Motor Jam Protection

Presentation

Motor jam protection provides additional protection in order to:

Detect overtorque.
Monitor mechanical malfunction.
Detect malfunctions more quickly on machines for which the motor is oversized.

Examples of machines with a significant risk of jamming: conveyors, crushers and kneaders, fans, pumps and compressors.

Description

Motor jam protection compares the value of the average motor current Iavg with the setting value of the protection Ijam pickup. If the average motor current Iavg exceeds the Ijam pickup, the protection tjam time delay is actuated.

By default, motor jam protection is not active.

After function setting, motor jam protection is:

Active in steady state.
Disabled during startup.

Operating Principle

The following figures illustrate the operating possibilities:

1 Motor current

2 Monitoring by motor jam protection

White: Not active (during startup). Green: Active (steady state)

Diagram Ι: The average motor current Iavg does not fall back below the protection Ijam pickup before the end of the tjam time delay (jammed motor). motor jam protection trips:
- A: Protection activated (change to steady state).
- B: Activation of protection time delay as soon as the pickup threshold is crossed.
- C: Protection tripped at the end of the time delay.
Diagram ΙΙ: The average motor current Iavg falls back and stays below the protection Ijam pickup before the end of the tjam time delay (occasional overload). Motor jam protection does not trip:
- B: Activation of protection time delay as soon as the pickup threshold is crossed
- D: Protection disabled.

NOTE: The SDTAM module early tripping protection function can be used to command contactor opening.

Setting the Protection

Set the Ijam pickup and the tjam time delay:

With the keypad on the MicroLogic trip unit
With EcoStruxure Power Commission software (password-protected)
By sending a setting command using the communication network (password-protected)

Ijam Pickup Setting Value

The Ijam pickup setting value is in multiples of Ir.

The pickup setting range on the keypad is 1–8 x Ir. The increment is 0.1 x Ir. The default setting value is OFF: protection not active.

The accuracy range is +/-10%.

tjam Time Delay Setting Value

The tjam time delay setting value is in seconds.

The tjam time delay setting range is 1–30 s. The increment is 1 s. The default setting value for the time delay is 5 s.