BRAKE AND GEAR MOTOR TYPES BASIC INFORMATION AND TUTORIALS

Brake motors are motors equipped with electrically controlled brakes as an integral part of the motor assembly. The brake motor manufactured by one company consists of one or more rotating steel disks splined on a pinion on the motor shaft, with stationary friction linings on each side of each disk.

A helical spring in the center applies pressure to provide the required braking, and two, three, or four magnets, depending on the rating of the brake, supply force to compress the spring and release the brake while the motor is running.

When power is applied to the motor, the brake is immediately energized, since the brake leads are connected directly to the motor leads in the conduit box. The current energizes the magnets, which pull the armature plate toward the end plate.

This action removes the pressure on the revolving disks and allows them to move freely between the friction linings, releasing the brake. Since the rotating disks are separated from the friction surfaces at all times except during actual braking, the motor delivers full rated horsepower at the output shaft.

When the motor is disconnected from the power supply, the magnets are immediately deenergized, and the spring pushes the armature plate away from the adjustable plate toward the motor. This applies braking pressure on the surfaces between the revolving disks and the friction linings, bringing the motor to a quick, smooth stop.

This inherent smooth action, free from hammer blow, keeps stresses at the minimum in the brake and in belts, cables, gears, or chains through which the motor drives.

Gear motors are motors equipped with a built-in reduction gear as an integral part of the motor assembly. The motor itself is generally a 60-Hz, nominal 1750-rpm machine. Output-shaft speeds between 4 and 1430 rpm are available. These motors can be obtained equipped with almost any type of general-purpose polyphase induction, singlephase, or dc motor.

Loads of the same horsepower and speed rating will require different gear sizes, depending upon the type of load. Therefore, time of operation and frequency and severity of shock must be determined to select the proper gear motor for a specific application.

To assist engineers in their selection, the American Gear Manufacturers Association (AGMA) has defined three classes of service, according to the degree to which all these variables are present:

Class I. Steady loads not exceeding the normal rating of the motor on 8-h-per-day service or moderate shock loads if service is intermittent.

Class II. Steady loads not exceeding the normal rating of the motor on 24-h-per-day service or moderate shock loads running 8 h per day.

Class III. Moderate shock loads on 24-h-per-day service or heavy shock loads running 8 h per day.