Toshiba G7 VFD
Toshiba G7 Adjustable Speed Drive (ASD)
The Toshiba G7 ASD is a sophisticated variable frequency drive designed to control the speed of AC motors with precision. It offers advanced features to optimize motor performance and protect against common operational issues.
Key Features:
Motor Autotuning:
Addresses minor variations in motor production through autotuning, which measures and stores motor parameters to optimize ASD response to specific load and operational requirements.
Parameters measured include rotor resistance, stator resistance, excitation inductance, rotational inertia, and leakage inductance.
A factory-loaded table of motor parameters is also available for various motor types.
Pulse Width Modulation (PWM) Operation:
Utilizes sinusoidal PWM control to generate an output current waveform that closely resembles a sine wave, though slight distortion may cause increased motor heat, noise, and vibration.
Low Speed Operation:
Operating at lower speeds may reduce motor cooling efficiency. It's recommended to use a Toshiba VF motor designed for ASD use when operating at low speeds and rated torque continuously.
Overload Protection Adjustment:
Monitors output current to detect and protect against overload conditions. The default setting is the maximum rated current of the ASD and may need adjustment to match the motor rating.
Operation Above 60 Hz:
Operating a motor above 60 Hz may increase noise, vibration, and risk exceeding motor or bearing limits, potentially voiding the motor warranty.
Power Factor Correction:
Do not connect power factor correction capacitors or surge absorbers to the ASD output, as it may cause malfunctions or damage.
Light Load Conditions:
Operating under light load or with low inertia may cause instability. Lowering the carrier frequency can compensate for this condition.
Motor/Load Combinations:
Certain motor/load combinations may result in unstable operation. Adjustments to the carrier frequency or control mode may be necessary for stability.
Load-produced Negative Torque:
Negative torque from an overhauling load can cause nuisance tripping. Dynamic braking can minimize these effects by converting regenerated energy into heat.
Motor Braking:
To achieve an immediate stop, braking systems like DC Injection Braking and Dynamic Braking can be used.
ASD Characteristics:
Over-current protection is designed to prevent trips by operating within specified current ranges. Adjustments may be necessary for applications with motors rated significantly lower than the ASD's maximum current rating.
ASD Capacity:
The ASD should not be used with a motor significantly larger than its capacity to avoid high-output peak currents and nuisance tripping.
Using Vector Control:
Enables high torque production over the entire operating range, even at very low speeds. Feedback increases speed accuracy for precise control applications.
Local/Remote Operation:
The ASD can be operated in Local or Remote modes, with specific considerations for maintaining control during mode changes.
Installation and Connections:
Proper installation and grounding are essential for safe and efficient operation. Separate conduits and grounding conductors for input, output, and control lines are recommended.
By incorporating these features, the Toshiba G7 ASD provides reliable and efficient control of AC motors, enhancing performance and protecting against common operational issues.
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