Motor starter ladder diagram help

Thread Starter

Hmagers04

Joined Feb 12, 2016
10
I just need someone to verify that I'm completing my assignment correctly. I have not yet included line and cross-reference numbers on the diagram so disregard that i'll work on it later. This is what needs to be included in my ladder diagram..

A 3-phase motor is to be protected against phase loss, phase imbalance, or low voltage using a Square D MPS type relay. The motor is to be controlled from a START/STOP PB station that also contains a green pilot light to indicate the status of the MPS relay. The MPS is to be supplied power form the line side of the starter. Include line and cross-reference numbers on the diagram.
The green status light should be ON when the 3-phase, 240-volt motor circuit and the MPS are energized. The motor is not to be started unless the status light is illuminated. This ON status indicates that a phase reversal has not occurred in the circuits on the line side of the starter.

Available equipment list:
Motor starter
- With holding contacts - 240 VAC coil -1NC/1NO Aux. contacts

START/STOP PB station
- With 12 VDC green light
240/480 x 120/240 V transformer
MPS relay with 240 input
120 VAC to 12 VDC power supply
- With battery backup
Control relay – 12 VDC
- 2NC/2NO sets of contacts
 

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MaxHeadRoom

Joined Jul 18, 2013
20,860
Initially puzzled why you have the motor contactor on the power side rather than control circuit side of the transformer?
It would be customary to use a 120v or control voltage value version rather than the 240v supply type.
Max.
 

Thread Starter

Hmagers04

Joined Feb 12, 2016
10
Thats why I find it a little confusing....I dont understand how im supposed to have a 12vdc pilot light light up when the 240v MPS is energized
 

MaxHeadRoom

Joined Jul 18, 2013
20,860
The secondary of the transformer is 120v and you also have a contact across that, there always has to be a load (output) shown for any logic string otherwise it is a dead short.
Prmary and secondary should also sh0w fusing.
Refer to some of the Dwg's in the PDF.
Max.
 

MaxHeadRoom

Joined Jul 18, 2013
20,860
Incidentally the string with the CR relay in is shown wrong, the coil always is shown as the last in the string, and not in series with another output, light, loads can be shown in parallel but always at the end.
Max.
 

MaxHeadRoom

Joined Jul 18, 2013
20,860
I will give the once over, but off the bat there are errors again with contact in rungs without outputs, and unlabeled!.
It is now considered bad practice to place an O/L in the opposite side to the coil.
It is mainly when the right side rail is a grounded neutral, but it still pays to keep all logic on one side of the output.
In most case the X1 terminal would be grounded to set up a local neutral. But not mandatory.
Also the use of a bridge is not necessary if you place the light on the 12v DC side of the circuit.
You have been given a 12dc ind light.
Max.
 
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