For asynchronous motor

(3.40)

where m – is a set number of starting stages;

R_r = R₂;

R_r – is active component of rotor resistance, Оhm (see the formula 3.32);

R₂ – is a resistance of rotor phase winding of asynchronous motor [Ohm]

R₂ = 0.12 Оhm (it's advisable)

(3.41)

where R_1r – is a full resistance of rotor phase;

U_2r – is a rotor voltage, V (appendix Б);

І_st – is a starting current of the motor, A.

(3.42)

where Кп = 2.5 (it's advisable)

І_2r – is a rated current of a rotor, A (appendix Б)