Which thickness CY cable do I need for 1.5kW spindle?

[bee]

So my Kress died (can't complain, it has served me very well), and I decided to upgrade to a 1.5kW Chinese spindle. So far it's been a lot of work to install it, and I still haven't decided where to place the vdf, so I do hope the new spindle will be every bit as amazing as it's reputed to be.

And now I found out I need CY cable between the vfd and the spindle, so I have some re-wiring to do (through cable tracks, oh!)

My question is which would be the correct core thickness of that CY cable for my use: 0.75mm, 1mm, 1.5mm?

Bernard

[Clive S]

I would use 0.75mm or 1mm CY 4 core 0.75mm will be fine

[bee]

Thanks! I've ordered the 0.75mm because I it'll be a bit thinner and I assume nicer to handle.

[A_Camera]

Thanks! I've ordered the 0.75mm because I it'll be a bit thinner and I assume nicer to handle.

It is thinner and lighter but it should be 1.5mm2. 0.75mm is OK for control signals but actually too thin for the power.

[Clive S]

It is thinner and lighter but it should be 1.5mm2. 0.75mm is OK for control signals but actually too thin for the power.

I still think 0.75mm is fine the motor is 1.5Kw 3 phase and quite short. There are many people using that on this forum.

[Lee Roberts]

Here is a chart showing what each size is rated at:



Here is a list showing the watts to amps conversions:

WATTS TO AMPS CONVERSION

60 Watts = 0.26 Amp
100 Watts = 0.43 Amp
200 Watts = 0.87 Amp
300 Watts = 1.30 Amp
400 Watts = 1.74 Amp
500 Watts = 2.17 Amp
600 Watts = 2.61 Amp
700 Watts = 3.04 Amp
800 Watts = 3.48 Amp
900 Watts = 3.91 Amp
1000 Watts = 4.35 Amp
1100 Watts = 4.78 Amp
1200 Watts = 5.22 Amp
1300 Watts = 5.65 Amp
1400 Watts = 6.09 Amp
1500 Watts = 6.52 Amp
1600 Watts = 6.96 Amp
1700 Watts = 7.39 Amp
1800 Watts = 7.83 Amp
1900 Watts = 8.26 Amp
2000 Watts = 8.70 Amp
2100 Watts = 9.13 Amp
2200 Watts = 9.57 Amp
2300 Watts = 10.00 Amp
2400 Watts = 10.43 Amp
2500 Watts = 10.87 Amp
2600 Watts = 11.30 Amp
2700 Watts = 11.74 Amp
2800 Watts = 12.17Amp
2900 Watts = 12.61 Amp
3000 Watts = 13.04 Amp
3100 Watts = 13.48 Amp
3200 Watts = 13.91 Amp
3300 Watts = 14.35 Amp
3400 Watts = 14.78 Amp
3500 Watts = 15.22Amp

.Me

[Clive S]

Lee that is helpful but the chart does not show if the cables are in free space or bunched together in one sleeve as the cable will have to be derated when bunched because of heat build up.

Edit Lee the Watts to Amps conversion has to state the voltage I know you have it done at 230V

[Lee Roberts]

Lee that is helpful but the chart does not show if the cables are in free space or bunched together in one sleeve as the cable will have to be derated when bunched because of heat build up.

Edit Lee the Watts to Amps conversion has to state the voltage I know you have it done at 230V

OK, to clarify:

Cg represents the derating factor for grouping cables.

A cable with a current rating of 6 amp installed in trunking alongside other circuits, that's circuits not cables!, would now have a Cg value, the Cg value is 0.57.

This means the cable current rating becomes: 6 x 0.57, that's 3.42 amp.

To add to this, you should note that the grouping factors are based on assumption, the assumption that all of the cables in the group are carrying their rated current.

So, if however a cable is not going to be carrying more than 30% of its grouped current rating, that cable can actually be omitted from the group rating calculation...

...an example, if you've got lets say 6 circuits in a group of cables but 1 of those cables is known to be operating below the said 30% consistently, you can safely calculate the group on the basis that it only consists of 5 circuits.

Here are some correction factors for multicore cable:




OK Clive, how did I do?

.Me

[Clive S]

OK Clive, how did I do?

Fine Lee I was not taking the p#'@s I just thought that the Voltage had to be added etc for the sake of people with no knowledge of sparky stuff.

[A_Camera]

Lee, what works is not the same as what is safe and what is recommended.

https://en.wikipedia.org/wiki/Electr...United_Kingdom



That is a more realistic and better data, even if you step down one size, 1.5mm2 is what should be used. 0.75mm2 is for small desk lamps, not for motors. Then again, I know most people never really use their spindles at maximum load, so it is never really going to be a problem and in many cases even 0.5mm2 might be OK, but I think 1.5mm2 is the minimum if you want to play it safe. My 1.5kW is rated 8A and I am pretty convinced that saving on cable costs is not a good decision. Also, if you ever decide to use a vector controlled spindle you will notice that it pulls more current as well, so what is the point of under dimensioning the cable?