Configuring the Motor (STAC5 / STAC6)

The STAC5 and STAC6 work best with the specially matched motors in the Recommended List. To configure the drive for one of these motor, click on the motor icon and then select a motor from the drop down list. Note that many of the motors include the suffix "par" or "ser" following the motor's model number. In the example above, the HT34-495 motor is shown, wired in parallel. Once the motor is selected, you need to set the current. The rated current for the motor you've chosen appears in the "Motor Specs" on the right and you'll normally want to use that value. If your application is particularaly heat sensitive, and you have more torque than needed, you can reduce motor heating by lowering the current. If your duty cycle is short, thereby giving the motor time to cool down between moves, you can set the current higher than the motor rating to increase the torque. Motors operated above their rated current will not operate as smoothly and if used continuously will likely overheat.

Idle current reduction automatically reduces motor heating by lowering the current when the motor is at rest. In most cases, the default value of 50% works well. Again, you can reduce motor heating further by lowering the idle current percentage.

It is also possible to adjust the idle current delay, which is the delay between the instant the motor stops moving and the actual reduction of the current. It's good to allow a little time for the motor to settle out after a move before going into idle reduction.

Load Inertia

The anti-resonance feature of the STAC drives is most effective if you can precisely set the load inertia. If you know this value, click on the first option button, enter the inertia in the box and select the units (oz-in-sec², g-cm², etc) from the list. If you don't know the exact inertia of your load, but you want to try something and see how it works, choose the second option button and enter a load to motor inertia ratio in the box.

Defining a Motor not in the Recommended List

We can't stress enough the wisdom in using one of the recommended motors. We're not just trying to make money here, we want your application to be successful and the odds of that are highest when you have a high quality motor whose torque, rotor inertia and harmonic waveform content are precisely known. Furthermore, our motors include shielded cables to reduce electrical emissions and enhance safety and come with prewired mating connectors which further reduces the risk of error.

Having stated our case, if you still insist on using a different motor, it is possible. First you'll need some detailed information from the manufacturer, including electrical specification (holding torque, rated current and rotor inertia) plus a wiring diagram. And make sure the motor is constructed from high quality magnetic materials that are suitable for operation with hihg voltage busses such as that of the STAC drives.

With this information in hand, choose the "custom motor" option and click on the Define Custom Motor button. You can enter the current, torque and inertia values into the Add New Motor dialog. For best smoothness of motion, you'll want to enter the harmonic distortion gain and phase. The Waveform Smoothing Wizard will help you determine these values, and can be accessed by clicking the "Wizard..." button.

If you plan to use the Encoder Stall Prevention feature (see the Encoder Dialog), you'll need to enter the maximum lead angle and the speed at which this "timing advance" peaks so that the drive knows when it is producing maximum torque. A typical motor produces maximum torque at low speeds with a 90° lead angle. To produce maximum torque at higher speeds, the lead angle must be increased because of inductance and back emf. Above a certain speed, further increases in lead angle produce no benefit, so you must tell the drive when to stop advancing the timing. In the example below, the lead angle is increased steadily from 90° at low speeds to 135° at 40 rev/sec, so you would enter "135 degrees at 40 rev/sec", as shown above.

If you are not using Stall Prevention, these values are not needed.