Figure 300-55 presents a generalized curve of speed versus horsepower for Class A machines based on one vendor’s experience. Figure 300-56 shows the distribution of driver types for Class A compressors, again based on one vendor’s experience.
Refer to the Driver Manual for detailed application information, and use the following general comments for any preliminary work:
1. Synchronous motors are 3–4% more efficient than induction motors of the same speed, and usually offer power factor improvement for the electrical system. High-efficiency induction motors should not be used with reciprocating compressors, because the oscillating torque causes excessive heat. Rather, use standard induction motors.
2. Steam and combustion gas turbines can be applied to reciprocating compressors, although it is not a frequent practice (see Figure 300-57). A torsional analysis is essential to be certain the train will not operate close to a torsional critical speed.
3. Spark-ignited gas engines are available to drive Class B machines up to about 2000 HP at 900–1000 RPM.
4. Belt-drive systems can be used up to about 200 HP.