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Q6. What design factor limits the maximum torque of a d-c motor? Of an a-c motor? A shunt motor runs on no load at 700 r/min off a 440 V supply. The resistance of the shunt circuit is 240Ω. The following table gives the relationship between the flux and the shunt current: Calculate the additional resistance required in the shunt circuit to raise the no-load speed to 1000 r/min.

Shunt current (A)
0.5
0.75
1.0
1.25
1.5
1.75
2.0
Flux per pole (m Wb)
6.0
8.0
9.4
10.2
10.8
11.2
11.5