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Variable-frequency drive: Quiz


Question 1: Low voltage units are typically designed for use with motors rated to deliver 0.2 kW or 1/4 ________ (hp) up to several megawatts.
Fuel oilShoe sizeHorsepowerISO/IEC 646

Question 2: An embedded ________ governs the overall operation of the VFD controller.
Reduced instruction set computerCentral processing unit64-bitMicroprocessor

Question 3: As new types of ________ switches have been introduced, these have promptly been applied to inverter circuits at all voltage and current ratings for which suitable devices are available.
Condensed matter physicsQuantum mechanicsPhysicsSemiconductor

Question 4: The main microprocessor programming is in ________ that is inaccessible to the VFD user.
BIOSRead-only memoryFirmwareOperating system

Question 5: Introduced in the 1980s, the ________ (IGBT) became the device used in most VFD inverter circuits in the first decade of the 21st century.
Insulated-gate bipolar transistorBipolar junction transistorPower MOSFETPower semiconductor device

Question 6: Much of the same logic contained in large, powerful VFDs is also embedded in small ________ such as those commonly used in computer fans.
Electronic speed controlBrushless DC electric motorInduction motorElectric motor

Question 7: In addition to this simple volts per hertz control more advanced control methods such as vector control and ________ (DTC) exist.
Electrical generatorLinear motorDirect torque controlElectric motor

Question 8: This starting method typically allows a motor to develop 150% of its rated ________ while the VFD is drawing less than 50% of its rated current from the mains in the low speed range.
TorqueEnergyForceAngular momentum

Question 9: Thus the ________ of volts per hertz must be regulated to a constant value (460/60 = 7.67 V/Hz in this case).

Question 10: A small amount of braking torque is available to help ________ the load a little faster than it would stop if the motor were simply switched off and allowed to coast.


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