Motor Protection dv/dt and Sine Wave Filter Solutions:

At the output end of variable speed drives, the pulse width modulated (PWM) pulses from the inverter stage unless filtered (Sine Wave filters, dV/dt filters) or impedance limited by chokes, can severely shorten motor life. The new MTE A Series of filters can be supplied for both 415 volt and 690 volt VSD systems and high current optional ratings up to 1,600 amps are possible. Units can be supplied as IP-00 open panel or with various cabinet options.

MTE dV/dt filters

MTE Series A dV/dt filters are designed to protect AC motors from the destructive effects of peak voltages caused long cable runs between the inverter and motor. Depending on the switching time of the power semiconductor used in the inverter and the size of the motor, cable lengths as short as 2 metres can result in motor peak voltages that exceed the rating of the motor’s insulation system. However, the longer the cable the greater the problem. The MTE dV/dt filter is provides no more than 150% of bus voltage with up to 300 metres cable between the filter and the motor. It is also rated for a maximum dV/dt of 200 volts per microsecond. The dV/dt filter has a “3% insertion impedance” which ensures motor torque is not affected by added voltage drops from the filter.

MTE Series A dV/dt filters are designed for use with inverters operated at switching frequencies between 900 Hz and 8 kHz. The dV/dt filter has a continuous current rating of 100% RMS and intermittent current of 150% for 1 minute and 200% for 10 seconds.

MTE Sine wave filters

MTE Series A sine-wave filters provide a sine-wave output voltage when driven from PWM inverters with switching frequencies from 2 kHz to 8 kHz. For drive applications, these filters eliminate the problem of motor insulation failures and reduce electromagnetic interference by eliminating the high dV/dt associated with inverter output waveforms. Harmonic voltage distortion feeding a transformer at full load and at 60 Hz is 5% maximum. Harmonic voltage distortion feeding a motor at full load and at 60 Hz is 5% typical.