8.1 Selection instructions for brake resistors

The SK300 series VFD with a power output of 22KW or less all provides a built-in brake unit. Users can choose different braking resistance values and power according to their actual situation, but the resistance value cannot be less than the recommended value in the table. The braking resistance power can be selected larger. The selection of braking resistor needs to be determined based on the power generated by the motor in the actual application system, which is related to system inertia, deceleration time, load energy, etc. Users should choose according to their actual situation. The larger the system inertia, the shorter the required deceleration time, and the more frequent the braking, the greater the power and lower the resistance value that the braking resistor needs to choose.

VFD mode	Power braking resistor	resistance value for braking resistor	brake unit
SK300-3T-0R7G	150W	≥300Ω	Standard built-in
SK300-3T-1R5G	150W	≥220Ω	Standard built-in
SK300-3T-2R2G	250W	≥200Ω	Standard built-in
SK300-3T-4R0G	300W	≥130Ω	Standard built-in
SK300-3T-5R5G	400W	≥90Ω	Standard built-in
SK300-3T-7R5G	500W	≥65Ω	Standard built-in
SK300-3T-011G	800W	≥43Ω	Standard built-in
SK300-3T-015G	1000W	≥32Ω	Standard built-in
SK300-3T-018G	1300W	≥25Ω	Standard built-in
SK300-3T-022G	1500W	≥22Ω	Standard built-in
SK300-3T-030G	2500W	≥16Ω	Built in optional
SK300-3T-037G	3.7KW	≥12.6Ω	Built in optional
SK300-3T-045G	4.5KW	≥9.4Ω	External
SK300-3T-055G	5.5KW	≥9.4Ω	External
SK300-3T-075G	7.5KW	≥6.3Ω	External
SK300-3T-090G	4.5KW*2	≥9.4Ω*2	External
SK300-3T-110G	5.5KW*2	≥9.4Ω*2	External
SK300-3T-132G	6.5KW*2	≥6.3Ω*2	External
SK300-3T-160G	16KW	≥6.3Ω*2	External
SK300-3T-185G	20KW	≥2.5Ω	External
SK300-3T-200G	20KW	≥2.5Ω	External
SK300-3T-220G	22KW	≥2.5Ω	External
SK300-3T-250G	12.5KW*2	≥2.5Ω*2	External
SK300-3T-280G	14KW*2	≥2.5Ω*2	External
SK300-3T-315G	16KW*2	≥2.5Ω*2	External
SK300-3T-355G	17KW*2	≥2.5Ω*2	External
SK300-3T-400G	14KW*3	≥2.5Ω*3	External

Appendix A ModBus Communication Protocol

1 Overview

The SK300 series VFD provides RS485 serial communication port that adopts MODBUS protocol. Users can achieve centralized control through computers or PLC, set operating commands , modify or read function code parameters, read the working status and fault data of SK300 VFD. And it can serve as a master, facilitating users to synchronize the operation of multiple frequency converters.。

2 Serial Port Data Format

Users can set parameters through the communication function group parameters.

Local address: can be set to 1-247 (cannot conflict with other devices in the communication network), when adress station = O, it is the broadcast address

Communication baud rate: can be selected as 4800, 9600, 19200, or 38400bps.

Communication format: can be selected as 1+8+1 without verification;

Even check 1+8+1+1;

Odd check 1+8+1+1;

Master slave communication method: we can choice master or slave.