Normally a motor can be locked by shorting its phases.
When the motor is not connected and we short all the the three phase terminals (tie them together) and try to rotate the shaft it offers lot of opposition.
Why is this the case?
Electrical Engineering Stack Exchange is a question and answer site for electronics and electrical engineering professionals, students, and enthusiasts. It only takes a minute to sign up.Sign up to join this community
Shorting the phases is creating a low resistance load which makes the motor work hard. This is the braking opposition you notice.