Jump to content

Electrolyte Strength


twosheds

Recommended Posts

Does anybody know how to measure/work out strenght of electrolyte in Liquid Resistor starter

 

we currently use an AIOP System to control the start and run a 8000 hp motor driving a mega shredder shredding scrap

 

 

the motor runs with a 8 % fixed slip when its running

 

 

 

Link to comment
Share on other sites

Electrolyte type and strength is dependant upon a number of factors including tank size/volume, start torque and start time, number of consecutive starts to hot, number of starts per hour, ambient temperature, whther the unit is fitted with a heat exchanger etc etc. The fact that this unit is operating in slip control mode also needs to be taken into consideration.

 

I therefore suggest you speak to AOIP or distributor. If you have the above information handy, it will make it easier for them to provide you with the guidance needed.

 

Regards,

GGOSS

Link to comment
Share on other sites

thanks for info perhaps i did'nt explain problem well enough see below

 

The main reason for trying to get some sort of benchmark for the solution when the system was set up 25 kg of electrolyte salt was added as per nameplate we had touble with the solution overheating after many phone calls to manufacturer it was decided to add an extra 75 kg of electrolye salt

we have changed the electrodes recently (worn out after 4 years service) and refilled tank with water and 100 kg of salt since then we have had trouble with motor tripping out with overcurrent

 

any thoughts would be appreciated

 

 

 

Link to comment
Share on other sites

  • 4 weeks later...

That dosage sounds extremey high. Which EPM starter model do you have installed? Also, by motor runs at 8% slip, do you mean the starter is always in circuit with electrodes partly separated eg no rotor shorting contactor or are you achieving that via external fixed resistors? Also, is your starter fitted with a heat exchanger?

 

We do quite a bit of work here with metal recyclers and have starters installed on shredders to approx 5,000hp. The dosage used is different to that of a standard starting arrangement because the electrodes are always in circuit and the electrolyte is hot thereby giving a different characteristic. In these installations the electrodes are manually controlled eg the machine operator keeps a closeful watch on shredder loading and drives the electrodes in or out subject to conditions at the time. That process can be automated and whilst I do not fully understand they don't do that, it's keeping people in a job so who am I to argue that.

 

The starters I refer to are not AOIP EPM, use a different type of electrode configuration and movement strategy. The electrodes can be moved from the fully seperated to fully closed positions and vice versa in a very short period of time and are therefore well suited to shredder applications. Operators here drive them very hard, 4 years service life from electrodes from a starter used in this manner is unheard of!

 

Back to your over-current trip issue this could well be related to the electrolyte mix or just a shredder operation/loading issue. I'll run your issue past a couple of people I know here and if there's anything I can add I will come back to you.

 

Regards,

GGOSS

Link to comment
Share on other sites

  • 1 year later...

Hi,

 

I have a similar problem as that resently. We have this 400hp/415Vac wound rotor that we have put back into commision yesterday after 7 years. It has a liquid resistance starter connected from the rotor output to the liquid tanks and to the short out contactor.

 

The problem is that when we start it we actually have to wind down the electrodes to a point where their are almost totally submerged then the torque is achived to lift the load. Together with this we have some sparking around the electrodes then the drive takes off to about 75% speed before we have to close the starpoint shorting out the resistance to raise the speed to synchronous speed.

 

I am really not sure weather it is that the resistance may be too high or is it the electrolyte as we are using normal tap water?

Due to this I had to remove the "resister fully lowered limit switch" which closes the starpoint and control it through a normal flush switch just to get the drive started because normally the drive should start to move while winding down slowly the rpm picks up but this only happens when the electrodes is almost totally submerged.

 

Any suggestions or has anyone faced a problem like this? I have bought some Sodium carbonate to mix with the water today and give it another try tommorow to see if there are any changers. This is the same set up that had been used previously to run this drive. Any ideas on the mix ratio of the electrolyte?

Link to comment
Share on other sites

Does anybody know how to measure/work out strenght of electrolyte in Liquid Resistor starter

 

we currently use an AIOP System to control the start and run a 8000 hp motor driving a mega shredder shredding scrap

 

 

the motor runs with a 8 % fixed slip when its running

hi

this is shailendra awasthi , working in cement grinding unit. in india

i can give a example in my plant we are using L.R.S BHEL MAKE FOR 1500KW SLIP RING MOTOR

We maintain its electrolyte ph value 13-13.5, for trouble free starting,

i don't know exatly relation between slip & elecrolyte ph value.

i know that this is not complite answer for Q but it can help you up to some extent.

Link to comment
Share on other sites

  • 3 months later...
Hi,

 

I have a similar problem as that resently. We have this 400hp/415Vac wound rotor that we have put back into commision yesterday after 7 years. It has a liquid resistance starter connected from the rotor output to the liquid tanks and to the short out contactor.

 

The problem is that when we start it we actually have to wind down the electrodes to a point where their are almost totally submerged then the torque is achived to lift the load. Together with this we have some sparking around the electrodes then the drive takes off to about 75% speed before we have to close the starpoint shorting out the resistance to raise the speed to synchronous speed.

 

I am really not sure weather it is that the resistance may be too high or is it the electrolyte as we are using normal tap water?

Due to this I had to remove the "resister fully lowered limit switch" which closes the starpoint and control it through a normal flush switch just to get the drive started because normally the drive should start to move while winding down slowly the rpm picks up but this only happens when the electrodes is almost totally submerged.

 

Any suggestions or has anyone faced a problem like this? I have bought some Sodium carbonate to mix with the water today and give it another try tommorow to see if there are any changers. This is the same set up that had been used previously to run this drive. Any ideas on the mix ratio of the electrolyte?

 

Drop me an email simonturfrey@aol.com and I will be able to assist

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...