Safe Disable Circuit

The Safe Disable circuit has two isolated channels (terminals H1 and H2) that stop the output transistors. The input can use the internal power supply of the drive.

Set the EDM function to one of the MFDO terminals [H2-xx = 21 or 121] to monitor the status of the Safe Disable function. This is the “Safe Disable monitor output function”.

Figure 1. Safe Disable Function Wiring Example

Connect Safe Disable Input Contacts to Multiple Drives

To Use the Drive Internal Power Supply

Figure 2 shows an example of how to connect Safe Disable contacts.

From the terminals HC-SN of drive 1, supply the power for the Safe Disable function for the applicable drives. These conditions limit the number of units to connect:

  • Internal power supply capacity

  • Number of MFDIs used

  • Supply current to the external sensors

Figure 2. Connection Example to Use the Internal Power Supply

To Use 24 V External Power Supply

Figure 3 shows an example of how to connect Safe Disable contacts. These conditions limit the number of units to connect:

  • External power supply capacity

  • Number of MFDIs used

  • Supply current to the external sensors

Figure 3. Connection Example to Use 24 V External Power Supply

Number of Possible Drives to Connect

 

Power Supply

Digital Inputs

24 V Output

Number of Drives

Internal power supply

(Drive 1)

Yes

(7-channel input)

Yes 1

1

No

13

No

Yes 1

4

No

17

External power supply

-

Different for different external power supply capacities 2
 

Use this formula to calculate the number of units to connect:

  • n: Number of units to connect

  • Iomax: Maximum current that the power supply can supply (234 mA for the internal power supply)

  • IMFDI: Current consumed per MFDI (6 mA)

  • nMFDI: Maximum number of MFDIs that can be activated at the same time (maximum of 7-channel)

  • Isensor: Current externally supplied for sensor power supply (maximum of 150 mA)

  • Isafety: Current consumed by Safe Disable terminals H1 and H2 (12 mA)

Note:

Round the values to the first decimal place.

Enabling and Disabling the Drive Output (“Safe Torque Off”)

Refer to Figure 4 for an example of drive operation when the drive changes from “Safe Torque Off” status to usual operation.

Figure 4. Safe Disable Operation

Switching from Usual Operation to “Safe Torque Off”

Turn OFF (open) safety input terminal H1 or H2 to enable the Safe Disable function. When the Safe Disable function is enabled while the motor is operating, the drive output and motor torque turn off and the motor always coasts to stop. The b1-03 [Stopping Method Selection] setting does not have an effect on the stopping method.

The “Safe Torque Off” status is only possible with the Safe Disable function. Clear the Run command to stop the drive. Turning off drive output (a baseblock condition) ≠ “Safe Torque Off”.

Note:

  • When it is necessary to ramp to stop the motor, do not turn off terminals H1 and H2 until the motor fully stops. This will prevent the motor from coasting to stop during usual operation.

  • A maximum of 3 ms will elapse from when terminals H1 or H2 shut off until the drive switches to the “Safe Torque Off” status. Set the OFF status for terminals H1 and H2 to hold for at least 3 ms. The drive may not be able to switch to the “Safe Torque Off” status if terminals H1 and H2 are only open for less than 3 ms.

Going from “Safe Torque Off” to Usual Operation

The safety input will only release when there is no Run command.

  • During Stop

    When the Safe Disable function is triggered during stop, close the circuit between terminals H1-HC and H2-HC to disable “Safe Torque Off”. Enter the Run command after the drive stops correctly.

  • During Run

    If you trigger the Safe Disable function during run, clear the Run command, then close the circuit between terminals H1-HC and H2-HC to disable “Safe Torque Off”. Enter the Stop command, then enter the Run command when terminals H1 and H2 are activated.

Safe Disable Monitor Output Function and Keypad Display

Refer to Table 1 for information about the relation between the input channel status, Safety monitor output status, and drive output status.

Table 1. Safe Disable Input and External Device Monitor (EDM) Terminal Status

Input Channel Status

Safety Monitor Output Status

Drive Output Status

Keypad Display

READY LED

MEMOBUS Register

0020H

Input 1

(H1-HC)

Input 2

(H2-HC)

MFDO Terminal

(H2-xx = 21)

MFDO Terminal

(H2-xx = 121)

bit C

bit D

ON

(Close the circuit)

ON

(Close the circuit)

OFF

ON

Baseblock

(Drive ready)

Normally displayed

READY: Illuminated

0

0

OFF

(Open)

ON

(Close the circuit)

OFF

ON

Safety status

(STo)

SToF

(Flashing)

ALM/ERR: Flashing

1

0

ON

(Close the circuit)

OFF

(Open)

OFF

ON

Safety status

(STo)

SToF

(Flashing)

ALM/ERR: Flashing

1

0

OFF

(Open)

OFF

(Open)

ON

OFF

Safety status

(STo)

STo

(Flashing)

READY: Flashing

0

1

Safety Function Status Monitor

The drive Safety monitor output sends a feedback signal about the status of the Safety function. The Safety monitor output is one of the possible settings available for the MFDO terminals. If there is damage to the Safe Disable circuit, a controller (PLC or safety relay) must read this signal as an input signal to hold the “Safe Torque Off” status. This will help verify the condition of the safety circuit. Refer to the manual for the safety device for more information about the Safety function.

It is possible to switch polarity of the Safety monitor output signal with the MFDO function settings. Refer to Table 1 for setting instructions.

Keypad Display

If the two input channels are OFF (Open), the keypad will flash STo [Safe Torque OFF].

If there is damage to the Safe disable circuit or the drive, the keypad will flash SToF [Safe Torque OFF Hardware] when one input channel is OFF (Open), and the other is ON (Short circuit). When you use the Safe disable circuit correctly, the keypad will not show SToF.

If there is damage to the drive, the keypad will show SCF [Safety Circuit Fault] when the drive detects a fault in the Safe disable circuit. Refer to the chapter on Troubleshooting for more information.

Validating the Safe Disable Function

After you replace parts or do maintenance on the drive, complete all necessary wiring to start the drive, then follow these steps to test the Safe Disable input. Keep a record of the test results.

  1. When the two input channels are OFF (Open), make sure that the keypad flashes STo [Safe Torque OFF], and make sure that the motor is not running.

  2. Monitor the ON/OFF status of the input channels and make sure that MFDO set to the EDM function operates as shown in Table 1.

    If one or more of the these items are true, the ON/OFF status of the MFDO may not display correctly on the keypad.

    • Incorrect parameter settings.

    • A problem with an external device.

    • The external wiring has a short circuit or is disconnected.

    • There is damage to the device.

    Find the cause and repair the problem to correctly display the status.

  3. Make sure that the EDM signal operates during usual operation as shown in Table 1.

1

This is when you use a maximum of 150 mA.

2

24 V, 12 mA is necessary for each drive.