Deck 15: The Three-Phase, Wound-Rotor Induction Motor

Question 1

Provide two considerations that must be taken into account when selecting NEMA or IEC standards for installations.

Answer 1

Consider the following when selecting NEMA or IEC standards for installations:
• How much expertise do you need to make the proper selection?
• Do you want to dedicate the increased space usually needed for NEMA controllers?
• Do you have a good understanding of the application?
• If you are replacing an existing installation, what other components have to be changed?
• How much is cost a factor compared to interchangeability?
• Are overloads adjustable or changeable?
These questions, along with the difference in price, must be considered when determining the proper selection.

Question 2

____________________ are resistors that change resistance due to thermal effects.

Answer 2

Thermistors
Thermal resistors

Question 3

The programmable parameters of a digital controller must be set when installing a new electronic drive.

Answer 3

True

Question 4

IEC standards can be used to select the most suitable controller; the IEC philosophy is that ____________________ is a critical part of the selection process.

Question 5

A typical ____________________ is an electronic circuit type of sensor that produces a small magnetic field at a radio frequency (RF).

Question 6

____________________ controls, which use a variety of devices to detect the presence or absence of light, are used where physical contact is not needed or desired.

Question 7

A simple vector drive is fairly accurate but does not use much feedback from the motor, whereas a PWM drive has tighter control and more feedback from the motor operations.

Question 8

Rather than using a direct connection to the motor through a speed sensor to control the output to the motor, a(n) ____________________ measures the different components of the current delivery to the motor.

Question 9

The International Electrotechnical Commission (IEC), headquartered in Geneva, Switzerland, is a counterpart to the National Electrical Manufacturers Association (NEMA).

Question 10

Briefly describe two considerations when selecting a starter for a particular motor drive situation.

Question 11

The capacitive proximity sensor has an advantage over the inductive sensor in that it can detect both nonmetallic and metallic objects.

Question 12

Briefly explain the difference between the pulse-width-modulation (PWM) method of controlling output voltage and motor current, and the flux vector method of controlling the output to the motor.

Question 13

Name two important considerations when determining the proper photoelectric device to use.

Question 14

The least complicated photoelectric sensors are called direct-scan sensors. Although they are harder to keep in alignment, they are used extensively.

Question 15

What are two limitations of the capacitive sensor?