The ranking below comes from systematic counting of publicly discussed failures in mining engineering communities. It reflects what operators talk about, which is not the same thing as a warranty database — frequently-discussed failures skew toward the ones that are puzzling or expensive rather than the ones that are merely common. Read it as a map of operator concern, not as failure statistics.

Rank Failure type Mentions Share Equipment affected
1 Overheating 489 21.3% All motors
2 Demagnetisation 364 15.8% Permanent-magnet machines only
3 Vibration 202 8.8% All rotating equipment
4 Lubrication problems 186 8.1% Bearing related
5 Bearing failure 114 5.0% All rotating equipment
6 Power quality (VFD related) 111 4.8% Variable-speed drive systems
7 Corrosion 101 4.4% Wet or chemically aggressive environments
8 Contamination (dust, water ingress) 75 3.3% Failed seals
9 Cavitation 55 2.4% Slurry and other pumps
10 Short circuit 35 1.5% Windings

Demagnetisation is the entry that changes selection

Sintered NdFeB magnets work up to roughly 150 °C; beyond that, demagnetisation is irreversible. Nothing on this list is more specific to permanent-magnet machines, and nothing is easier to design out before the order than after installation.

Rotor construction is the lever. Interior permanent-magnet (IPM) rotors resist demagnetising conditions better than surface-mounted (SPM) designs. That is a specification to settle with the supplier during selection — mine sites put motors near mill bearings and inside enclosed electrical rooms, and both run hot.

A bearing case worth reading

A new large ball mill showed persistently low feed-end bearing shell pressure from the no-load stage onward. Loading to 50% ball charge with water roughly doubled the pressure differential, while oil temperature and running noise both stayed normal. Inspection traced it to out-of-tolerance machining of the bearing shell locating keyway, which prevented the shell from self-aligning. After 400 hours at 80% load the operator elected to run to failure under delivery pressure, and the manufacturer later replaced the bearing housing.

The value here is not that a particular manufacturer had a problem. It is that the mill feed-end bearing sits in the drivetrain between motor, gear reducer and mill shell, and a tolerance defect there shows up as a symptom that looks electrical or hydraulic long before anyone suspects machining. Alignment checking, bearing housing tolerance control and coupling design are the stages where this gets prevented.

Failure mode to design response

Failure type Common cause Selection or design response
Overheating High ambient, poor cooling, overload Match motor to load properly; leave insulation-class temperature margin
Demagnetisation Hot environment; rotor topology wrong for duty Thermal design plus magnet topology chosen for the actual duty
Vibration Misalignment, bearing wear, machining tolerance Alignment verification, bearing housing tolerance control
Lubrication and bearing failure Insufficient lubrication, dust ingress, VFD shaft currents Upgraded sealing, insulated bearings, automatic lubrication
Contamination Seal failure under dust or water IP65/IP66 with labyrinth sealing

Verified retrofit results on slurry duty

Application Replacement Previous motor Savings
Slurry pump retrofit TYP315M-6, 90 kW Y315M-6, 90 kW 18–20%
Slurry pump retrofit TYP225M-6, 45 kW Y225M-6, 45 kW 18–20%
Overflow pump replacement TYP225M-6, 45 kW Y225M-6, 45 kW 21.8%

Variable-speed operation also reduces impeller wear by softening hydraulic shock, which is a substantial part of the case for permanent-magnet drive on slurry duty — the energy figure alone understates it.

Note: these are LEADGO’s own measured project results. Customer identification has been withheld pending release approval.