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PDF copies of the paperwork supplied with our standard 1-3 reg PSUs


1 Reg Paperwork (1-3 amp power supplies)
2 Reg Paperwork (4-6 amp power supplies)
3 Reg Paperwork (7-10 amp power supplies)

Aux Relay Paperwork for our 1-5amp relay boards.

Mains Current Drawn


PSU Mains Loads Chart

To contact Technical Support click here.


Useful Formulae:



Disclaimer: The information provided here should be used for reference only. These formulae do not take into account any margin of error or environmental influence which may manifest in the working world. KT Assemblies Ltd. cannot be held responsible for any miscalculation derived from using the information presented on this page.

NEW!! Use our real-time calculator here.
This calculator is based on Ohm's Law.
IF YOU KNOW NEED TO KNOW
VOLTS ÷ OHMS = AMPS
VOLTS ÷ AMPS = OHMS
VOLTS x AMPS = WATTS
WATTS ÷ AMPS = VOLTS
WATTS ÷ VOLTS = AMPS
AMPS x OHMS = VOLTS

RESISTANCE OF THE LENGTH OF CABLE x CURRENT
DRAWN 		= VOLT DROP
------------------ OHMS ----------- AMPS



Heat Dissipation


To work out the amount of heat radiated from a PSU (in Watts) use the following formula:
Output Current x Output Voltage x 70%

For example a 2 amp power supply at 24 volts would be:
2 x 24 x 70% =
48 x 70 % = 33 Watts

If standby batteries are being used then add 20 Watts to the total:
33 + 20 = 53 Watts.


Volt Drop Table

Current carrying capacities and associated voltage drops for twin and multicore P.V.C insulated cables, non- armoured (copper conductors).


Also available as a printable PDF

BS6006 & BS6346

Conductor operating temperature 70°C

Conductor cross sectional area Installation methods A to C† of table 9A ('enclosed') Installation methods E to H of table 9A ('Clipped direct') Installation method K of table 9A ('Defined conditions')
One twin cable. With or without protective conductor single phase
AC or DC.
One three-core cable, with or without protective conductor, or one four core cable phase one One twin cable. With or without protective conductor single phase
AC or DC.
One three-core cable, with or without protective conductor, or one four core cable phase one One twin cable. With or without protective conductor single phase
AC or DC.
One three-core cable, with or without protective conductor, or one four core cable phase one
  Current carrying capacity Volt drop per amp per metre Current carrying capacity Volt drop per amp per metre Current carrying capacity Volt drop per amp per metre Current carrying capacity Volt drop per amp per metre Current carrying capacity Volt drop per amp per metre Current carrying capacity Volt drop per amp per metre
1 2 3 4 5 6 7 8 9 10 11 12 13
mm² A mV A mV A mV A mV A mV A mV
1.0 14 42 12 37 16 42 13 37        
1.5 18 28 16 24 20 28 17 24        
2.5 24 17 21 15 28 17 24 15        
 
4 32 11 29 9.2 36 11 32 9.2        
6 40 7.1 36 6.2 46 7.1 40 6.2        
10 53 4.2 49 3.7 64 4.2 53 3.7        
16 70 2.7 62 2.3 85 2.7 70 2.3        
                         
25 79 1.8 70 1.6 108 1.8 90 1.6 114 1.8 95 1.6
35 98 1.3 86 1.1 132 1.3 115 1.1 139 1.3 122 1.1
50         163 0.92 140 0.81 172 0.92 148 0.81
  AC / DC   AC / DC  
70         207 0.65/0.64 176 0.57 218 0.65/0.64 186 0.57
95         251 0.48/0.46 215 0.42 265 0.48/0.46 227 0.42
 
120         290 0.40/0.36 251 0.34 306 0.40/0.36 265 0.34
150         330 0.32/0.25 287 0.29 348 0.32/0.25 302 0.29
185         380 0.29/0.23 330 0.24 400 0.29/0.23 348 0.24
240         450 0.25/0.18 392 0.20 474 0.25/0.18 413 0.20
300         520 0.23/0.14 450 0.18 548 0.23/0.14 474 0.18
400         600 0.22/0.11 520 0.17 632 0.22/0.11 548 0.17

† For installation Method C, the tabulated values are applicable only to the range up to and including 35mm². For larger sizes in this installation method, see ERA report 69-30. For cables in ducts in the floor of a building, the ERA ratings must be adjusted by the appropriate factor for the ambient temperature.

The current carrying capacities in columns 6 and 8 are applicable to flexible cables to BS 6004 Table 1(b) where the cables are used in fixed installations.



Correction Factors

For Ambient Temperature

Ambient temperature 25°C 35°C 40°C 45°C 50°C 55°C 60°C 65°C
Correction factor 1.06 0.94 0.87 0.79 0.71 0.61 0.50 0.35


Sample Formulae for the Volt Drop Table


FORMULA = LENGTH X VOLT DROP X AMPS = VOLT DROP OVER LENGTH
1.0 mm TWIN CABLE FORMULA = 42 MV PER AMP PER METER      
10 metres at 5 amp with 1.0mm twin = 10 x 5 x 42 = 2100 mv
1000 		2.1 volts
20 metres at 5 amp with 1.0mm twin = 20 x 5 x 42 = 4200 mv
1000 		4.2 volts
30 metres at 5 amp with 1.0mm twin = 30 x 5 x 42 = 6300 mv
1000 		6.3 volts
50 metres at 5 amp with 1.0mm twin = 50 x 5 x 42 = 10500 mv
1000 		10.5 volts
75 metres at 5 amp with 1.0mm twin = 75 x 5 x 42 = 15750 mv
1000 		15.7 volts
100 metres at 5 amp with 1.0mm twin = 100 x 5 x 42 = 21000 mv
1000 		21 volts
 
1.5 mm TWIN CABLE FORMULA = 28 MV PER AMP PER METER      
10 metres at 5 amp with 1.5mm twin = 10 x 5 x 28 = 1400 mv
1000 		1.4 volts
20 metres at 5 amp with 1.5mm twin = 20 x 5 x 28 = 2800 mv
1000 		2.8 volts
30 metres at 5 amp with 1.5mm twin = 30 x 5 x 28 = 4200 mv
1000 		4.2 volts
50 metres at 5 amp with 1.5mm twin = 50 x 5 x 28 = 7000 mv
1000 		7.0 volts
75 metres at 5 amp with 1.5mm twin = 75 x 5 x 28 = 10500 mv
1000 		10.5 volts
100 metres at 5 amp with 1.5mm twin = 100 x 5 x 28 = 14000 mv
1000 		14.0 volts
 
2.5 mm TWIN CABLE FORMULA + 18mv PER AMP PER METER      
10 metres at 5 amp with 2.5mm twin = 10 x 5 x 17 = 850 mv
1000 		0.85 volts
20 metres at 5 amp with 2.5mm twin = 20 x 5 x 17 = 1700 mv
1000 		1.7 volts
30 metres at 5 amp with 2.5mm twin = 30 x 5 x 17 = 2500 mv
1000 		2.5 volts
50 metres at 5 amp with 2.5mm twin = 50 x 5 x 17 = 4250 mv
1000 		4.2 volts
75 metres at 5 amp with 2.5mm twin = 75 x 5 x 17 = 6375 mv
1000 		6.3 volts
100 metres at 5 amp with 2.5mm twin = 100 x 5 x 17 = 8500 mv
1000 		8.5 volts
 

MINIATURE CIRCUIT BREAKERS FOR USE IN CONJUNCTION WITH MOTOR STARTERS AND TRANSFORMERS

  Table 2-1 phase 240V AC DOL starting
Motor starters
In general miniature circuit breakers can give only short circuit protection to motor loads due to high starting currents which may be encountered: typically 3 to 12 times full load current (FLC)

Assumptions
The tables give recommended mcb ratings for motors up to 37kW based on the following assumptions:

Direct on-line starting
starting current = 7 x FLC
run up time =
6 seconds, motors < 3 kW
10 seconds, motors < 22 kW
running currents = average values only
(individual manufacturers figures may vary)
four pole motors i.e. speed approx.
1500 rev/min.

For Higher inertia loads i.e. hoists and fans run up times maybe considerably longer than those assumed above. The rating of the mcb must take account of the greater run-up time and starting current. The required mcb rating can be determined by reference to time/current curves (consult us)

Star/ delta starting
Since, during the changeover from star to delta, a high current surge in the order of DOL values may be met, the mcb rating selected should be the same as that
recommended for DOL starting

KW Hp Running C60H C60HC C60HD NC100C NC100D
0.12 0.166 0.55 2 1 1    
0.18 0.25 0.7 2 1 1    
0.25 0.33 0.87 2 2 1    
0.37 0.5 1.35 4 2 2    
0.55 0.75 1.55 4 2 2    
0.75 1 1.93 6 4 2    
1.1 1.5 2.5 6 4 4    
1.5 2 3.5 10 5 6    
2.2 3 4.8 16 10 10 10 10
3 4 6.4 16 16 10 16 10
3.75 5 7.8 20 20 16 20 16
4 5.5 8.1 25 20 16 20 16
5.5 7.5 11 25 25 16 25 16
7.5 10 14.4 32 25 20 25 20
9.33 12.5 17.3 40 32 20 32 20
11 15 21 50 40 25 40 25
13 17.5 25 63 50 32 50 32
15 >20 28 63 50 40 50 40
18.5 25 35   63 50 63 50
22 30 40   63 50 63 50
30 40 54     63 80 63
37 50 65.5       100 80
Table 2-1 phase 240V AC DOL starting
KW Hp Running C60H C60HC C60HD NC100C NC100D
0.12 0.166 0.95 2 2 1    
0.18 0.25 1.5 4 2 2    
0.25 0.33 1.7 6 2 2    
0.37 0.5 3 10 6 4    
0.55 >0.75 4.5 16 10 6 10  
0.75 1 5.5 16 16 10 16 10
1.1 1.5 8.5 20 20 16 20 16
1.5 2 10.5 25 25 20 25 20
2.2 3 15.5 32 32 25 32 25
3 4 20 40 40 32 40 32
3.75 5 24 50 50 40 50 40
5.5 7.5 34 63 63 50 63 50
6.3 8.5 36.5   63 63 63 63
7.5 10 45     63 80 63
11 15 66.5       100 80

  VA Primary
in (A) 		C60H C60HC C60HD NC100C NC100D
Transformers
High inrush currents are also produced when transformers are switched on. Typically 10-15 times full load current.

Assumptions
The tables give recommended mcb ratings for single phase transformers up to 12500 VA and three phase transformers up to 30000 VA on the following formula.

Mcb rating
15 x normal current of transformer
min instantaneous tripping
cc efficient of mcb

500 0.7 4 2 1    
750 1.04 6 4 2    
1000 1.39 6 4 2    
2000 2.78 10 10 6 10  
5000 6.95 32 16 10 16 10
10000 13.89 50 32 20 32 20
15000 20.84   50 32 50 32
20000 27.78   53 40 63 40
25000 34.73     50 80 50
30000 41.67     63 80 63
Table 4 - 1 phase transformers 240V AC supply
VA Primary
in (A)		 C60H C60HC C60HD NC100C NC100D
50 0.21 1        
100 0.42 2 1 1    
250 1.04 6 4 2    
500 2.08 10 6 4    
1000 4.17 20 10 10 10 10
2500 10.42 40 25 16 25 16
5000 20.84   50 32 50 32
10000 41.67     63 80 63
 


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