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Question: section 1151 24 a drive consists of a synchronous motor...

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Section 11.5.1) 24 A drive consists of a synchronous motor supplied by a simple voltage- source inverter which in turn is supplied from a controlled rectifier, as shown in the system of Fig. 11.36. The motor rating is 75 kW, 1200 r/min, 440-V (L-L), 60 Hz, three phase. Its magnetizing reactance at rated frequency is 2.2 Ω, and its losses are negligible. The field current ratio n is 12. The available utility supply is at 460 V (L-L), 60 Hz, and three phase.

(a) Determine the maximum value of motor speed up to which this drive (b) Assuming unity power factor operation, find the required field cur- (c) Suppose the speed is to be increased to 2700 r/min. If the rated stator can provide its rated value of torque. rent for the condition of (a). current of the motor is not to be exceeded, what is the maximum available torque and mechanical power at this speed? (d) What should be the field current for the condition of (c)? (e) What should be the firing angle of the rectifier to provide rated torque at a speed of 300 r/min?

mech Dual converter a Inverter Field supply SM αι 2 Converter logic Inverter logic nech Figure 11.36 Synchronous motor drive operating in open loop.

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