Self tests Flashcards
List two types of manual motor starters
toggle switch
push-button
Besides stopping and starting a motor, a motor starter provides ___________ protection?
overload
The contacts of a motor starter are horsepower rated. Briefly explain what this means?
contacts can interrupt the starter ring in rush current or locked rotor current of the motor
What part of a simple manual motor starter senses an overload current drawn by the motor?
the heater element of the overload relay
A melting-alloy type of thermal overload relay is called a?
solder-pot relay
An overload relay that uses a strip of two dissimilar metals is called a ?
bimetallic relay
What is meant by the term low-voltage protection?
Control device that drops out on low voltage but does not automatically pickup once voltage is restored
Toggle switch starters are usually limited to a maximum rating of _______ hp.
8
List three methods of guarding the exposed live parts of a motor, as described in the Canadian electrical code?
Electrical room (vault)
Elevation beyond 2.5m above floor
Guard rail (or fence)
Identify two important safety steps you must take before starting work on a motor branch circuit?
Disconnect power source
lock out and tag disconnecting means
How can you protect your face and eyes from arcs and flashes when you close a motor switch?
turn head away when operating switch
Before energizing a motor, it is advised first to test electrically with a _________?
megger
Besides electrical shock, a motor also represents a __________ hazard. To reduce this risk, __________ are usually installed.
mechanical
guards
list three functions, other than stopping and starting a motor, that a motor controller can provide?
speed control
sequential control
reversing operations
remote control operations
what is the fundamental difference between a magnetic contactor and magnetic motor starter?
a magnetic motor starter consists of a magnetic contactor AND a overload relay protection
what is the difference between the power circuit and control circuit of a motor starter?
power circuit = main line contacts
control circuit = electromagnetic coil and auxiliary contacts
what are two basic parts of a thermal overload relay?
heater element and normally closed auxiliary contact
A three phase motor requires an overload ________ in series with each of the line conductors to the motor?
heater
Selection of the heater is based on the full-load ____________ of the motor, which is easily determined from the ________ of the motor?
current
nameplate
Before an OLR can be reset, time must be allowed for it to _____________?
cool down
