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As we know, you can mechanically lock a DC brush motor by short the two terminals with relative strength. Now, in my design I wanted to use BLDC for reduced noise, but can I do something similar for the locking? What is the approximate strength.

This has to go bi-direction, so a Ratchet is not possible.

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Yes, you can short the windings of a BLDC motor to brake or "lock" the motor (Though it will not be truly locked). The strength will depend on the torque constant of the motor, and the total resistance between the windings.

Any back-emf from applied shaft torque across the short impedance will result in a winding current, so you can calculate the opposing torque with the torque constant.

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  • \$\begingroup\$ Thank you. Quick follow up: does this has difference regarding Y or Delta connection? The circuit itself will undoubtedly complected right? \$\endgroup\$ – Bogdan Mar 14 '18 at 20:15
  • \$\begingroup\$ No difference between delta or Y connection, similar operation applies. If you are driving the motor with a three-phase FET bridge for example you can turn on all the bottom FETS at the same time for braking. Actually fairly easy. \$\endgroup\$ – John D Mar 14 '18 at 20:43

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