Deck 8: Overload Units

Question 1

What is the best way to assure adequate protection for an overload unit?

Answer 1

The absolute best way to assure adequate protection is to consult the cover of the motor starter, the motor control center, or the manufacturers catalog at the time of installation.These are the instructions given by one manufacturer: when the overload heater size is selected from the table on the inside of the motor starter cover, the nameplate full load amperes current of the motor is used without applying any multipliers.

Question 2

When the melting alloy is a solid, the shaft of the ratchet wheel is held from turning.

Answer 2

True

Question 3

It is important to understand that each different type of overload protection method requires its own _______________.

Answer 3

procedure

Question 4

When the bimetallic strip is heated, the metal with the lower thermal expansion characteristic will become longer, and cause the metal strip to bend.

Question 5

The most common type of overload unit is the electronic overload unit.

Question 6

The overload unit contacts are connected in parallel with the motor starter contactor unit control coil.

Question 7

Overload units utilize the motor load current to mimic the _______________ characteristics of the motor being protected.

Question 8

Overload protection is designed with inverse time-delay trip characteristics.This means the ____ the overload current the faster the circuit will open, but a smaller overload would take much longer to open the circuit.

A)average
B)smaller
C)shorter
D)greater

Question 9

What are the three most common types of overload units?

Question 10

Thermal overload units conduct the motor load current through heater elements.

Question 11

A bimetallic strip is used as a(n) _______________ lever.

Question 12

Overload units are designed to help energize a motor that is building up excessive heat.

Question 13

The absolute best way to assure adequate motor protection is to consult the cover of the motor ____, the motor control center, or the manufacturers catalog at the time of installation.

A)starter
B)compressor
C)gasket
D)thermostat

Question 14

Electronic type of thermal overload units are adjustable for a range of motor load currents, and are set for the full load amperes (FLA) of the specific motor load.

Question 15

The _______________ unit is operated by heat developed from the motor load current going through the overload heaters.

Question 16

Overload units are designed with an inverse time-delay function.

Question 17

The three most common types of overload units are the melting alloy (eutectic), bimetallic, and _______________.

Question 18

The thermal overload unit of the motor starter is located below the ____ contractor.

A)spring
B)magnetic
C)load
D)overhead

Question 19

Electronic motor overload units ____ the motor differently than either the melting alloy or the bimetallic overload units.

A)charge
B)deactivate
C)induce
D)protect

Question 20

The eutectic alloy in the heater barrel element is a material that goes from a solid state to a liquid state without going through an intermediate ____ stage.

A)gas
B)plasma
C)putty
D)magnetic