Magnetic starters
What is the most common voltage used for control systems?
120 V
A controlled transformer has a primary voltage of 480 V and a secondary voltage of 120 V. The transformer has a power rating of 0.5 kVA. What is the maximum I'll put current of the transformer?
4.17
What a vantage is there in using combination starters?
A combination starter provides safety for the operator because the cover of the enclosure is interlocked with the external operating handle of the disconnecting means.
Current draw by motor is
An accurate measurement of motor load
A combination starter provides?
Disconnecting means, overload protection, short circuit protection
The magnetic starter is held closed?
Electrical magnetically
What is a magnetic line voltage motor starter?
Electromagnetic devices to provide soft convenient and economical means of full voltage starting and stopping motors.
The thermal really heating element is selected
From the motors FLA and a manufactures selection chart
When a motor starter coil is the energized?
Gravity and spring tension open contacts.
Thermal overload relays react to?
Hi ambient temperatures and excessive heating due to overload current
An AC magnet may hum excessively due to?
Improper alignment, formatted between contact surfaces, loose laminations.
The purpose of overload protection on the motor is to protect the?
Motor from sustained over currents.
If an operator push the start button on a three phase induction motor and the motor starts to him but not run the probable trouble is?
One fuse is blown and the motor is single phasing.
Motors may burn out because?
Overloads, high ambient temperatures, poor ventilation
The purpose of a shading coil on an AC electromagnetic pole tip is to
Prevent chattering
The number of magnetic starter polls refers to?
The number of power, motor, or load contacts.
When the reset button does not reestablish to control circuit after an overload the probable cause is
The overload heater is burnt out
AC magnets are made of laminated iron?
To reduce heating effect
If the motor starter is installed according to directions but will not start what is a common cause for the failure to start?
Tripped overload
What causes the AC home or chatter in AC electromagnetic devices?
Under voltage or the contact surface is misaligned.
What safety feature does the combination starter provide that individual motor starter assembly's do not?
When the disconnecting means is open all parts of the starter are accessible however the hazard is reduced because of the readily accessible parts of the starter are not connected to the power line.
