Difference between revisions of "Safe torque off"
From Granite Devices Knowledge Wiki
| [checked revision] | [checked revision] |
| (4 intermediate revisions by the same user not shown) | |||
| Line 1: | Line 1: | ||
[[File:sto.jpg|thumb|Motor velocity decaying to zero after STO has been activated.]] | [[File:sto.jpg|thumb|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 [https://en.wikipedia.org/wiki/Redundancy_(engineering) redundancy] a way that guarantees the | + | 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 [https://en.wikipedia.org/wiki/Redundancy_(engineering) redundancy] a way that guarantees the removal of torque even in the case of single failure of any component of the system. |
==Usefulness== | ==Usefulness== | ||
Built-in STO in drive provides following | Built-in STO in drive provides following | ||
| Line 9: | Line 9: | ||
*Simplify wiring | *Simplify wiring | ||
;Cons | ;Cons | ||
| − | *Most STO implementations not safe with brush DC motors and also may cause AC motor to lock-up in certain magnetic pole angle | + | *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== | ==STO in Argon servo drive== | ||
[[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: | [[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: | ||
| Line 16: | Line 16: | ||
*Activating dynamic braking of motor | *Activating dynamic braking of motor | ||
*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. | ||
| + | ==STO in IONI servo/stepper drive== | ||
| + | [[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. | ||
| + | |||
[[Category:Technology]] | [[Category:Technology]] | ||
[[Category:Glossary]] | [[Category:Glossary]] | ||
| − | [[Category:Argon]] | + | [[Category:Argon features]] |
| + | [[category:IONI features]] | ||
Latest revision as of 12:01, 13 March 2015
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.
