Page 44 - Industrial Power Engineering and Applications Handbook

Theory, performance and constructional features of induction motors 1/25
Table 1.12 Normal systems of cooling for totally enclosed large machines
~~ ~
First characteristic Description Second characteristic Description
number to indicate number for means of
the cooling system supplying power to
circulate the coolant
1 2 3 4
0 Free circulation of the coolant from the 0 Free convection: No external power source
machine to the surrounding medium is essential. Heat dissipation is achieved
through natural convection like a surface
cooled motor
I Inlet pipe-circulation: The coolant flows to 1 Self-circulation: Movement of the coolant
the machine through inlet pipes from a source is normally through a fan mounted on the
other than the surrounding medium and then rotor shaft, like a normal fan cooled motor
freely discharges to the surrounding medium (Figures l.lS(a)-(d) and 1.19(a) and (b)
(as in the use of separately driven blowers)
Outlet pipe circulation: The coolant is drawn 2
from the surrounding medium but is discharged
remotely through the pipes
Inlet and outlet pipe circulation: The coolant 3
flows from a source other than the surrounding
medium through the inlet pipes and is
discharged remotely through the outlet pipes
J Frame surface cooled (using the surrounding 4
medium): The primary coolant is circulated
in a closed circuit and dissipates heat to the
secondary coolant, which is the surrounding
medium in contact with the outside surface of
the machine. The surface may be smooth or
ribbed, to improve on heat transfer efficiency
(as, in a TEFC or tube ventilated motor (Figures
1.19 and 1.20)
5 Integral heat exchanger (using surrounding 5 Circulation by integral independent
medium): As at No. 4 above, except that the component: Like a fan, driven by an
medium surrounding the machine is a heat electric motor, and the power is drawn from
exchanger, which is built-in as an integral part a separate source. rather than the main
of the machine like a totally enclosed. tube- machine itself
ventilated motor (Figure 1.20)
6 Machine-mounted heat exchanger (using the 6 Circulation by independent component
surrounding medium): As at No. 5 above, mounted on the machine: As at No. 5
except that the heat exchanger is neither above, but the movement of the coolant ia
externally mounted nor forms an integral part through an intermediate component and
of the machine. Rather it is mounted as an mounted on the machine and not an integral
independent unit, directly on the machine part of the machine
(Figures 1.21 and 1.22)
Integral heat exchanger (not using the 7 Circulation by an entirely separate
surrounding medium): As at No. 5 above, system: As at No. 6 above, but the
except that the cooling medium is different circulation of the coolant is by an entirely
from the surrounding medium. It can be liquid independent system, not forming a part of
or gas the main machine in any way and mounted
separately like a water-distribution system
or a gas-circulation system
Machine-mounted heat exchanger (not using 8 Circulation by relative displacement: As
the surrounding medium): As at No. ‘6’ above at No. 0 above, except that instead of
except that the cooling medium is different surface cooling the cooling is achieved
from the surrounding medium. It can be liquid through the relative movement of the
or gas (Figures 1.21 and 1.22) coolant over the machine
Separately mounted heat exchanger: The 9 This numeral is used for circulation by
primary coolant is circulated in a closed circuit any means other than stated above
and dissipates heat to the secondary coolant.
It can be a heat exchanger as an independent
unit separately mounted