Thermolec Application &Technical Notes - Manual (Page 8)

STEP 1 - (continued)
347 (277) V, Single Phase Power Supply
When capacities are below 7 KW at 277 V and 8 KW at 347 V Thermolec recommends the use of the
following arrangements to obtain the most economical cost for heaters and electrical distribution.
These voltages are generally derived
from a 600 (480) volts - 3 phase -
4 wire power supply.
A group of 347 (277) volt - 1 phase
heaters should be distributed as equally
as practical over the three phases in
order to keep current imbalance to a
minimum.
Neutral conductor should not be broken
by any switching or protective device, be
it internal or external to the heater.
347 / 600V
4 wire power supply
(also 277 / 480)
Equal distribution of heaters
Line Current
The table below shows line current per one KW capacity at various voltages. The following formulas apply:
Multipliers to calculate Line Currents
(Line current in amperes = Multiplier x KW capacity)
Example: The Line current for a 40 KW / 600V / 3 phases heater is : 40 x 0.96 = 38.4 amperes.
L1 L2 L3 N
600 V / 3 Ph
or
(480 V / 3 Ph)
4 wires
POWER SUPPLY
347V (277)
347V (277)
347V (277)
N
L1
N
L1
N
L1
L1 L2 L3 N
600 V / 3 Ph (or 480 V / 3 Ph)
4 wires
POWER SUPPLY
Group of 1 Ph 347 V (or 277 V)
Electric Heaters
Typical branch
circuit protection
and disconnecting devices
in order to keep current imbalance to a minimum.
Thermolec
Standard 120 208 208 220 240 240 277 347 380 380 416 416 480 480 600 600
Voltages 1 Ph 1 Ph 3 Ph 1 Ph 1 Ph 3 Ph 1 Ph 1 Ph 1 Ph 3 Ph 1 Ph 3 Ph 1 Ph 3 Ph 1 Ph 3 Ph
Multiplier
Amp./KW 8.33 4.81 2.78 4.55 4.17 2.41 3.61 2.88 2.63 1.52 2.40 1.39 2.08 1.20 1.67 0.96
Line Current Line Current
Single phase Three phase
Line Voltage Line Voltage
THREE EASY STEPS