Reversing Motor Starters 030204g Flashcards
What are the basic components of a reversing motor starter?
A contactor for operation in the forward direction.
A contactor for operation in the reverse direction.
An overload relay.
How many power contacts are required for a basic reversing magnetic motor starter?
6 total.
3 for forward and 3 for reverse.
How many holding contacts are required for a basic reversing magnetic motor starter?
One for forward and one for reverse.
How does a NEMA reversing magnetic motor starter reverse the direction of a three-phase motor?
Interchanges L1 and L3.
How many overload relays are required in a three-phase reversing magnetic motor starter?
One with three responsive elements since there is only one motor.
What is the purpose of a mechanical interlock on a reversing motor starter?
Physically prevents both armatures from being closed at the same time to prevent a line to line short.
What NEMA sizes include a mechanical interlock as a standard?
NEMA size 00 to size 5.
On larger sizes they must be specifically requested.
What is the purpose of electrical interlocking?
Without an electrical interlock a current of 4 to 10 times would occur over the second coil and could cause it to burn out due to the armature being jammed by the mechanical interlock.
What is an electrical interlock in a reversing motor starter?
Two sets of normally closed contacts with one being controlled by each coil. When one coil is operated it will cause the circuit to be broken to the coil for the other direction to avoid coil burnout.
What are the NEMA terminals 2 and 3 for?
Holding contacts. Forward coil on a reverse motor starter.
What are terminals 3 and 6 for in a reverse motor starter?
The reverse normally closed contacts for an electrical interlock in the forward circuit.
What are NEMA terminals 4 and 5 for in a reverse motor starter?
Holding contacts for the reverse direction.
What are NEMA terminals 5 and 7 for in a reverse motor starter?
Normally closed contacts controlled by the forward coil in the reverse circuit.
What terminals on a NEMA starter are generally used for connections?
Terminals 1-5.
What terminals can be used for pilot lights in a reverse motor starter?
Can use terminals 6 and 7. Lights would be connected between 6 and L2 for the forward coil and 7 and L2 for the reverse coil.
What are terminals 13 and 14 for on an IEC motor starter?
holding contacts for both forward and reverse.
What are IEC terminals 21 and 22 for on a reverse motor starter?
Used for both the forward and reverse electrical interlock contacts.
What are IEC terminals A1 and A2 for for on a reverse motor starter?
Used for the forward and reverse coils.
What are the 7 sections in the control circuit of a NEMA reversing motor starter?
General Stop Circuit.
Forward Stop Circuit.
Forward Start Circuit.
Forward Holding Circuit.
Reverse Start Circuit.
Reverse Stop Circuit.
Reverse Holding Circuit.
What does placing contacts in the Forward or Reverse stop circuit do?
Affects the starting and stopping of which ever direction it is placed in.
What does adding contacts in the general stop circuit do?
Can prevent the motor from being started in either direction and will stop the motor if it is running in either direction.
What does placing contacts in the start circuit of either direction for the motor do?
Contacts are placed in series with the start button and can affect the motor being started only. Once the motor is running it will not affect stopping it.
What does placing contacts in the holding circuit of a reverse motor starter do?
Contacts placed in series with the holding contacts will affect the motor from continuing to run when the start button is released and can also stop the motor if it is running.
What type of operation do push-button interlocks have?
Break-before make operation.
What do push-button interlocks allow a motor starter to do?
Allows the motor direction to be reversed without pushing the main stop button first.
