Oscilloscopes
Technicians use the visual display on a Oscilloscope to measure electrical values such as: __________, __________, __________
Voltage, frequency, & phase
The small amount of AC signal present on the output of a filtering network for a DC power supply is known as __________
Ripple
True or False:
Proximity sensors are usually three-wire, DC voltage sensors
TRUE
What is the dc output voltage in the handout drawing?
17.459 Volts
What components make up a VFD?
Rectifier Assembly ? DC Link ? Inverter
A graphical representation of an electric signal
Waveform
The half-wave rectifier contains __________
One diode
Three-wire DC sensors come in ________ and ________
PNP and NPN
A four-pole motor operating at 60 hertz has a base speed of ________ rpm
1800 rpm
What are the three acceleration curves used on a VFD?
Linear, Nonlinear, and S curve
Reduces the amplitude of a measure signal by a defined moment
Attentuation
The bridge rectifier contains __________
Four diodes
__________ sensors detect metallic objects
Inductive
After a VFD converts the incoming AC signal to rectified DC, what happens next?
The DC signal is then pulse width modulated (PWM) and filtered to feed a clean power signal to the motor
Can you run a 230-V motor on a 460-V VFD?
Yes! Set the V/Hz ratio to 3.83. That way the only way the motor will get 460 V is if the frequency is 120 Hz. At 60 HZ. the motor will get 230 V
Each little "box" on the oscilloscope grid is referred to as a __________
Division
A blown fuse in a power supply is most likely the result of __________
A shorted diode
A ____________ proximity sensor can reliably sense the exact position of a target that is coated with dirt.
Inductive
A 3-phase AC motor has a Volts/Hz ratio of 7.7. If the voltage applied is 346.5 V, what is the frequency?
45 Hertz
What is the purpose of boosting voltages at low frequencies?
To produce higher torque
It is always important to make sure the Oscilloscope is __________
Calibrated
What circuit would require the least amount of filtering?
Bridge rectifier
In the ____________ method, the emitter and detector are positioned opposite of each other.
Opposed sensing
What is the ripple voltage in the handout circuit?
309.55 mV
When a VFD is operated above 60 hertz, what happens to the HP and Torque?
HP remains at 100 percent and the torque decreases as the frequency increases