Variable Frequency Drive Flashcards
A motor operated with a VFD is subject to voltages higher than the peak of the line. T or F?
True
What can high frequency from a VFD do to a motor?
Bearings can become pitted and may prematurely wear out
Create induced current in the rotor corr causing overheating
What are the three induction motors that can be used with VFDs?
Inverter Ready
Inverter Duty
Vector Duty
A reluctance motor is what type of motor?
Non-induction
Name 4 advantages of VFD’s
Energy Savings
Reduced Noise
Reduced Maintenance Cosrs
Control Flexibility
VFDs are often controlled by _______________ like the type used in a PC.
Microprocessors
What distorts the voltage and current waveforms?
Harmonics
Why does a VFD produce harmonic distortion?
Its a result of high frequency solid state switching in the drive.
What is the limit of THD allowed and what must be done if the THD is to high on the line side?
3%, and if to high, filtering on the line side of the VFD can be accomplised with an input line reactor.
VFD’s are best operated in what temperature range?
10 and 40 degrees celsius
Control wiring of a VFD is, at minimum a Class _ wiring method.
Class 1 wiring method
How many pulses does a Three Phase, Full-Wave rectifier have? And how many degrees out of phase are their supply voltages?
18-Pulses
20 degrees out of phase, provided by a phase shifting transformer
A dc Link section in a VFD is compromised of what?
An inductor in series with the output, and a capacitor in parallel with the output.
An IGBT is a semiconductor consisting of an _______, _________ and a ____________.
Emitter
Gate
Collector
What motor speed control technique is the lowest cost and requires no feedback?
V/Hz Control
