Line C VFD & ECM Operation Flashcards
A VFD or variable frequency drive is also know by what other names?
Variable speed drives, adjustable drives, adjustable frequency drives, frequency converts
What are some of the reasons why we would want to adjust motor speeds?
Save energy (improve efficiency), Match the speed to process requirements, match the torque to process requirements, lower noise levels, reduce mechanical stress, and improve working environment.
What are some applications where a gas fitter may see a VFD used?
DFMA, pumps, fans, compressors
What process takes AC power and turns it into DC power in a VFD?
The converter phase, also known as rectification.
AC-DC –DC– DC-AC
converter DC BUS Inverter
What smooths out the DC power in a VFD?
The DC bus phase
AC-DC –DC– DC-AC
converter DC BUS Inverter
What is the phase called were the DC power is turned back into AC power called?
The inverter phase
AC-DC –DC– DC-AC
converter DC BUS Inverter
Why do we go through the process of changing AC power to DC power and then back to AC power?
This is done so that we can control the frequency (hertz) and voltage and in this way better control the motor.
What electrical component is used to rectify the AC power and convert it into DC power?
Diodes
How is the DC power smoothed out during the DC bus phase?
Through the use of capacitors which add energy to the DC waveform when voltage drops
What is used to change the DC power back to AC power?
IGBT (insulated gate bipolar transistors)
For what two reasons is an overcurrent protection device required in the AC supply to the VFD?
- To provide thermal protection for the VFD cables between the location of the overcurrent protective device and the VFD
- To limit the energy available at the location of a short circuit
What four conditions can present issues for VFDs?
- No Flow conditions
- High speed response
- Full load conditions
- Equipment speed limitations
What is main difference between the motors of a VFD and an ECM?
The ECM is a DC motor whereas the VFD is an AC motor.
What type of current and how many phase is an ECM?
The power produced is 3 phase DC output
What is the most common use of EC motors in the gas fitting world?
Fans: air-handlers, ventilation fans, furnace fans
