Parameter P1237 is used to set the start/stop cycle for dynamic braking, and it's expressed as a percentage. You're asking whether this percentage refers to the DC bus voltage of the inverter. For example, if you set it to 20% and the normal DC bus voltage is 580V, does that mean the brake unit activates when the voltage reaches 696V (which is 20% higher)? And once the voltage drops below 696V, does it automatically turn off?
Shaanxi Xinlong Metal Electro-mechanical Co., Ltd. , https://www.cnxlalloys.com
Answer: 1. P1237 defines the duty cycle or the ratio of active time to stop time for the dynamic braking resistor, not the ON level of the DC bus voltage. When the DC bus voltage exceeds the dynamic brake’s activation threshold, the brake is engaged immediately after the cycle expires.
2. Your understanding of the "power brake turn-on level" is close, but there are more details to consider. If parameter P1254 (automatic detection of the DC voltage loop ON level) is set to 0, the brake unit activates when the DC voltage reaches 1.13 × 1.414 × P210 (which is based on the supply voltage). However, if P1254 is set to 1, the activation voltage is calculated as 0.98 × r1242. This means the brake unit will activate at different voltage thresholds depending on the configuration. It's important to check these settings carefully to ensure proper operation and avoid unnecessary wear on the braking components.