Document jBVd8NvMqGkrOReKLoN8XBBZy

644 Chapter 35 1945. Guide_____ only or for speed regulating duty. Fig. 12 illustrates recommended control practice for wound rotor motors. Typical specifications, for wound rotor motor control are shown on page 642. Synchronous motor controllers should provide pull-out protection, automatic synchronization or automatic stopping of the motor after pull-out, and insurance of complete starting sequence, as well as overload and low voltage protection. The control may be either magnetic or semi-magnetic at full or reduced voltage. Semi-magnetic starters provide automatic field control but require hand operation for closing the line contactors to'start and transfer to full voltage. In applying reduced voltage starters to synchronous motors it should Table 2. Typical Application Requirements of Synchronous Motor Drives Showing Starting, Pull-In and Pull-Out Torques Method of Motor to Load Starting Conditions Torques Start Pull- Pulling in Out Remarks Fans Exhaust and Ventilating Coupled or Belted Cycloidal Positive Coupled or Engine Type Blowing Engines 1 Reciprocating Engine Type Turbo High Speed Direct Connected or Step Up Gear Air Engine Type Usually Loaded Unloaded 50 60-125 150 40-60 40-60 150 Unloaded 40 40-60 150 Unloaded tlntake Closed) Unloaded 30 40 50 150 40 150 S Ammonia and 8 Ammonia 8 Booster High Speed--Belted Unloaded Low Speed--Engine Type (By By-Pass) Occasionally Coupled 40 40 150 | o Freon High Speed--Belted Low Speed--Engine Unloaded 45 60 150 (By By-Pass) Gas High Speed--Belted Reciprocating Low Speed--Engine Unloaded 40 40 150 (By By-Pass) WK* of Fan Must be Considered Two-Speed Motors Sometimes Used . WF? of Blower Must be Considered Flywheel Effect Important Flywheel Effect Important Flywheel Effect Important Flywheel Effect Important be remembered that, since these motors are started on damper windings and during the acceleration period function similarly to squirrel-cage motors,' the starting torque varies as the square of the applied voltage. Consideration should be given to insure development of sufficient motor torque to accelerate the load. Typical specifications for synchronous motor control are shown on page 645. Multi-Speed control may be either manual or' magnetic, and at full or reduced voltage. When using automatic magnetic control with two-, three-, and four-speed separate winding or consequent pole motors, control may be obtained from a remote point by means of a push button master switch. The various speeds of the motor are obtained from the master switch by simply depressing the correct push button. This is known as selective speed control. It is commonly used in the smaller ~Motors:and-Motor-Controls Typical Specifications for Synchronous Motor Control Synchronous Motor Control for..................................... .. (Application) Motors Shall Provide for j Starting And Shall-Be {L^i^eUc}- Voltage Starting Shall Be Obtained By Means of (Autotransformers ] "Actors And Sha" The KVA Saturable Reactors J Inrush to a Maximum of....... per cent of Full Load KVA.) , The Control Panel Shall Be For {g^ffioard } Assembly And Shall Be of } Con- struction. It Shall Provide Overload, Under Voltage Protection And After Pulling Out of Step 645 Typical Specifications for Single Phase Motor Control Control For Single Phase.......... 1........................................ (Fan, Pump, etc.) Motors Shall Consist of a {Magnetic } TyP0 {Redded Vol'teg'e/ Starter Providing Overload Protection (And Low Voltage); And A Separate Safety Disconnecting Switch. theater installations where the fan and motor are located backstage and the speed control is located in the lobby. Multi-speed motor controllers may be provided with compelling relays which make it necessary for the operator to press the first speed button before regulating the motor to the desired speed. This insures that the motor is always started at low speed before adjusting to one of the higher speeds. Timing relays which provide for automatic acceleration may be used for control. With this feature the motor will always start at low speed and automatically accelerate, to the desired speed. Decelerating relays may be used to reduce the shock effect of the braking action to the motor and drive when the speed is reduced from a higher to a lower speed. Single Phase motor control usually consists only of a linestarter, either