Difference between revisions of "Safe torque off"

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*Software (firmware) disabling motor control
 
*Software (firmware) disabling motor control
 
The cutting of AC power makes Argon safe even with DC motor and does not allow AC motor lock up.
 
The cutting of AC power makes Argon safe even with DC motor and does not allow AC motor lock up.
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==STO in IONI servo/stepper drive==
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[[IONI Servo & Stepper Drive]] has one dedicated digital input for STO. When STO2 line is logic low, drive's power stage control is de-energized making it unable to drive any current or voltage to motor coils. In addition to this, drive firmware reads STO2 status and disables motor control signals.
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[[Category:Technology]]
 
[[Category:Technology]]
 
[[Category:Glossary]]
 
[[Category:Glossary]]
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[[Category:Argon features]]
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[[category:IONI features]]

Latest revision as of 12:01, 13 March 2015

Motor velocity decaying to zero after STO has been activated.

Safe torque off a.k.a. STO is a motor drive function that disables drive's ability to produce torque with motor and also prevents unintentional motor start-up. STO is built with redundancy a way that guarantees the removal of torque even in the case of single failure of any component of the system.

Usefulness[edit | edit source]

Built-in STO in drive provides following

Pros
  • Eliminate the need of power cutting relay or contactor
  • Can provide dynamic braking of motor under STO condition instead of letting motor free-wheel which usually increases safety
  • Reduce cost of safety circuity
  • Simplify wiring
Cons
  • Most STO implementations not safe with brush DC motors and also may cause AC motor to lock-up in certain magnetic pole angle (thus motor can still produce torque but cannot rotate more than 1/2 revolutions)

STO in Argon servo drive[edit | edit source]

Argon (servo drive) has 4-way STO function making it one of the most fail safe implementations available. Safety is being provided by four simultaneous actions:

  • Removing AC input power from power stage by the means of internal safety rated relay
  • Cutting gate drive voltage from power stage rendering power stage inactive
  • Activating dynamic braking of motor
  • Software (firmware) disabling motor control

The cutting of AC power makes Argon safe even with DC motor and does not allow AC motor lock up.

STO in IONI servo/stepper drive[edit | edit source]

IONI Servo & Stepper Drive has one dedicated digital input for STO. When STO2 line is logic low, drive's power stage control is de-energized making it unable to drive any current or voltage to motor coils. In addition to this, drive firmware reads STO2 status and disables motor control signals.