---
title: "Magnetic-impulse-gravity rapper (MIGI)"
description: "A magnetic-impulse-gravity (MIGI) rapper uses an electromagnet to lift a steel plunger and then release it, letting the plunger fall under gravity onto an anvil rod that conducts the impact down into the collecting-electrode frame. It is the dominant rapper design in American-style ESPs from suppliers including B&W, Mitsubishi Heavy Industries, Hamon Research-Cottrell, and Siemens / KC Cottrell legacy designs."
canonical_url: "https://sylio.co/glossary/magnetic-impulse-gravity-rapper"
last_updated: "2026-06-28T02:29:31.183Z"
---

A **magnetic-impulse-gravity (MIGI) rapper** uses an electromagnet to lift a steel plunger and then release it, letting the plunger fall under gravity onto an anvil rod that conducts the impact down into the [collecting-electrode](/glossary/collecting-electrode) frame. It is the dominant rapper design in American-style ESPs from suppliers including B&W, Mitsubishi Heavy Industries, Hamon Research-Cottrell, and Siemens / KC Cottrell legacy designs.

## Operation

A MIGI rapper is normally mounted on the [ESP penthouse](/glossary/esp-penthouse) above the plate stack. Plunger lift, drop height and firing frequency are programmed in the rapper-controller PLC, with each rapper firing in sequence across the field. Compared with [tumbling-hammer designs](/glossary/tumbling-hammer-rapper), the MIGI rapper offers individual plate targeting and easy tuning of impact intensity, but at the cost of greater electrical infrastructure and a more complex top-of-ESP layout.

## Where sonic horns complement MIGI rappers

MIGI rappers excel at the top of the plate but lose impact transmission towards the bottom. [Sonic horns](/glossary/sonic-horn) installed on the penthouse cover the upper plate volume and discharge electrodes; horns mounted at the [hopper](/glossary/esp-hopper) wall cover the bottom region. The combination defends against both [back-corona](/glossary/back-corona) and hopper bridging that MIGI rapping alone leaves vulnerable.

## Related terms

- [ESP rapper](/glossary/esp-rapper)
- [Tumbling-hammer rapper](/glossary/tumbling-hammer-rapper)
- [Electrostatic precipitator](/glossary/electrostatic-precipitator)
- [Sonic horn](/glossary/sonic-horn)