SJ300 Inverter
The External Brake Control function enables the inverter to control external electromechanical brake systems with a particular safety characteristic. For example, elevator control systems maintain the brake on the load until the drive motor has reached a releasing frequency (point at which the external mechanical brake is released). This ensures that the load does not have an opportunity to begin coasting before the inverter begins driving the motor. The External Brake Control function can be enabled by setting parameter B120=01. The diagram below shows the signals that are important to this function.
Inverter |
| [BRK] Brake release | External Brake | |||
|
|
|
|
| ||
|
| [BOK] Brake confirmation | System | |||
|
|
|
|
|
|
|
|
| [BER] Brake error |
|
|
|
|
|
|
|
|
| ||
|
|
|
| Emergency Brake | ||
|
|
|
|
|
| (or alarm, etc.) |
|
|
|
|
|
|
|
The steps below describe the timing diagram of events on the following page.
1.When the Run command turns ON, the inverter begins to operate and accelerate to releasing frequency (B125).
2.After the output frequency arrives at the set releasing frequency (B125), the inverter waits for the brake release confirmation, set by B121. The inverter outputs the braking release signal [BRK]. However, if the output current of the inverter is less than the releasing current set by B126, the inverter does not turn ON the brake release output [BRK]. The lack of the proper current level indicates a fault (such as open wire to motor). In this case, the inverter trips and outputs the braking error signal [BER]. This signal is useful to engage an emergency brake to ensure the load does not move, if the primary braking system has failed.
3.While the brake release output [BRK] is ON, the inverter drives the motor but does not accelerate immediately. The inverter waits for confirmation from the external brake. When the external brake system properly releases, it signals the inverter by using the Brake OK input terminal [BOK]. If [BOK] is not assigned to an intelligent input, B124 is ignored.
4.When the brake operates properly and signals with the [BOK] input, the inverter waits for the required time for acceleration (B122), and then begins to accelerate to the set target frequency. If [BOK] is not assigned to an intelligent input, acceleration begins after the delay time set by B122 after [BRK] signal occurs.
5.When the Run command turns OFF, the procedure outlined above happens in reverse. The idea is to engage the brake before the motor comes completely to a stop. The inverter decel- erates to the releasing frequency (B125) and turns the brake release output [BRK] OFF to engage the brake.
6.The inverter does not decelerate further during just the waiting time for brake confirmation (B121). If the brake confirmation signal does not turn OFF within the waiting time for brake confirmation, the inverter causes a trip alarm and outputs the brake error signal [BER] (useful for engaging an emergency brake system).
7.Normally, the brake confirmation signal [BOK] turns OFF, and the inverter waits the required waiting time. Then the inverter begins to decelerate again and brings motor and load to a complete stop (see timing diagram on next page).
Code | Function | Data or Range | Description |
|
|
|
|
|
|
|
|
B120 | Brake control | 00=Disable | Enables external brake control function within the |
| enable | 01=Enable | inverter |
|
|
|
|
B121 | Brake waiting | 0.00 to 5.00 sec. | Sets the time delay after arrival at release |
| time for release |
| frequency (B125) before the inverter outputs brake |
|
|
| release signal [BRK] |
|
|
|
|
B122 | Brake wait time | 0.00 to 5.00 sec. | Sets time delay after brake confirmation signal |
| for acceleration |
| [BOK] is received until the inverter begins to accel- |
|
|
| erate to the set frequency |
|
|
|
|
Operations Monitoring and