The electromagnetic double‑disc spring‑operated brake KFB, see picture "KFB spring‑operated brake with manual lever", is intended to operate solely as a holding brake for this application. With the exception of emergency braking, it may only be operated as a dynamically loaded operational brake if it is appropriately dimensioned or after consultation with the manufacturer. It is a spring‑loaded, electrically operated, double‑disc brake, which operates when the power is switched off. When the coil (2) is energized with a DC voltage, the brake is released electromagnetically. If the coil (2) is de‑energized, the springs (6) press the armature plate (4) axially against the friction‑lining carrier (5) which in turn presses against the brake flange (7); this sequence provides the braking action. The brake is released when the coil (2) is energized. The magnetic field attracts the armature plate (4) towards the coil form (1), counteracting the spring pressure on the coil form. The air gap can be adjusted within a wide range, ensuring high availability of the brake. The motor and brake are coupled by means of a flange (12). Emergency brake release is possible by means of 2 emergency release screws – optionally with hand lever release.
As a result of the compact design with the enclosed coil form housing and appropriate sealing from the shaft, the brake has degree of protection IP67 when the housing is closed.
All the brake connections such as coil, microswitch, etc. are taken to the motor terminal box.
KFB spring‑operated brake with manual lever
The brakes should be connected at the DC end, i.e. between the rectifier and coil (see circuit diagram below). This ensures a significantly shorter closing time than if the brake were connected at the AC end. A protective element (varistor + spark quenching) must be fitted in parallel to each brake coil. This protects the brake coil against excessively high de‑energization voltages on the one hand, and the contactor contacts on the other. These protective elements must be installed close to the brake coils where possible, e.g. in the motor terminal box or in a distribution board on the subframes in the case of traversing gear. Protective elements PE‑400/150/5 are directly available from the manufacturer1) under Article No. 008099300249.
Connection voltage, max.
400 V DC
Max. coil current
Max. energy absorption of one trip
Max. continuous output (average) of energy absorption
Trip peak at max. coil current
< 450 V
-40 ... +50 °C
Permissible cross section of connecting lead
0.2 ... 2.5 mm2
Degree of protection
Emergency release with hand lever, option J25
In addition to brake release at zero current via 2 emergency release screws, it is also possible to release the brake by means of a hand lever permanently mounted on the brake housing. The lever is lockable.
Microswitch for "brake released" monitoring, option J26
The brake can be fitted with a microswitch for monitoring the "brake released" state. The contact is rated for:
Microswitch for air gap monitoring/wear, option J24
A 2nd microswitch can be fitted to monitor the "maximum air gap" function. Tripping of this contact indicates that full braking power is no longer available and the air gap must be adjusted immediately. The contact load rating is identical to that of the "brake released" microswitch.
Standstill heater, option J27
The installation of a heater can prevent the formation of condensate, e.g. caused by fluctuations in temperature and air humidity, inside the brake. This heater must not be switched on when the motor is operating. The heater is designed for a supply voltage of 230 V AC and a heat output of 40 W.
Encoder mounting, option J28/J29
An encoder (e.g. POG 10) can be mounted on the brake. Additional mounting components and other measures are required on the brake to fit an encoder.
Tacho socket T2 with coupling and mounting components is ordered with option J28(see section "Design").
If an encoder is to be fitted at a later date, the brake can be supplied prepared for encoder mounting. This is possible with option J29. Option J29 does not include the coupling and mounting components.
It is also possible to retrofit an encoder by replacing the brake housing (the parts required, such as new housing, coupling, etc., can be ordered directly from the manufacturer1)) using the brake serial number as a reference).
Brake control unit BCU
A brake control unit (BCU) can also be used to supply and monitor the brake on single drives. For technical data, price, etc., please contact the manufacturer1) directly.
Rectifier in terminal box, option C07/C01
The brake motors can also be supplied with a bridge rectifier installed.
It must, however, be noted that the closing time for the brake can be a factor of 10 longer than the values specified in the tables (see section "Technical specifications" below) because it is connected at the AC current side.
Three‑phase asynchronous motors 1LP4, 1LP6, 60 Hz variant·
The motor types 1LP4 and 1LP6 are also available in a 60 Hz variant.
The following must be stated in addition to the Article No.:
Technical data on request.
Pintsch Bamag GmbH
The following dimensioning parameters must be taken into account when a brake is selected:
On the assumption that the deceleration rate must be approximately equal to the acceleration rate, the braking torque should be calculated as follows:
MBR = MJa × η2
Braking torque of the mechanical brake
Accelerating torque for accelerating linear-motion and rotating masses
Accordingly, the braking torque of the mechanical brake must be approximately equal to the required maximum motor torque.
The braking energy for occasional emergency trips must be checked to ensure that it does not cause the brake to overheat. Please refer to table in section "Technical specifications" for permissible values. The braking energy produced for traversing gear can be calculated approximately with the following equation:
Energy capability/braking energy in kJ
Existing braking torque in Nm
Total of all load torques in Nm referred to the brake (motor) shaft
Speed of brake (motor) shaft in rpm
Total moment of inertia to be braked in kgm2 reduced to the brake (motor) shaft
is positive if it supports braking (e.g. hoisting a load)
is negative if it counteracts braking (e.g. lowering a load)
The total moment of inertia Itot is the sum of the individual moments of inertia of the plant components to be braked, reduced to the brake (motor) shaft, and the moment of inertia of the linear-motion masses. The equivalent mass inertia IEqv of a linear-motion mass m with velocity v, referred to the brake (motor) speed nBr, is calculated as follows:
Mass of the linear-motion load in kg
Velocity of the linear-motion load in m/s
Speed of brake (motor) shaft in rpm
The velocity and/or speed to be entered here must equal the maximum values in normal operation. An increase in velocity resulting from wind forces may also need to be taken into account.
The brake must be capable of absorbing the heat produced by the occasional emergency braking operation. The maximum permissible energy capability Q is shown in the diagram below as a function of the number of switching operations.
The permissible energy capability Q for a single emergency trip can be found in the table in section "Technical specifications".
Energy capability Q, braking speed n = 1500 rpm
KFB spring-operated brakes
Rated voltage 1)
Moment of inertia
Energy capability Q
Energy capability Q
Closing time t12)
Release time t22)
1) Rated voltage according to DIN IEC 38 with tolerances of +6 % and -10 % according to DIN VDE 0580.
2) Switching time terms defined according to DIN VDE 0580, Closing time t1 = Connection time t1, Release time t2 = Disconnection time t2
Energy capability per braking operation [kJ per switching operation]
Braking operations per hour [1/h]
Closing time: Time from power OFF until 90 % of rated braking torque is reached
Release time: Time from power ON until 10 % of rated braking torque is reached
Measured at 20 °C
The normal version of the brake is supplied for a coil voltage of 207 V DC. Voltages of 110 V DC and 180 V DC are also available at no extra cost (please state in plain text in the order). Other coil voltages on request.