Configuring Direction-Dependent Interlocks (EBVG1 and EBVG2) for CEMAT Bi-Directional Drive C_DRV_2D

In SIMATIC PCS 7 CEMAT, the bi-directional motor drive block C_DRV_2D features separate operational interlocks for each direction: EBVG1 for Direction 1 and EBVG2 for Direction 2. If an interlock condition applies to both directions, connect the output of a single C_INTERL block to both EBVG1 and EBVG2 simultaneously. If directional protection differs (such as direction-specific end limit switches or forward-only chute level transmitters), instantiate two separate C_INTERL blocks, connecting the first to EBVG1 and the second to EBVG2.

CEMAT Bi-Directional Drive Interlock Philosophy

In industrial plants governed by the CEMAT Minerals library (cement, mining, bulk materials handling), equipment such as reversible belt conveyors, shuttle conveyors, traverse car drives, and two-way rotary valves require bi-directional control. In CEMAT V8.0, V8.1, and V8.2, this functionality is provided by function block C_DRV_2D.

Unlike unidirectional drives (C_DRV_1D), which have single interlock pins (EBVG for operational interlocks and EEVG for essential protection interlocks), C_DRV_2D isolates the interlocking logic for each direction of travel. This allows a conveyor to be locked out from moving forward (due to a full discharge hopper) while remaining fully operational in the reverse direction.

Single vs Separate Interlock Blocks: EBVG1, EBVG2, EEVG1, and EEVG2

When engineering interlocks for C_DRV_2D, the design depends on whether the interlock condition is common or directional:

Common Interlocks (Both Directions Locked): Faults such as motor winding high temperature, emergency pull-cord switches, local isolator open, or main contactor failure require stopping the drive immediately regardless of direction. Here, a single interlock block (C_INTERL or APL Intlk04 / Intlk08) evaluates all general trip conditions, and its output is connected to both EBVG1 and EBVG2 (or EEVG1 and EEVG2).
Direction-Specific Interlocks: Conditions such as 'Forward Over-Travel Limit Switch' or 'Chute Level High East' must only inhibit Direction 1. A separate C_INTERL instance is assigned to Direction 1 (EBVG1), while a distinct C_INTERL instance monitors Direction 2 conditions (EBVG2).
Combining Common and Directional Interlocks: If both common and directional trips exist, feed common interlocks into the first inputs of two separate C_INTERL blocks, with the remaining inputs reserved for direction-specific trips.

C_INTERL Configuration and Signal Interconnection in CFC

To interconnect interlocks with C_DRV_2D in Continuous Function Chart (CFC):

Place Interlock Blocks: In the CFC chart hosting C_DRV_2D, place two C_INTERL blocks. Rename them meaningfully, such as M101_IL_D1 and M101_IL_D2.
Connect Digital Signals: Wire directional permissives into inputs I1 through I5 of the respective C_INTERL blocks. Ensure inverted signals (normally closed field contacts) are correctly parameterized using inversion attributes.
Wire Block Outputs: Interconnect M101_IL_D1.OUT to C_DRV_2D.EBVG1. Interconnect M101_IL_D2.OUT to C_DRV_2D.EBVG2.
Essential Interlocks: For emergency trips that must operate even in manual or local mode, connect failsafe interlocks to EEVG1 and EEVG2.
Compile and Download: Perform a CFC delta compilation and download to the AS.

Faceplate Interlock Diagnostics and Visualization Behavior

In WinCC Runtime, CEMAT faceplates provide dedicated visual diagnostic windows for each direction:

When the operator opens @PG_C_DRV_2D.PDL, the standard view displays separate start/stop commands and status icons for Direction 1 and Direction 2.
If EBVG1 is false (0), the Direction 1 start button is greyed out and the operational interlock indicator displays yellow.
Clicking the Interlock button on the faceplate navigates to the detailed interlock screen (@PG_C_DRV_2D_INTERL.PDL). If separate C_INTERL blocks are linked, the faceplate dynamically switches between Direction 1 and Direction 2 tabs, allowing the operator to pinpoint precisely which sensor is blocking travel.

CEMAT Drive Interlock Pin Assignment Matrix

The following table summarizes interlock pin assignments and operational behaviors on C_DRV_2D:

Pin NameParameter DescriptionDirection AffectedOperational Mode ActiveDrive Response on LossEBVG1Operational Interlock Direction 1Direction 1 OnlyAutomatic and ManualInhibits start; stops drive if running D1EBVG2Operational Interlock Direction 2Direction 2 OnlyAutomatic and ManualInhibits start; stops drive if running D2EEVG1Essential Interlock Direction 1Direction 1 OnlyAll Modes (Auto, Man, Local)Immediate trip of Direction 1EEVG2Essential Interlock Direction 2Direction 2 OnlyAll Modes (Auto, Man, Local)Immediate trip of Direction 2ESVGProtection Interlock (Common)Both DirectionsAll ModesImmediate trip and lockout of drive

Verification

Verify the bi-directional interlocking configuration using the following test sequence:

In CFC online test mode, verify that both EBVG1 and EBVG2 are 1 (healthy).
Start the drive in Direction 1. Confirm motor run feedback ERM1 is healthy.
Simulate a Direction 1 trip by clearing an input on M101_IL_D1. Verify that EBVG1 drops to 0, C_DRV_2D drops COMMAND1, and the motor stops.
While EBVG1 remains 0, attempt to start Direction 2 from the WinCC faceplate. Verify that Direction 2 starts successfully, confirming independence of EBVG2.
Simulate a common emergency trip on ESVG. Confirm that running in either direction trips immediately.

Limitations and Operational Precautions

Consider these operational rules when configuring bi-directional drives:

Mechanical Direction Reversal Delays: Ensure the changeover delay parameter (C_DRV_2D.TUMT) is properly tuned. If a motor is reversed while still coasting, severe mechanical gearbox shock and electrical overcurrent will occur.
Simultaneous Output Interlocking: Never rely solely on software to prevent simultaneous energization of both direction contactors; electrical contactor cross-interlocking (mechanical interlock plus NC contact auxiliary interlock) is mandatory.
Signal Status Quality: If using APL interlocks instead of CEMAT native C_INTERL, verify that signal statuses are properly adapted so bad quality (16#00) translates into a safe logical trip.

Engineer FAQ

How does CEMAT prevent instantaneous reversal between Direction 1 and Direction 2?

The C_DRV_2D block enforces a parameterized changeover dead-time timer (TUMT). The motor must come to a complete standstill before the reverse contactor output is permitted to energize.

What is the maximum number of inputs on C_INTERL?

C_INTERL typically supports 5 digital inputs (I1 to I5). If more inputs are required, multiple C_INTERL blocks can be cascaded, or an APL Intlk08 / Intlk16 block can be used.

Can I bypass an operational interlock from the CEMAT faceplate?

If configured and permitted by user authorization, an operator can apply a temporary software interlock bypass directly from the CEMAT diagnostic faceplate.