• Motor Drive Analyzer, 4 Channel, 500 MHz with motor shaft and harmonics
• Guided testing with graphical step-by-step voltage and current connection diagrams
• Preset measurement profiles

Drive input

Measure input voltage and current to quickly see whether values are within acceptable limits by comparing the variable frequency drive’s (VFD), also known as a variable speed drive (VSD) or adjustable speed drive (ASD), nominal rated voltage to the actual supplied voltage. Then, check the input current to determine if the current is within the maximum rating and the conductors are suitably sized. You can also check whether the harmonic distortion is within an acceptable level by visually inspecting the waveform shape or by viewing the harmonics spectrum screen (MDA-550) with total harmonic distortion and individual harmonics.

Extended harmonic measurements

Excessive harmonics are not just a threat to your rotating machines but also to other equipment connected to the electrical power system. The MDA-550 provides the ability to discover the harmonics of the motor-drive but can also discover the possible effects of inverter switching electronics. The MDA-550 has three harmonic ranges, 1st to 51st Harmonics, 1 to 9 kHz and 9 kHz to 150 kHz giving the ability to detect any harmonic pollution problems.

DC bus

In a motor-drive the conversion of AC to DC inside the drive is critical, having the correct voltage and adequate smoothing with low ripple is required for the best drive performance. High ripple voltage may be an indicator of failed capacitors or incorrect sizing of the connected motor. The record function of the MDA-500 Series can be used to check DC bus performance dynamically in the operating mode while a load is applied.

Voltage modulation

Measurements of the Pulse Width Modulated signal are used to check for high voltage peaks which can damage motor winding insulation. The rise time or steepness of impulses is indicated by the dV/dt reading (rate of voltage change over time), this should be compared to the motor’s specified insulation. The measurements can also be used to measure switching frequency to identify whether there is a potential issue with electronic switching, or with grounding, where the signal floats up and down.

Motor input

Ensuring that voltage is being supplied at the motor input terminals is key, and the selection of cabling from drive to the motor is critical. Incorrect cabling selection can result in both drive and motor damage due to excessive reflected voltage peaks. Checking that the current present at the terminals is within the motor rating is important as over current conditions could cause the motor to run hot, decreasing the life of the stator insulation which can result in the early failure of the motor.