Industrial Drive Applications Questions and Answers

Answer: A

How much of the year the load spends at each flow, combined with the cubic or proportional law for that load type, gives the annual figure. Estimating from the rated power alone can overstate the saving by an order of magnitude.

Answer: B

A machine that overheats or a saving that fails to appear both come back to what was assumed about the duty, and a written record makes that traceable. It also lets the study be reused when a similar application arises.

Answer: C

Everything else, efficiency included, is subordinate to serving the process, and a drive that saves energy while failing to make the product is worthless. Recognising that ordering is what keeps specifications sensible.

Answer: D

The drive holds whatever speed it is told, and the process loop decides what that speed should be from a measurement of flow, pressure, temperature or tension. Separating the two loops in bandwidth is what keeps the arrangement stable.

Answer: A

Torque needed at the bottom of the range, thermal duty over the cycle and the accuracy actually required are the three things most often assumed rather than established. All three are cheap to check before purchase and expensive to correct afterwards.

Answer: B

Ramp times that feel slow, a stop that is not quite level, or a noise nobody anticipated are all outside a specification written in torque and speed alone. Talking to the people who will operate the plant is what catches them.

Answer: C

The extremes of the cycle are where a marginal design shows itself, and recorded currents and temperatures give a baseline against which later trouble can be judged. Disabling protection to get through commissioning stores up a much worse failure.

Answer: D

Correct answer: the equivalent current to be checked against the rating

A varying duty is assessed by computing the root mean square of the current over the cycle and comparing it with the machine’s continuous rating. Recording the actual current after commissioning replaces the design estimate with a measurement, which either confirms the sizing or reveals that the duty is heavier than assumed.

Answer: C

An electric car has a battery to store the energy, an inverter to convert the DC of the battery into AC for the motor, an electronic control unit to control the drive and charging, and an electric traction motor. It has no internal combustion engine, which is the part found in petrol and diesel cars and in the hybrid. The answer is option C.

Answer: D

An electric car has low carbon emission at the point of use, a high energy efficiency (a motor and battery turn most of the stored energy into motion) and low maintenance because it has fewer moving parts, no engine oil and no exhaust system. These are all real advantages.

But charging a battery takes much longer than filling a tank with petrol or gas, which takes only a few minutes, so a shorter refuelling time is not an advantage of an electric car. The answer is option D.