Page 241 - Applied Photovoltaics

and dissipation primarily determine the corresponding power handling capabilities,
with the consequence that these small, high efficiency motors can handle relatively
large amounts of power.
The Australian Greenhouse Office (2004) provides extensive public information
about motors, including a database of the characteristics of available motors and aids
for motor selection. Since 2001, there have been mandatory minimum energy
performance standards in Australia for three-phase electric motors from 0.73 to
185 kW, and all motors licensed for sale in Australia in that range are required to be
registered in a public database.
11.4.2 DC motors

Fig. 11.13 shows the cross-section of a two-pole DC machine. Crosses represent
current flowing into the page and dots represent current flowing out of the page.

Figure 11.13. Cross-section of a two-pole DC machine (Used with permission of
McGraw-Hill Companies, adapted from Fitzgerald, A.E., Kingsley C. Jnr. & Kusko,
A. (1971), Electric Machinery, McGraw Hill, Tokyo, Japan).

There are four basic types of DC motors:
1. The series DC motor, as represented by Fig. 11.14a, has the field windings
connected in series with the armature windings. This configuration has a
severe limitation when being driven directly by photovoltaic panels because a

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