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190 Series III
Users Manual
66
Motor Drive DC-Bus
The Motor Drive DC-Bus functions check the intermediate circuit of the motor drive.
XW Warning
To prevent possible electrical shock, fire, or personal injury, be aware that the
voltage that is present on the dc bus outputs remains on these outputs after the
motor drive is turned off. The amount of time depends on the internal impedance.
Voltage DC Level
The Voltage DC Level checks the value and stability of the internal DC-bus of the drive and
influence of braking or power feedback (if supported by the drive).
The readings show the dc level, as well as, the peak and peak-peak value. Use Voltage AC
Ripple for a closer look at the ac component.
The dc bus voltage should be about 1.414 times the rms line voltage, except when controlled
rectifiers (IGBT) are used in the input section. A dc voltage that is too low can trip the drive. Low
voltage can be caused by low input mains voltage or distorted input voltage by flat topping.
Tips:
• Use the RECORD function to check the dc voltage stability over time and detect slow
fluctuations. The test tool continuously records the digital readings of the measurements and
displays these as a graph.
• The TrendPlot graph rolls from right to left like a paper chart recorder. Observe that the
recorded time from start appears at the bottom of the screen. The present reading appears on
top of the screen.
Voltage AC Ripple
The Voltage AC Ripple function detects rapid fluctuations and ac components on the dc-bus.
Tips:
• A slight ripple can be visible and is load dependent. If the peaks of ripple have a different
repetitive level, one of the rectifiers could be malfunctioning.
• Ripple voltages >40 V can be caused by malfunctioning capacitors or the drive rating is too
small for the connected motor and load.
1.888.610.7664 sales@GlobalTestSupply.com
Fluke-Direct.com
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