Gntech Other models

With a rated output of 2.2 kilowatts, the motor sits in a range that often drives smaller pumps, compressors or workshop machines. The figure 71 at the front of the type designation corresponds to a small, common frame size under IEC 60072 and fixes the shaft centre height and mounting dimensions.

In industrial motors of this kind the squirrel-cage rotor is standard, since it runs with little maintenance and needs no slip rings. The number of poles sets the synchronous speed: at 50 hertz, two-pole motors turn at 3,000 revolutions per minute, four-pole motors at 1,500 and six-pole motors at 1,000, each slightly reduced by slip. Protection ratings follow IEC 60529 and mounting arrangements IEC 60034-7, for example a foot-mounted IM B3 motor or a flange-mounted IM B5 type. Running it from a frequency inverter raises the demands on insulation strength.

When buying secondhand, the rating plate is worth checking first: output, voltage, frequency and connection type should be legible and suitable. Turned by hand, the bearings should run smoothly, without play or noise, while an insulation test with an insulation-resistance tester reveals damp or damaged windings. The fan cover and terminal box deserve a second look, since corrosion or broken ribs point to a hard working life. If the motor has been rewound, that is worth raising openly before buying.