5.2 b: Application146 YASKAWA ELECTRIC SIEP C710616 27C YASKAWA AC Drive A1000 Technical Manual■ b2-12: Short Circuit Brake Time at StartShort Circuit Braking can be used in OLV/PM and AOLV/PM. By shorting all three motor phases, it produces a brakingtorque in the motor and can be used to stop a coasting motor before starting it again.Parameter b2-12 sets the time for Short-Circuit Brake operation at start. Disabled when set to 0.00 s.Note: Short Circuit Braking cannot prevent a PM motor from being rotated by an external force. To prevent the load from rotating themotor, use DC Injection.■ b2-13: Short Circuit Brake Time at StopThe Short Circuit Braking described for parameter b2-12 can also be applied at the end of deceleration in order tocompletely stop high inertia loads. Short Circuit Braking is initiated for the time set in b2-13 when the output frequencyfalls below the higher of the values b1-02 and E1-09. Parameter b2-13 sets the time for Short Circuit Braking at stop.Disabled when set to 0.00 s.■ b2-18: Short Circuit Braking CurrentParameter b2-18 sets the current level for Short Circuit Braking operation as a percentage of the motor rated current.Even though a higher current level can be set using b2-18, the Short Circuit Braking current will not be higher than thedrive rated current (120% for Normal Duty, 150% for Heavy Duty).◆ b3: Speed SearchThe Speed Search function allows the drive to detect the speed of a rotating motor shaft that is driven by external forces(e.g., a fan rotating by windmill effect or motor driven by load inertia). The motor operation can be directly started fromthe speed detected without needing to stop the machine before.Example: When a momentary loss of power occurs, the drive output shuts off. This results in a coasting motor. Whenpower returns, the drive can find the speed of the coasting motor and restart it directly.For PM motors, only parameter b3-01 is needed to enable Speed Search.For induction motors, the drive offers two types of Speed Search than can be selected by parameter b3-24 (SpeedEstimation and Current Detection). Both methods are explained below, then followed by a description of all relevantparameters.■ Current Detection Speed Search (b3-24 = 0)Current Detection Speed Search is for use with IM motors. Current Detection Speed Search detects the motor speed bylooking at motor current. When Speed Search is started it reduces the output frequency starting either from the maximumoutput frequency or the frequency reference while increasing the output voltage using the time set in parameter L2-04.As long as the current is higher than the level set in b3-02, the output frequency is lowered using the time constant b3-03.If the current falls below b3-02, the drive assumes that the output frequency and motor speed are the same andaccelerates or decelerates to the frequency reference.Be aware that sudden acceleration may occur when using this method of Speed Search with relatively light loads.The following time chart illustrates how Current Detection Speed Search operates after a momentary power loss (L2-01must be set to 1 or 2):No. Name Setting Range Defaultb2-12 Short Circuit Brake Time at Start 0.00 to 25.50 s 0.00 sNo. Name Setting Range Defaultb2-13 Short Circuit Brake Time at Stop 0.00 to 25.50 s 0.50 sNo. Name Setting Range Defaultb2-18 Short Circuit Braking Current 0.0 to 200.0% 100.0%
