Question 1

Overload units are designed to open their contacts when the motor current reaches ____ of full-load current.&#10;A) 95% to 105%&#10;B) 105% to 115%&#10;C) 115% to 125%&#10;D) 125% to 135%

Accepted Answer

Overload units are designed to open their contacts when the motor current reaches 115% to 125% of full-load current. This helps protect the motor from damage due to excessive current.

Question 2

Each phase of a three-phase motor should be protected by an overload relay.

Accepted Answer

Each phase of a three-phase motor should be protected by an overload relay to prevent the motor from overheating due to excessive current.

Question 3

The bimetal type of overload operates very differently from the solder-melting type.

Accepted Answer

False

Question 4

The bimetal type of overload unit is used to a large extent on commercial and industrial air conditioning units.

Accepted Answer

The answer of The bimetal type of overload unit is...

Question 5

Since the overload unit must be sensitive to motor current, the heater of the overload relay is connected ____.&#10;A) above the motor&#10;B) in parallel with the motor&#10;C) below the motor&#10;D) in series with the motor

Accepted Answer

The heater of the overload relay is connected in series with the motor, which ensures that it will sense any increase in motor current and trip the circuit to prevent motor damage.

Question 6

The solder-melting type overload relay has two separate sections: the heater section and the contact section.

Accepted Answer

The solder-melting type overload relay does have two separate sections: the heater section and the contact section. The heater section contains the solder alloy that melts and causes the contacts to open when the current exceeds the rated value. The contact section contains the contacts that open when the solder melts, interrupting the circuit and protecting the motor from damage.

Question 7

Most overload relays are operated by ____.&#10;A) pressure&#10;B) pneumatic controls&#10;C) heat&#10;D) magnetism

Accepted Answer

Most overload relays operate based on the buildup of heat, which is caused by excessive current flowing through the motor. This heat causes a bimetallic strip within the overload relay to distort, which activates the relay and trips the motor starter. Pressure and magnetism are not typically used to operate overload relays, and while pneumatic controls may be used in some specialized applications, they are not as common as heat-based relays.

Question 8

The solder-melting type of overload relay has a set of small ____ that are intended to interrupt the current flow in the control circuit only.&#10;A) contactors&#10;B) auxiliary contacts&#10;C) programmable controllers&#10;D) timers

Accepted Answer

The small contacts referred to in the question are auxiliary contacts. These are designed to interrupt the current flow in the control circuit and protect the motor against overload. The other options (contactors, programmable controllers, and timers) are not directly related to the function of the overload relay in protecting the motor against overload.

Question 9

Overload relays will trip faster in hot weather than they will in cool weather.

Accepted Answer

Overload relays have a thermal element that responds to the heat generated by an overload. In hot weather, the ambient temperature is already high, which can cause the thermal element to trip earlier due to the additional heat load. In contrast, in cool weather, the ambient temperature is lower, which means that the thermal element may take longer to respond to the heat generated by the overload.

Question 10

Single-phase motors are generally protected with a small ____ reset overload.&#10;A) automatic&#10;B) electronic&#10;C) manual&#10;D) battery-powered

Accepted Answer

Single-phase motors are generally protected with a small automatic reset overload to protect them from overheating and burning out. This overload protection device automatically resets once the motor cools down.

Deck 22: Overloads