Danfoss FC 300 Design Manual

Also see for FC 300: Operating instructions Instruction manual Design guide Design guide Design guide

Contents

Danfoss FC 300 Design Manual Manual pdf 200 page image

9.1.8 Advanced Mechanical Brake Control for Hoisting Applications1. The vertical movementIn the vertical movement, the key point is that the load must be held, stopped, controlled (raised, lowered) in a perfectly safe mode during the entireoperation.Because the frequency converter is not a safety device, the crane/lift designer (OEM) must decide on the type and number of safety devices (e.g. speedswitch, emergency brakes etc.) to be used, in order to be able to stop the load in case of emergency or malfunction of the system, according to relevantnational crane/lift regulations.2. Connecting the mechanical brake to the frequency converter- The electromagnetic disc brake works by the action of a set of springs and is released when applying voltage to the brake coil.- This means the motor will brake automatically in case of voltage failure, as a significant safety feature.- Whenever a mechanical brake is present, it is strongly recommended to use an external contactor, to take over switching on/off the brake.- Because of inverse voltage peaks during switch on/off, it is recommended to use a diode block mounted on the contactor’s coil, for protectionof the frequency converter.- The contact 01-02 in the frequency converter stays normally open, so the output is not energized.- When the START condition comes from the command circuit, the drive closes the 01-02 contact according to the programmed brake logic. Theoutput is now energized until STOP condition occurs.- If the frequency converter is in alarm or fault condition, the output relay immediately cuts in.3. The control parametersIn open loop structure, the relevant (active) parameters to controlling the mechanical brake output relay are:- Par. 5-40Function Relay or par. 5-41On Delay, Relay. Mechanical brake control: activates the output brake relay function- Par. 2-20Release Brake Current. When the START condition is present, the motor current is increased to the set value (closed to the nominalmotor current), in order to produce enough torque to hold the load during the brake release.- Par. 2-21Activate Brake Speed [RPM]. By setting this parameter the mechanical brake will be engaged over a rotating shaft. Recommendedvalue is ½ of the slip. If the value is too high, the mechanical system will be exposed to shocks at every stop. If the value is too small, thetorque (current) might be insufficient to holding the load at zero speed. When STOP condition is present, the motor is ramping down to zerospeed (mechanical brake is still open), and at the set value (rpm) engages (closes down) the mechanical brake.- Par. 2-22Activate Brake Speed [Hz]. Linked to par. 2-21Activate Brake Speed [RPM]. Automatically adjusted according to the par. 2-21 value.9 Application Examples FC 300 Design Guide200 MG.33.BC.02 - VLT® is a registered Danfoss trademark9