# How to wire a conveyor belt's electrical box (frequency inverter, E-stop, direction control)

**URL:** <https://www.robotexchange.io/t/how-to-wire-a-conveyor-belts-electrical-box-frequency-inverter-e-stop-direction-control/4659>\
**Category:** 💡 How-to\
**Tags:** motor, inverter, conveyor-belt, frequency-converter, conveyor\
**Created:** [September 2, 2026, 12:15am UTC](https://www.robotexchange.io/t/how-to-wire-a-conveyor-belts-electrical-box-frequency-inverter-e-stop-direction-control/4659 "2026-09-02T00:15:28Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![thijs](https://www.robotexchange.io/user_avatar/www.robotexchange.io/thijs/32/4_2.png) [@thijs](https://www.robotexchange.io/u/thijs)\
**Post date:** [September 2, 2026, 12:15am UTC](https://www.robotexchange.io/t/how-to-wire-a-conveyor-belts-electrical-box-frequency-inverter-e-stop-direction-control/4659/1 "2026-09-02T00:15:28Z")

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_Based on contributions by ThomasVrakking._

This describes the electrical wiring inside a typical conveyor belt control box: mains power in, safety switching, the frequency inverter (VFD) that drives the motor, and the E-stop / run / direction control wiring. Use it as a reference when building or troubleshooting a conveyor’s electrical box.

> ⚠ This is a mains-voltage (230 V AC) wiring job. Have the wiring checked by a qualified electrician before switching anything on, and always work with the main switch off.

## What you need

- Conveyor with a three-phase motor and a frequency inverter (this guide was written for a Mitsubishi FR-D720S-025SC-EC; the terminal names are similar on most Mitsubishi FR-D700 series drives)
- Main switch
- Circuit breaker
- Distribution block(s) for phase/neutral and for earth
- Potentiometer (for manual speed control)
- Emergency stop switch
- Run/stop and direction switches
- The inverter’s manual, for your exact terminal layout and parameter settings

## Steps

### 1. Power supply connection

1. Connect the 230 V AC supply (from a wall socket) to a main switch.
2. The main switch splits the incoming power into:
  - Phase (L)
  - Neutral (N)
  - Earth (PE – green/yellow)

### 2. Safety and distribution

1. Connect the output of the main switch to a circuit breaker.
2. From the circuit breaker, wire to a distribution block.
3. From the distribution block:
  - Phase (L) and Neutral (N) go to the input terminals of the frequency inverter (VFD).
  - The earth wire (green/yellow) goes to a separate earth distribution block, then to the earth terminal of the VFD.

> ⚠ Check: the original build used a circuit breaker without an earth-leakage (RCD) function, because the lab’s fixed installation already has upstream RCD protection. If you set this conveyor up outside the lab, you must add earth-leakage protection to the circuit breaker yourself.

### 3. Connecting the frequency inverter (FR-D720S-025SC-EC)

1. Connect the three-phase motor directly to the inverter’s output terminals U, V, W, and connect the motor’s earth to the VFD’s PE terminal.

### 4. Control wiring

1. Potentiometer connection (for manual speed control):

2. Emergency stop switch:

3. Run/stop and direction control (via switches):

## Important notes

- The electrical box may contain extra components (a relay, an electrical socket, a 230→24 V power converter, a Mitsubishi servo amplifier) that are not needed to make the conveyor run — you’re free to use them for your own project, but you can ignore them for basic conveyor operation.
- Use safety rings and screws to attach the motor cap correctly.
- Always verify that the control terminals are configured correctly in the VFD’s parameters (e.g. set the input mode so STF/STR are used for run/direction).
- Follow the manufacturer’s official manual for the exact parameter settings and safety precautions for your inverter model.
- Have all wiring work done or checked by a qualified electrician, and make sure it complies with local electrical codes.

 ![Electrical overview of the conveyor control box](https://www.robotexchange.io/uploads/default/original/2X/4/42ddff7acd7ba0f24375e374ff0aa048a440efcf.jpeg)  
 ![Inside the conveyor control box](https://www.robotexchange.io/uploads/default/original/2X/2/2dd5a5da5d2f0667cee92e67ec84472d1ca82019.jpeg)

## Related

- [How to control a conveyor belt over Modbus-RTU from Python (Mitsubishi FR-D720S inverter)](https://www.robotexchange.io/t/how-to-control-a-conveyor-belt-over-modbus-rtu-from-python-mitsubishi-fr-d720s-inverter/4660) — control this same inverter over Modbus-RTU from Python instead of switches
- [How to calculate motor power, RPM and torque for a conveyor belt](https://www.robotexchange.io/t/how-to-calculate-motor-power-rpm-and-torque-for-a-conveyor-belt/4664) — how to size the motor driving this conveyor

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_Rewritten and consolidated (Sept 2026) from the original student how-to’s: [Using conveyor with big electrical box](https://www.robotexchange.io/t/using-conveyor-with-big-electrical-box/3940)._