Introduction; Description; Key Features; Hardware - KROM 21 Owner's Manual

1 Introduction

With the KROM system from Genmag AB you can measure the magnetic flux density in the airgap of
synchronous generators and motors at full speed. Measurements should be performed at reduced field
current to avoid magnetic saturation of the steel. Stator currents will also affect the measurement.

2 Description

KROM utilises low profile Hall sensors which are glued to a stator tooth of the machine. The signal
from these sensors combined with optical phase measurement enable identification of any defective
pole. Creation of graphs and analysis of the magnetic flux are performed in the accompanying software.

2.1 Key features

KROM helps you in your work through the following features:

Easy to use data collection and analysis application, avoiding time consuming data analysis.

Export of plots to scalable vector graphics format, SVG. Graphs in your reports are sharp.

Display of the magnetic flux density as:
o measured values
o absolute values
o averages per pole

Display of 1, 2, 3 or 4 rotor turns at a time, simplifying the detection of repeating patterns in
the magnetic field.

Measurements are performed at 10 kHz, providing 100 and 83 datapoints per pole at the elec-
trical frequencies of 50 and 60 Hz respectively.

Sensors that can be left in the airgap after measurements are completed, avoiding a second stop
for sensor removal. Leaving the sensors in place also makes it possible to perform a measure-
ment at a later date without disassembly of the generator.

3 Hardware

KROM consist of:


the flux meter instrument


hall sensors (six are included)

an optical sensor

a power supply

a USB cable

the KROM application (delivered on a USB-stick or preinstalled on a portable computer).
3.1 The flux meter instrument
The instrument has three main functions:

to provide the supply current required by the Hall sensors

to convert the analog signals from the Hall sensors and the optical sensor to digital signals

to transfer these digital signal to the computer.
Below follows a description of the layout of the instrument.
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