Reversing Motor Starters Flashcards Preview

Electrical Lab MCSC Period 2 SAIT-Alberta > Reversing Motor Starters > Flashcards

Flashcards in Reversing Motor Starters Deck (8)
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1

What does any basic reversing motor starter consist of?

Two contactors and an overload device.

2

How would someone reverse the direction of a three phase squirrel cage induction motor?

Interchange any two of the three phases.
Nema standards interchange lines 1 and 3.

3

In a reversing motor starter, what are the holding contact terminal numbers:
For a NEMA starter?
For an IEC starter?

2 and 3 for forward, 4 and 5 for reverse.

13 and 14 for both.

4

How would one prevent a dangerous short between line 1 and line 3 on a reversing motor starter?

By the use of a mechanical interlock, allowing only one armature to seal in at a time.

5

Why do reversing motor starters use electrical interlocks? How is this achieved?

To prevent coil energization, in the event that the opposite coil is already energized. It is achieved by placing a normally closed contact of the opposite coil, in series with the original coil.

6

There are seven circuit sections in which to place interlock contacts in a reversing motor starter, what are they?

General stop.
Forward stop.
Reverse stop.
Forward start.
Forward holding.
Reverse start.
Reverse holding.

7

What is the purpose of pushbutton interlocking?

To allow the change in rotation of the motor with the use of one button, and to not require a general stop first.

8

How many physical pushbuttons are present in a general reversing motor starter circuit, utilizing push button interlock? How are these labelled?

There are three only. The "Stop" button, "Fwd start" button, and the "Rev start" button.