1ph vs 3ph

[Mead Camans]

Hello all,

I'm looking at the Sedgwick TA315 table saw for regular heavy duty work and I notice it comes in both single phase and 3 phase, both with the same performance ratings and price. Forgive me if this has been addressed a million times before, but what exactly is the difference? It would certainly be easier for me to have the single phase version wired in in my current establishment, but what (if anything) would I be missing out on by not getting the 3 phase version?

Saw in question:

Sedgwick TA315 Table Saw Bench 1ph 4.0 hp

The Sedgwick TA315 Sliding Table Bench Saw is a British engineered and built cast iron table saw bench which represents excellent value for money. The saw is driven by a high powered and quiet 4hp induction motor that will run reliably, day in, day out in trade workshops.It has a large...

www.scosarg.com

Cheers,

George

 

[Yojevol]

3 phase electricity is the basic supply that is generated in our power stations and fed out onto the national grid at very high voltage. The voltage is reduced in stages until it is at a suitable level to be fed into your local distribution system. It is also broken down into 3 single phases for domestic use as this allows wider availability to more homes.
If you only have a normal 1ph supply then a 3ph machine will not work.
Even with your 1ph supply you will need to check that your cabling and fuse box are man enough to supply the heavy start-up current on switching on the saw.
3ph saws are also available for those premises, eg factories, which have a 3ph supply for running heavier machinery.
Brian

 

[johnnyb]

the difference between single phase and three phase is a three phase motor spins in perfect sympathy with the generator. ìt needs no extras to have a phase shift. that usually means no neutral only three lives. across any live the voltage is 415v. what single phase means is just a single live from a 3 phase supply. because single phase isn't balanced like three phase(in a motor) a neutral wire is used. this usually means three phase motors are much more reliable and often have a bit more oomph(one more kick)

 

[johnnyb]

between any live and neutral the voltage is 240v

 

[Sideways]

If you have 3 phase available, a 3ph motor is better (electrically simple, more reliable in the long term, potentially a little better balanced for minimal vibration) but it's not a big difference and may not be noticed for years. Most users won't care.
Reselling the used machine in future, single phase machines tend to be preferred by domestic buyers.
But - it's a 3kW motor with a significant startup surge. In domestic terms it's a big saw. No one is going to run it off a 3 pin domestic plug. It will need a dedicated circuit and breaker in the distribution board.

 

[Sandyn]

3 phase runs sweeter, quieter motor (but probably not so noticeable when actually cutting), power is more balanced when running. It's like a 6 cylinder and a 4 cylinder engine. Both get you from A to B, but the 6 cylinder just sounds smoother ( I think). In use I don't think you will notice, they both cut wood and you will have ear defenders on.
You already say it would be easier to have single phase wired and I think single phase will keep it's price better, because so many people are looking for them.

 

[mccpe]

I have a single phase TA315. It is a fantastic bit of kit. The 3 phase motor might be slightly better for the reasons above, but the single phase won’t disappoint for power, noise or smoothness.

 

[johnnyb]

absolutely. but it may disappoint when the caps leak in a few years!

 

[smackie]

3 phase motors are generally more efficient once you get above a few HP. They also usually require less amps at startup (as you‘re spreading the load across the 3 phases). That has implications for the supply wiring size, which might be important depending on the site.

 

[sploo]

I'm a big fan of the HuanYang VFDs (220V 3KW 13A 4HP Variable Frequency Drive VFD Huanyang Inverter High Precision 720355349004 | eBay). They're easy to set up, and it would allow you to power a 3 phase machine from a single phase supply.

The configuration options means you can choose the ramp up and spin down times (i.e. bring the motor up to full speed over 2 seconds); which significantly mitigates the big inrush current issues that can pop fuses and trip MCBs. I have three machines rated at 3hp running from standard UK mains plugs with no problems.

At 4hp you might need to run it from a dedicated 16A line, but if you have an accessible consumer unit in your workshop then that's pretty simple to set up.

I believe you get the benefits of a smooth 3 phase motor, with the ease of running from a single phase mains with these; though I assume they consume some power; such that maybe the overall efficiency isn't as good as a dedicated 3 phase supply. However, a 3hp single phase motor has a decent chance of popping a 13A fuse on startup (due to the large inrush current), so if you went with 4hp single phase you'd definitely be needing a dedicated single phase mains line from your consumer unit anyway (possibly 20A or more).

 

[smackie]

However, a 3hp single phase motor has a decent chance of popping a 13A fuse on startup (due to the large inrush current), so if you went with 4hp single phase you'd definitely be needing a dedicated single phase mains line from your consumer unit anyway (possibly 20A or more).

I’d definitely go for the dedicated 20A if you go down this route along with paying careful attention to the breaker type (as it will affect the trigger point). Definitely worth the money for a good electrician here who‘s done some commercial work IMO.

 

[Mead Camans]

Thanks for the info everyone. Really gtreat stuff. Erring more towards the 1ph at the moment, but good to have the clarification.

George

 

[Sandyn]

Is it possible to give the three phase and single phase a test drive, then see if you notice any difference?

 

[Mead Camans]

Is it possible to give the three phase and single phase a test drive, then see if you notice any difference?

That's a fair point. Might be worth seeing if a dealer could help with that.

 

[Sandyn]

I'm sure they would. What a saw!!!! I'm jealous, lol

 

[Claud1]

I have both single phase and 3 phase in my shop and would not be without 3 phase but I have owned a single phase TA 315 for about 20 years and find it unbelievable when it comes to power I cannot fault it ( I can't speak of the later machines ) I have also tried a inverter and would not go down that route again at any cost.

 

[sploo]

I have both single phase and 3 phase in my shop and would not be without 3 phase but I have owned a single phase TA 315 for about 20 years and find it unbelievable when it comes to power I cannot fault it ( I can't speak of the later machines ) I have also tried a inverter and would not go down that route again at any cost.

Inverter as an a VFD, or something else? What issues have you found with them? Unfortunately I don't have a 3 phase supply so VFDs are my only choice.

 

[Claud1]

Inverter as an a VFD, or something else? What issues have you found with them? Unfortunately I don't have a 3 phase supply so VFDs are my only choice.

I can't remember the details but it cost me around £1,400 about 10 years ago it did the job ok but wasn't as powerful as mains 3 phase and the continuous humming noise did my head in. I only kept it around 10 months. Modern ones may be a lot better I wouldn't like to say but I will never regret getting 3 phase installed

 

[Spectric]

For a workshop enviroment it is three phase all day long, plenty of power and as mentioned three phase motors just work, this is because you have a rotating magnetic field which means they self start. Single phase need capacitors to produce a phase shift between voltage and current to start them. As far as the end user is concerned they would not be able to tell the difference between two machines both with say a 3Kw motor. But if you do not have three phase then get the single phase and appropriate 16 amp socket rather than pursue the convertor/invertor route. If you do have three phase then is it long term or could you end up elsewhere with just single phase in which case you would wish you had brought the single phase.

 

[Sideways]

I'm sure they would. What a saw!!!! I'm jealous, lol

They're not bad. A big single ended trunnion pinned to the bottom of the table is quite sturdy and I like their rip fence but they are a pig to do serious maintenance on and the factory paintwork is shameful.
Wadkins are better designed for strength and maintenance.
Startrite's have better sliders but are not as robust.