soft starters

infano

Member
Join Date
Apr 2009
Location
Nairobi
Posts
4
hi friends,
is there any form of soft starter that doesnt employ the use of thyristors?
if not i have designed an electronic equipment which varies the amplitude of ac power supplies without using thyristors. furthermore the device gives a clean complete sine wave at whatever amplitude you set. do we have such a device? is my 'invention' useful?
 
More Info Needed

infano

I do not know of a Soft Start which does not use thyristors.

You need to answer a few questions before I can determine how useful your device may be.

Is this device capable of running the motor continuously or would it only be used to start the motor? Is the output voltage in phase with the input voltage so a contactor could be used to bypass the device, after starting the motor, with a "bumpless" transition?

Can it handle high voltage and current? Soft Start thyristors are typically rated 1400-1800 volts and up to 2000 amps.

What is the line current waveform, particularly when the device is putting out full voltage (motor running at full speed)?

What is the efficiency of the device (how much heat does it produce)?

I don't think that having a clean sine wave while starting a motor is a particular advantage and once the motor is up to speed, the thyristors are turned on for the whole half cycle so the motor is receiving a clean sine wave at this time. What would be the advantages of using your device?
 
A device that can produce a clean sine wave of variable frequency and voltage would be extrememly useful, unless it is inefficient, bulky, or very expensive.
 
Not a dig but a question, Why use soft starts when VFD's are just as cheap and have more functions? I have been changing out all out soft starters with VFD's.
 
more info

hi friends,
thanx alot for your interest in my device.
now first, this equipment does not contain any reactive elements in it so the output voltage and current is in phase with the supply, unless the load is reactive.

two, this equipment does not in any way generate its own waveform or frequency. it simply changes an incoming ac supply to any amplitude u desire. its more like an 'ac potentiometer' made up of semiconductors.

three, wether the device is used for starting alone or for running is upon the user to decide. the rating of the device depends on the rating of the semiconductors used but i do know that the cost of production for this equipment is as low as 5 percent of a thyristor starter of the same rating! efficiency is about the same as thyristor switch. please advice more!
 
Smoke, while softstarters and VFD's are close in price up thru 10hp, that is certainly not the case as the hp goes above that. At 100hp, a VFD is about 4 times the cost of a softstarter and it diverges further above that.
 
$ Soft Start vs. VFD

I agree with DickDV. Recently finished a project with several 75 H.P. pumps/blowers. Softstarts were about the same price as a standard starter. Vfd's were about 4-5 times as high.
 
Not a dig but a question, Why use soft starts when VFD's are just as cheap and have more functions? I have been changing out all out soft starters with VFD's.

Soft starters control acceleration VFD’s control velocity. Also, try using an electromechanical brake that is wired with the motor while the drive is running below 50 Hz.
 
well, i came up with this device while reaserching on electronically synthesised sound. the idea was to damp these ac soundwaves so that the sound will die off slowly - like in a drum beat.
so i guess this device ( ac potentiometer) isnt useful to the electrical community so i will jst go on with my project (sound generation). thanx for your help fellows! :cry:
 
infano said:
well, i came up with this device while reaserching on electronically synthesised sound. the idea was to damp these ac soundwaves so that the sound will die off slowly - like in a drum beat.
so i guess this device ( ac potentiometer) isnt useful to the electrical community so i will jst go on with my project (sound generation). thanx for your help fellows! :cry:

Hey, don't give up on us now you've got our attention...

I'm guessing you don't want to get into details just yet for obvious reasons, but from the info you've provided your 'invention' seems to be quite a longshot. Prove me wrong, if you dare/can!


jlcannon said:
Soft starters control acceleration VFD’s control velocity. Also, try using an electromechanical brake that is wired with the motor while the drive is running below 50 Hz.

Any VFD has a 'running' control signal that can be used to power an electromechanical brake. I do hope you use something similar when you install a softstarter, rather than wiring the brake over the motor windings!
 
its real!

this isnt a fantansy sparkz! this device is there, i have it, now! am not jst writing for the sake of running this thread. if there is anyone who is taking me seriously he/she should contact me. unfortunately i wont be giving you the circuit diagram any time soon.
 

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