Power supply with cable in cable drum

Dear,

What is the crane KW ?

With 760 Mtr. Long cable, in inching mode of operations with drive motor, in rush currents of 8 - 12 times Ir shall cause an excessive voltage drop in the cable. This may reduce the starting torque , and frerquent faults with motor stalling may occur.

Assuming 4 * 16 sq mm Aluminium cable,

Conductor resistance at 70 deg. = 2.29 Ohms./km

Rated current = 51 Amps.

If you draw maximum of 51 Amps, for 760 mtr. cable ,

Volt drop before terminals of motor = (I * r * L)/(1.732*pf*1000)

Say pf = 0.55 during starting & 0.87 during normal running,

Starting volt drop = 51 * 2.29 * 760/ ( 1.732*0.55*1000) = 93 Volts.

I suppose, motor shall just stall.

Limit to crane motor : 3.7 kw rated motor shall work. with 760 mtr. long cable of 4* 16 sq mm size.

Similarly, you may work out for other applications.

Some people here at site, are of the opinion that this will cause excessive electrical stress in the drum. Hence this is hazardous.

They are right, even with a plastic or wood drum, even ignoring the additional volt drop due the the excessive cable length. There is a reason cable manufacturers don't recommend this.

Cut the cable to the proper length, when you are finished you can splice the cable back together using a proper cable joining kit (if you really have to). Personally I wouldn't want to have an easy-to-steal drum of 610m of copper cable just lying around next to the crane.

Leaving cable in the drum while that cable is under electrical load requires you first purchase a frying pan and some eggs. I like my eggs cooked in heaps of butter

If you are running the crane near capacity, the excess cable will become a giant electromagnet. Don't go near the cable drum with any metal in your pockets.

lol...I was just picturing an image of a set of dentures being ripped out of a worker's mouth as he passed by the drum

Made me laugh too - if if it happened to you would you look like this?

Mike

Good one!

Seeing CraziestOzzie's avatar and talk of losing teeth made me think of the animated film "Rudolph the Red-Nosed Reindeer" and the abominable cave monster when Hermie the elf had removed his teeth. I virtually became Hermie!

Mike

Some people here at site, are of the opinion that this will cause excessive electrical stress in the drum. Hence this is hazardous.

SETTING ASIDE THE VOLTAGE DROP, WHICH ALSO TRUE, EXCESSIVE CABLE HEATING WILL BE ANOTHER PROBLEM YOU MAY FACE. WITH 760 METER THE DRUM MUST BE ALMOST FULL. THE INNER MOST PART OF THE CABLE WILL NOT GET ANY MEANS FOR DESSIPATING HEAT.

IF CABLE IS KEPT IN DRUM, IT IS LIKE MANY CABLE TOUCHING EACH OTHER HORIZONTALLY AND VERTICALLY. NO CABLE DERATING FACTORS ARE AVAILABLE IN ANY APPLICABLE STANDARDS (INDIAN STANDARDS, BS7671 WIRING REGULATIONS ETC).

IT WILL NOT BE A MAGNET BECAUSE YOU ARE USING 4C CABLE AND 3PHASE CURRENT WITH NEUTRAL, FOR WHICH VECTOR SUM IS ZERO. NOLARGE MAGNETIC FIELD. SO NO MAGNET. NO DENTURES FLYING OFF.

lol...you funny bugger. You are indeed correct about the heat problem

Dear Mr. Prashant,

You can use it. But you will have voltage drop in this case. You can calculate voltage drop by using lenght of the cable and resistance per meter and Ampere.