Mining, in this context, means the classic underground mining industry, which loosens rock from the deeper layers of the earth using heavy equipment like excavators, rock bolter machines, dump trucks or tunneling vehicles. Sometimes it is necessary to use electric mining vehicles when exhaust gases from combustion engines should be avoided because of danger of suffocation or danger of explosion in a tunnel. Battery electric vehicles are then used, or electric vehicles fed by long motor cables longer than 300 meters.

Working principle

To reduce exhaust gases in tunnel environments special mining vehicles are driven by inverter-fed electric motors. These specialized vehicles typically have a two-level voltage source inverter and an electric motor which drives direct the wheels or indirect via hydraulic pipes. The inverter switches the DC link voltage via a pulse width modulation on the motor cable to easily change frequency and voltage amplitude of the fundamental voltage waveform. The electric motor can be controlled from zero up to full rotor speed and can supply the requested torque.

Damaging effects

Due to the voltage switching in the inverter, these steep voltage pulses are the reason for some high frequency effects. They cause some disadvantages like voltage overshoot at the motor terminal, bearing currents in the motor and generation of electromagnetic noise conducted and radiated.

The Solution

Our Blueferrite nanocrystalline cores are a high impedance to common-mode currents. Mounting the cores at the inverter output over the three motor phases U, V, W, they will reduce the common-mode currents and therefore also circulating and rotor-to-ground bearing currents to a harmless current level. The core sizes, quantity of cores and the magnetic properties must be adapted on the respective application, mostly depending on rated power and motor cable length. Our selection guide and engineering people will help you to find the right cores for your application.

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