HVAC Pretest BOMAexam questions with 100% correct answers.docx, Exams of Biology

Download HVAC Pretest BOMAexam questions with 100% correct answers.docx and more Exams Biology in PDF only on Docsity! Electric Motors Controls BOMA Pre-Quiz(solved) How does a U.P.S. (Uninterruptible power supply) work? - answer AC rectified to DC batteries then Inverted to AC Batteries energy capacity is measured in? - answer Amp-hours Batteries have two rated values. - answer Voltage and amp-hours How do you top off water in a battery cell? - answer Distilled water when the level is below the plate. A voltage monitor relay is used for? - answer Starting backup generators. Fuel for diesel generators is often stored in a? - answer Day tank _____ converts between electrical and mechanical power. - answer Motor, Generator, alternator. The field winding on a generator: - answer Produces the magnetic field. The stationary members of a generator is called a - answer Stator A motor - answer Converts electrical energy into mechanical energy. an armature is - answer The movable portion of a contractor. In a process control, delay is: - answer The time it takes for a change in the process to be felt. A contactor with two sets of contacts is? - answer 2 pole contactor How do overloads protect a motor? - answer Preventing excessive heating effects of high current A double-break contacts function is to reduce the current of each arc. - answer True Overloads which have a delay in reacting to high current is? - answer To prevent tripping during the starting period What is used when it is necessary to control a high power or high voltage circuit with a low power circuit - answer Replays Time delays on ATS systems can be done by using? - answer Oil dashpots What consists of an electromagnetically inductive coil, wound around a movable steel or iron slug? - answer Solenoid A latching circuit consists of? - answer Start and stop push buttons. The smallest size motor starter is? - answer NEMA rating 00 Providing isolation from hazardous voltages and preventing starting by partial ground faults can be done by using!? - answer Transformers When a remote control is to be needed for an electrical motor, we could use? - answer A latching circuit, 3-wire control, A maintaining circuit In a reversing motor starter we can prevent simultaneous energization of forward and reverse: - answer Using mechanical interlocks Single-phase, split-phase motors can be reversed by? - answer Changing the electrical connections Which are designed to protect motors from drawings too much current? - answer Overloads A sticky armature in a contactor will most likely? - answer Burn out the coil Opening the contacts under load: - answer Causes damage to the contacts A fuses interrupting capacity is based on ? - answer The application it is used in The maximum amperage it can interrupt without being damaged. Manufacturers design What is the circuit interrupt capacity of most fuses? - answer Depends on the application All of the above If a fuse or heater on a three phase power system goes bad? - answer You should replace all three Using a megger to get the winding resistance of a motor winding indicates? - answer The condition of the winding insulation When should you use a VFD? - answer When the motor load fluctuates, When soft start is desirable, When starting large loads during peak hours, All of the above A four-pole induction motor operates with a line frequency of 60 hz. What is the speed at which the field is rotating in revolutions per minute? - answer 1800 The speed of a three phase motors field rotates is? - answer Synchronous speed Torque is? - answer Force times distance A 7200 rpm motor at 60hz has? - answer Two poles What determines the speed of a synchronous motor? - answer Poles Opposite poles of a magnet will? - answer Attract A magnetic field? - answer Is created when current flows, Surround a magnet, Is invisible A temporary magnet is? - answer An electromagnet What is required to create an electromagnet? - answer Wire, Electricity, Coil A magnetic field is created when? - answer Electricity flows If a motors rotors locks? - answer Overloads should open Poor motor ventilation/ clogged vents would likely cause? - answer Motor overheating A defective starter would likely not cause? - answer Damage bearings, excessive vibrations, high voltages, If a motor is running hot? - answer Check the amperage The overload protection protects? - answer The branch circuit, The motor, The branch conductors Reversing a DC motor requires? - answer Reversing the direction of electricity flow. Silicone-controlled rectifies (SCRs)? - answer Are used as DC drives A tachogenerator? - answer Generates a voltage based on speed. At a 60 hz frequency, a two-pole motor will operate at? - answer 3600 rpms A device used to measure the rotating speed of a motor is called a? - answer Tachometer An induction motor will develop maximum torque at what speed? - answer 70% to 80% VFDs control the speed of a motor by? - answer Changing the voltage, Changing the frequency, Changing the input to the motor Low voltage to a motor can cause? - answer Overheating If the motor and starter are installed in locations with different temperature conditions? - answer The heater section will be affected Polyphase means? - answer More than one phase