Hello Friends;

I have one question and wandering for its answer. In the literature of AC/DC drives, a term “speed range” (say 50:1 open loop and 200:1 when closed loop) describes, can anyone explain about it? I am not known about it.

For refrenece, please see the attached image or click the following link;

http://www.joliettech.com/dc_drive_types.htm

No conception. Somewhat fuzzy short articles - seems they have confused, by omission, basic and maximal speeds in their explanations of the constant power/torque.
Best regards.

Hello yuri,

I have read about "drive speed range" from two to three places. For example, click on the bellow link where you would see that rockwell automation too quoted drive speed range after tables.

Rockwellautomation

Looking forward for a detailed answer from someone.

Hi Yuri: Here is the definition for speed range:

The minimum and maximum speeds at which a motor must operate under constant or variable torque load conditions.
For example:
A 4:1 speed range for a motor with a top speed of 1800 rpm means that the motor must be able to operate as low as 450 rpm and still remain within regulation specifications. The controllable speed range of a motor is limited by the ability to deliver required torque below base speed without additional cooling.
Hope this helped you, George

Thanks ggalea;

For example, there has been quoted with a drive 200:1 speed range. If motor is 1800rpm then it means motor can run at 9rpm within regulation spec? Some drives manufacturers quote 1000:1 (see in the link posted in my previous mail), what its means?


Discussion always leads to everyone to the right point.

Yuri: These are from my notes:

Mostly, these speed ranges are applicable to Constant torque loads
Applications include: Conveyors, elevators, hoists, extruders, positive displacement pumps, mixers and converting equipment.

Torque remains constant throughout the range of operation, and extra care should be taken in the proper application of motors, especially at very low speeds. Most constant torque (C.T.) applications don't require operation below 10:1 (i.e. 6 Hz operation on a 60 Hz motor), but an increasing number of applications historically reserved for servo and/or stepper systems are being served with motors capable of operation beyond 20:1…even up to 2000:1 (zero speed, constant torque).

Applications requiring greater than 20:1 C.T. are ideal for certain electric that advertise these type of motor specs.
These motors provide full rated torque within their listed speed range, without exceeding a Class F temperature rating while under inverter power (many operate at Nema Design Class B insulation). Ratings have been developed, based on extensive testing on IGBT inverters, set at a minimum 3 KHz (or equivalent) carrier frequency. Carrier frequency is the switching frequency of the IGBTs. The higher you go the hotter the motor gets deep inside the windings. If you are going to take the temperature of the motor with a temp gun, always wait until the motor is powered OFF, wait about 5 minutes, then take the temperature of the motor skin. This allows for the heat to egress to the outside skin of the motor hence you get the true temp reading. Taking the temp of a running motor is useless.

These vector-duty and inverter-duty motors are designed for operation at 150% of rated load for one minute, up to the base speed of the motor (overload capability declines to 100% as the motor reaches maximum constant HP speed). These motors accommodate constant horsepower operation to 1-1/2 to 2 times base speed, subject to the motor's maximum safe mechanical speed limit. Please refer to product technical and performance specifications for each motor's capability. Motors rated for zero RPM continuous duty (1000:1 or 2000:1) must be powered by vector drives to produce rated torque without overheating. Optimum zero speed and low-speed full torque performance may require a closed loop vector drive (with encoder feedback). The low speeds and having 100% torque available at 0.001hz (essentially zero speed) means the motor MUST be cooled by a fan blower kit on the bell end, thi9s is a muffin fan that is always on blowing at full speed regardless of the motors speed.
Yuri, my fee is 1 beer OK?
Cheers!,
George

Dear ggalea;

Thanks for a nice explanation. I have understood now about drive speed range.