Lenze Gearmotor Product Warning (Verification of Ground Connectivity)

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Mark Norris
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Issued by Responsible Phone / Email Date DCUS/ETC-MT Paul Zielbauer 269-697-5300 12/19/11 paul.zielbauer@boschrexroth-us.

1 Issued by Responsible Phone / Date DCUS/ETC-MT Paul Zielbauer /19/11 paul.zielbauer@boschrexroth-us.com Material and information flow technology Lenze Gearmotor Product Warning (Verification of Ground Connectivity) Overview PB-M07-11 Bosch Rexroth recently encountered in its factory an isolated problem with certain gearmotors supplied by Lenze. Although after investigation, no additional gearmotors were found to have this problem, Bosch Rexroth wants to provide notification with respect to Lenze gearmotors already in operation. This document describes two methods of checking the ground wiring of Lenze gearmotors in the field. If the gearmotors do not pass this first-level verification, or if additional testing is desired, then the full IEC compliant testing using a continuity tester that meets the specifications of DIN standard EN (supplying at least 10A for 3 seconds) should be followed. Additional documentation about that testing method is available from Bosch Rexroth. NOTE: These procedures should ONLY be performed by properly authorized personnel, fully trained and certified for electrical maintenance work. LOCK OUT AND TAG OUT ALL POWER SOURCES ACCORDING TO YOUR FACILITY S LOTO PROCEDURES BEFORE CHECKING THE LENZE GEARMOTORS. Description of the Problem The Lenze Gearmotors supplied by Bosch Rexroth use a nine-post terminal block with three posts for the incoming three-phase power, three posts for the motor winding leads, two posts for the internal thermal switch, and a ground (PE) post. The ground post is connected to the gearmotor ground lug on the motor frame with a short wire jumper. Bosch Rexroth discovered two gearmotors where the ground jumper had the ring terminal crimped on without having been properly stripped of insulation (See Figure 1 below). This would prevent connectivity and leave the gearmotor not properly grounded. Figure 1: Unstripped Ground Jumper 1

Checking Units in the Field In the field, the first-level method of verifying that there is proper continuity through the ground jumper is to remove power and check visually and with a reliable

2 Checking Units in the Field In the field, the first-level method of verifying that there is proper continuity through the ground jumper is to remove power and check visually and with a reliable multimeter. The following sections describe this in detail. If there are any indications that the ground jumper is not properly stripped and connected, or if additional verification is required, a full connectivity test with a tester that meets DIN standard EN should be performed. NOTE: These procedures should ONLY be performed by properly authorized personnel, fully trained and certified for electrical maintenance work Method 1 (Verification with Multi-Meter) 1. Remove Power, then perform Lock-out/Tag-out (LOTO) procedures As with any electrical maintenance in the field, all systems should be stopped and de-energized, verified that power has been released, and then all power sources should be locked out and tagged out (LOTO) prior to checking the ground connectivity of the Lenze gearmotors. This is done to prevent any risk from working on energized components. WARNING: LOCK OUT AND TAG OUT ALL POWER SOURCES ACCORDING TO YOUR FACILITY S LOTO PROCEDURES BEFORE CHECKING THE LENZE GEARMOTORS. 2. Uncover Gearmotor Terminals and Remove Incoming Ground Lead With the gearmotors de-energized and all power sources properly locked-out and tagged-out, remove the terminal cover of the Lenze gearmotors to expose the nine-post terminal block used in Lenze gearmotors supplied by Bosch Rexroth (see figure 2 below). Figure 2: Exposed Nine-Post Lenze Terminal Block Disconnect the Ground Lead from the incoming power to isolate the gearmotor ground connection. Step 3 >> 2

3. Visual Check With the incoming power ground removed, visually inspect the ground jumper as much as possible: Are there any signs of it being loose or unconnected?

If there are any visual indications that there may a problem with the ground jumper, it is recommended that a full continuity test be performed, using the equipment and procedures described in DIN

3 3. Visual Check With the incoming power ground removed, visually inspect the ground jumper as much as possible: Are there any signs of it being loose or unconnected? Does the lead appear to be unstripped? If there are any visual indications that there may a problem with the ground jumper, it is recommended that a full continuity test be performed, using the equipment and procedures described in DIN standard EN Verify Continuity Between Terminal Ground Post and Frame Ground Lug Using a reliable multimeter, verify the continuity between the ground terminal post on the nine-post terminal block and the ground lug at the bottom of the terminal box (see figure 3). Using both the lowest setting on the resistance measurement AND the connectivity check, verify that there is no resistance between the ground post and lug -- there should be no more than 0.2 ohms in this measurement, and the continuity setting should give an audible ring. Figure 3: Continuity Between Ground Terminal Post and Ground Lug 5. Verify Continuity Between Terminal Ground Post and Gearmotor Frame Also verify the continuity between the ground terminal post on the nine-post terminal block and the motor frame itself (see figure 4). Using both the lowest setting on the resistance measurement AND the connectivity check, verify that there is no resistance between the ground post and gearmotor frame -- there should be no more than 0.2 ohms in this measurement, and the continuity setting should give an audible ring. Figure 4: Continuity Between Ground Terminal Post and Gearmotor Frame 3 Next Level: Full Continuity Test >>

Next Level of Investigation If this procedure has given any indication that there may a problem with the ground jumper, it is recommended that a full continuity test (Method 2) be performed, using

4 Next Level of Investigation If this procedure has given any indication that there may a problem with the ground jumper, it is recommended that a full continuity test (Method 2) be performed, using the equipment and procedures described in DIN standard EN Method 2 (Full Continuity Verification) This test is carried out based on DIN standard EN with a suitable continuity tester capable of supplying at least 10A. Higher currents up to 30A are permissible. The test time is 3 seconds and should not be significantly exceeded. The maximum permissible resistivity for the ground connector (PE) is 100 m. Please observe the operating instructions for the continuity tester. 1. Remove Power, then perform Lock-out/Tag-out procedures As with any electrical maintenance in the field, all systems should be stopped and de-energized, verified that power has been released, and then all power sources should be locked out and tagged out (LOTO) prior to checking the ground connectivity of the Lenze gearmotors. This is done to prevent any risk from working on energized components. NOTE: Follow the LOTO procedures of your facility prior to checking the Lenze gearmotors. 2. Open the terminal box. Step 3 >> 4

The image below provides an example of the status of the tester when it is switched on.

5 3. Remove the main PE wire on the terminal board screw. Incorrect internal PE-Connection 4. Switch on the tester. The image below provides an example of the status of the tester when it is switched on. The probes are not connected and is reading as an open circuit (ie the resistance is in the upper range). The LED status should indicate an ERROR (or open circuit). 5 Step 5 >>

6 5. Depending on the design of the tester, connect a probe to the unoccupied PE terminal connection screw. 6. Place the second test probe on the PE screw terminal screw in the terminal box. Step 7 >> 6

The illustration below shows the status of the tester for a PASSED test. The PE resistance is 20 m and the LED status is green, so the test has passed.

7 7. As an alternative, place the test probe on the unpainted area of the terminal box frame. WARNING: Do not let the removed main PE wire come into contact with the PE terminal board screw or motor frame. 8. Perform the continuity test. The illustration below shows the status of the tester for a PASSED test. The PE resistance is 20 m and the LED status is green, so the test has passed. The test has been passed when the measured resistance value is less than 100 m. 9. After concluding the test, replace the main PE wire. 10. Close the cover on the terminal box. 11. If the gearmotor passes the test, return the gearmotor to operation. Please contact Paul Zielbauer Technical Services Supervisor at (or paul.zielbauer@boschrexroth-us.com) with any questions or concerns regarding the results of either test. 7

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