View Full Version : wiring primary resistor start for soft starter
01-16-2010, 05:31 PM
hello guys , i am in a bit of a mess, need help from good motor control guys here hopefully by monday morning, have a slip ring 6lead motor that "was" wired for primary resistor start, slipring is motor w brush assembly on back end powered up though resistors and dropped out slowly til motor is up to speed, all the time the main contactor is in l1 l2 l3 is in , the problem is , the resistor starting circuit has all been gutted from panel , i now have a soft starter on l1 l2 l3 , but motor wont turn over ,runs at a slow speed as if windings are incomplete low amperage in this state,but quiet, i have tried configuring star ,with other 3 leads, with very noisy!! motor, and very!! high amps! , not turning over ,with every possible ramping and voltage seting tried w soft starter, the question is what do i have to do w/ the remianing 3 leads for slip ring leads a startup , power them up to turn over THEN BRIDGE? OR POWER UP TO TURN OVER THEN DROP OUT? its also questionable that soft start may be sized right on edge 55kw(70 hp) exact same motor specs, w a motor requiring high torque starting, 6 ft blower wheel, 4 b-belt driven very large supply air fan, ANY HELP PLEASE W EXPERIENCE , greatly appreciated, time is of escence, thank you stan
01-16-2010, 09:49 PM
I don't think that what you have is a primary resistor start, but a wound-rotor motor that has to have the rotor circuit resistors in a wye connection pattern through the controller to produce enough torque to start (and run). I will not be so bold as to say that it can't be made to work, but I've never seen that type motor hooked up to a soft start. There's no way to connect the rotor leads that I know of, so that enough rotor current can be created to start the motor. All that we ever retro'ed had the motor replaced with a standard induction motor. Hope somebody else has better news for you, but the rotor circuit is an integral part of starting that motor.
01-17-2010, 03:49 AM
Pretty much everything you need to know.
01-17-2010, 08:58 AM
thank you both for replies especially for pdf ,thats great, I see now that it will be necessary to wire in resistor circuit again, next question, anyone have line and control schematics for this system? :D busy week ahead! regards thanks again stan
01-17-2010, 01:10 PM
Electrical motor controls third edition, by Gary Rockis and Glen Mazur. Page 421 Figure 15-20 has the schematic you are looking for. I am computer challenged and don't have a scanner or I would post it here. Maybe someone reading this will help out. Good Luck .
01-18-2010, 05:47 PM
will be putting in standard 3 phase motor this week, one more starter of this fashio still on site able to keep running , thanks for responses , stan
Powered by vBulletin® Version 4.2.0 Copyright © 2013 vBulletin Solutions, Inc. All rights reserved.