  less current than the chart suggests, and vice versa.

**Where they disagree, use the nameplate.** It describes the motor you bought.
Use the chart for quotations, for sizing before the motor is selected, and as a
sanity check when a nameplate looks wrong — a plate reading 20 % away from the
chart usually means a different pole count, a different voltage, or a plate from
a different machine.

## Full load current is not the only current

Three currents matter on a motor circuit and they are far apart:

| Current | Roughly | Sets |
|---|---|---|
| Full load | 1× | Overload relay, cable size, contactor |
| Starting (DOL) | 6–7× | Volt drop during start, generator sizing, magnetic trip setting |
| Locked rotor | 6–8× sustained | What the relay must trip on before the winding cooks |

A 15 kW motor at 26.6 A draws around 175 A on a direct-on-line start. That
current is why the breaker on a motor circuit must have a C or D curve — a
B-curve device trips magnetically at three to five times rating and will never
let the motor start — and why the cable to a motor at the end of a long run
should be checked for volt drop at starting current, not only at running
current.

## Reading the rest of the plate

The current is what you came for, but four other fields change the design:

**Duty (S1 to S9).** S1 is continuous, and everything in the chart above assumes
it. A motor that starts twenty times an hour is S4 or S5 duty and needs a
class 20 or class 30 overload relay — a standard class 10 relay will trip on
accumulated starting current even though nothing is wrong.

**Service factor.** If the plate carries one — 1.15 is common on motors built to
NEMA practice — the relay may be set up to 1.15 times full load current. If
there is no service factor marked, set it at 1.0.

**Insulation class.** Class F insulation with a class B temperature rise is the
common specification, and the margin between them is what lets the motor
tolerate a hot day. A motor run at class F rise has no margin left.

**IP rating.** IP55 is standard for industrial duty. Outdoor or washdown
locations need IP65 or IP66, and it applies to the terminal box as much as the
frame — which is where water usually gets in.

## Voltages other than 415 V

The chart assumes 415 V. Current scales inversely with voltage for the same
power, so you can move between the common LT voltages without recalculating
from scratch:

```
I(new) = I(415) × 415 / V(new)
```

| Supply | Multiply the chart by |
|---|---|
| 380 V | 1.09 |
| 400 V | 1.04 |
| 415 V | 1.00 |
| 440 V | 0.94 |
| 690 V | 0.60 |

That last row is the reason large motors move to 690 V where the supply allows
it. A 160 kW motor drops from 264 A to about 159 A, and the cable, the
contactor and the busbar all come down with it.

The scaling holds for the current. It does **not** hold for the motor: a
machine wound for 400 V and run at 415 V draws slightly less current than the
arithmetic suggests, because it is being run marginally above its design
voltage. Use it to move between chart rows, not to justify running a motor on
a supply it was not wound for.

## A rewound motor is not the motor on the chart

Rewinding is normal practice and often the right economic call, but it changes
the numbers this chart is built on. A competent rewind typically costs
0.5–1 % of efficiency; a poor one — wrong wire gauge, overheated core steel
during stripping, changed slot fill — can cost 2–4 %.

Efficiency sits in the denominator of the full load current calculation, so
every point lost raises the current the motor draws for the same shaft output.
A motor rewound twice can be drawing meaningfully more than its plate says
while delivering exactly what it always did.

Two practical consequences. The overload relay setting should be checked
against a measured current after a rewind, not left where it was. And on a
motor that has been rewound more than once, the economics of replacement with
an IE3 machine are usually better than they look, because you are comparing
against a degraded baseline rather than the nameplate.

## Two mistakes this chart will not save you from

**Sizing the cable to the contactor.** The contactor is chosen from a standard
range and is often well above the motor's actual current — a 22 kW motor at
38.2 A gets a 40 A contactor. The cable is sized from 1.25 times the *motor*
current, 47.8 A, not from the contactor rating. Then it is derated for ambient,
grouping and installation method, which on a hot cable tray can push it up two
sizes. Work it through with the [cable sizing calculator](/tools/cable-size).

**Adding nameplate currents to size the incomer.** Motors rarely all run at once
and almost never all at full load. Sizing a board on the sum of every nameplate
gives an incomer and a transformer far larger than the plant will ever draw —
apply a demand factor, or better, measure. The [three-phase current
calculator](/tools/three-phase-current) converts a measured or estimated demand
into current for the supply side.

One caution on the chart itself: the efficiency and power factor behind each row
are typical, not guaranteed. For a design being issued for construction, use the
motor manufacturer's data sheet. For a quotation, this is close enough that the
switchgear you price will be the switchgear you fit.