Lenze MC1000 Series Manual de usuario descargar pdf (Pagina 54)

50 13435742_EDBM101_v24

Example 2: A 480 Vac, 20 HP drive is operating a motor at 10 Hz. From the

diagram, a drive operating at 10 Hz can deliver about 75% of its output current

rating continuously. A 480 Vac, 20 HP drive’s output current rating is 27 Amps.

Therefore, the drive would be able to operate continuously at 20 Amps. The drive

would also be able to deliver 150% of that value (30 Amps) for one minute before

tripping into an OVERLOAD fault.

The “speed compensated” thermal overload is the factory default and should be

used in applications where the motor does not normally experience high loads at

low speeds for extended periods of time.

FREQUENCY (Hz)

MAXIMUM CONTINUOUS

OUTPUT CURRENT (%)

NON-COMPENSATED

SPEED COMPENSATED

10 20 30 40 50 60

100

NOTE 1: The above diagram is based on a MOTOR OL setting of 100%. For lower

MOTOR OL settings, reduce the % CURRENT values by the same percentage. For

example, if MOTOR OL is set to 75%, reduce the % CURRENT values by 25%.

Therefore, the curve shifts down, but the shape of the curve remains the same.

The “non-compensated” thermal overload circuit allows 100% current continuously,

and 150% current for one minute, at all speeds. In the example above, the motor

operating at 10 Hz without “speed-compensated” protection would be allowed

to operate continuously at 27 Amps, and could draw 40.5 Amps for one minute

before tripping. Without sucient motor cooling, this can result in motor failure due

to overheating.

The “non-compensated” circuit is selected by setting Parameter 22 - TORQUE to

CT/NOCMP. The “non-compensated” setting should only be used in applications

where the motor is properly cooled at all speeds, or the motor manufacturer has

approved the motor for full-load operation at low speeds.

NOTE 2: The operation of the motor thermal overload circuit is aected by the setting

of Parameter 34 - LOAD MLT.

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Lenze MC1000 Series Manual de usuario Pagina 54