Zero Crossing SSR's

Status
Not open for further replies.
fifty60

fifty60

Senior Member
Location
USA
Are zero crossing SSR's devoid of electrical noise? Also, can someone please recommend a cable shield to place between two bundles of power wires (one bundle is 460V and the other is 115V) they have to cross, thankfully at a 90 degree angle, but I was hoping to have a shield to place between the bundles at the 90 degree crossing.
 
Last edited:
gar said:
140916-0853 EDT

This discussion, http://www.crydom.com/en/Tech/Newsletters/Solid Statements - SSRs switching types.pdf , should answer part of your question. Generally it is a good presentation. However, I would differ with some of the statements.

Your shielding question needs more information relative to why do you care.

.
Click to expand...
I agree, the final conclusions at the end of that were not correct to my thinking. Then after I thought about what their likely context was, it made more sense; they are only referring to single phase motor loads turning on across-the-line with the SSR when they stated that phase angle should not be used for motors. 3 phase soft starters of course are ALWAYS phase angle control! They should have been more precise, but considering that Crydom are mostly used by bit bangers, it seems they are considering their audience.

Fifty60,
As to noise, consider this; turning a relay or contactor coil on will create noise, as will the contact closures themselves. A zero cross SSR creates less noise, at least in terms of amplitude. But if used for proportional control, then the frequency (rate) of the lower noise disturbances will increase, which may be a different concern. There is no free lunch. That's likely why gar asked you what you were concerned about, because you will usually trade one issue for another, so your application determines which issue is better to live with.
 
fifty60 said:
.... Also, can someone please recommend a cable shield to place between two bundles of power wires (one bundle is 460V and the other is 115V) they have to cross, thankfully at a 90 degree angle, but I was hoping to have a shield to place between the bundles at the 90 degree crossing.
Click to expand...

In regards to EMI. shielding just part of a cable does no good. In fact a non-continuous shield can increase the noise coupling between the cables. Routing the cable crossing at 90 degrees can be very effective. Maintaining physical separation between the cables provides some, little, benefit. More-so at higher frequencies.
 
starbolin said:
Routing the cable crossing at 90 degrees can be very effective. Maintaining physical separation between the cables provides some, little, benefit. More-so at higher frequencies.
Click to expand...
If the current carrying wires in each bundle are twisted and the bundles cross at 90 degrees, then even a modest separation of the two bundles at the crossing point (a few wire spacings or so) will make a big difference in signal injection via mutual inductance or capacitance.
 
GoldDigger said:
If the current carrying wires in each bundle are twisted and the bundles cross at 90 degrees, then even a modest separation of the two bundles at the crossing point (a few wire spacings or so) will make a big difference in signal injection via mutual inductance or capacitance.
Click to expand...

Maybe I'm just displaying my ignorance here, but the OP said they were power cables. Why would anyone care about noise in power cables?
 
gadfly56 said:
Maybe I'm just displaying my ignorance here, but the OP said they were power cables. Why would anyone care about noise in power cables?
Click to expand...
Most commonly because one power wire is connected to a noisy device (like an SCR dimmer) and the other is feeding power to noise sensitive equipment which does not have adequate input filtering.
Or so that the second bundle does not radiate the noise somewhere else along its path?
 
Yes, the end goal here would be to minimize any noise getting out through the equipment power lines. The SSR controls a heater load, that is time proportioned over a 2 second period. The most it will turn on and off over a 2 second period would be 1 time.

For my sub panel I have line voltage (typically 230V or 480V), separate 110VAC, 24VDC, and some RS485, RS232, and Ethernet communications. My number one area to minimize noise would be the communications wiring. After that would actually be the noise that is getting out on my power lines.

Twisting all of the 110V wires together would definitely decrease the noise on the wires, but not really a concern right? I don't think it would decrease the noise going out on the wires. For my power supply, which takes the 110V as input and gives me a 24VDC output, I would want to minimize the noise coming in on that particular wire because it will affect the 24VDC output?

As for my 24VDC, would I want to twist together all of the V+ and V- wires together to reduce common mode noise?
 
Status
Not open for further replies.
Top