Quasi wave to Sine wave converter / with a 10-20 Volt boost. 1

[ZAMMAN]

I have a (CATV) Cable system that is currently running on existing 90/15A power supplies (modified /Quasi sine wave). I have to re-power the system adding additional equipment that will require higher inputs. The problem is that I am hitting (input) the new equipment with a 75 VAC / 5 amp load (Quasi). My specs indicate that I need a minimum of 85 VAC / 4 amp (Sine wave) at the input of this equipment.

- Is there any equipment that would take a range of 75-84 VAC (quasi) and convert it to Sine while giving me a higher +10-20 VAC (sine) gain and a 4 amp max output.

 

[Lewish]

What's wrong with using a step-up transformer?

It's a cheap solution and works well with most quasi-sine sources. You may need to have them custom fabricated, but if you need a dozen or more, they should be less than $10.00.

 

[ZAMMAN]

Lewish,

Will a step-up transformer convert quasi to sine as well as boost the voltage?

 

[Lewish]

It can. It really depends on how many steps are in the quasi and how you specify the transformer. You want to spec it so that it looks as much like a choke as it does a transformer if you want good sine output.

 

[ZAMMAN]

Lewish,

I'm not much of an electrical guy. I just know that I have to have a certain voltage and amperage at the end point, so what do you mean when you say choke?

 

[Lewish]

I guess I am showing my age again. A choke is just an inductor used to smooth out the waveform. If the transformer is wound as a pure transformer, your output voltage waveform will look like your input. But if it is wound more as a choke, it will smooth the steps in the quasi waveform to look more like a true sinewave.
All power supplies have chokes in them, if they have filters on the output side.
The EMI line filter on the AC side of a power supply is just a fancy choke with a capacitor across it.

Hope that helps.

 

[ZAMMAN]

Lewish,

So knowing this we probably can convert quasi to sine at the power supply location prior to sending it down the cable to the unit.

- Can we then remove/bypass this EMI line filter on the PS output and replace it with one that works more like a choke (as you mentioned).

- Do you know of a unit(manufacturer) that can be used in conjunction with the exisiting PS/quasi wave output for an externally (field) application? Or does this have to be a custom order?

- Will the output of the new sine wave be degraded in any way.

 

[Lewish]

Hi Zamman, Yes, I would convert the quasi to sine before sending it down the cable. This would make your whole installation quieter.

You would do this by adding a passive low-pass filter at your power supply. Don't change anything about the power supply, just add the filter outboard.

Without knowning exactly what your quasi looks like and not knowing your frequency of operation, 50 or 60Hz or some other frequency, I can't really tell you much about what the filter needs to be.

Give me more info and I will see what I can do.

 

[ZAMMAN]

Lewish,

Sorry for the late reply, but the operating Frequency that is currently being used is 60Hz. As for a shot of what the quasi sine wave looks like, I'm working on it, I hope to have something tomorrow. Would you happen to have an idea of the size (dimensions) of what a filter may have?