FREQUENTLY ASKED QUESTIONS
Please contact ECM with your specific questions anytime.
- What is the working ambient temperature range of the ECM machine?
Permanent magnets are generally characterized by a "maximum operating temperature" — above which point there is a loss of magnetization. This maximum temperature is significantly less than the Curie temperature, at which point all magnetization is lost. Maximum operating temperatures are dependent on the specific magnet, but the temperature range of concern is 80 C to 200 C.
Mechanical properties of the PCB suffer at around 120 C. However, high temperature withstanding and high glass-transition temperature circuit board materials are available and can be incorporated into an ECM motor, increasing temperature withstanding to 180 C, which is comparable to "H" rated induction machines. All motors need to be de-rated for high-ambient temperature operation. The limiting temperatures for ECM motor materials are not that different than those for induction machine materials (or other machine types). What is different, particularly for lower power (< 1kW) ratings, are the losses within the motor. ECM motors potentially offer efficiencies that reduce the "temperature rise" component of the derating calculation.
- Do ECM machines need ventilation?
ECM machines are not ventilated like a conventional induction machine. Contamination with air-borne magnetic materials would be difficult to remove and could lead to premature machine failure. Conventional BLDC machines, some of which are open chassis designs, share this feature.
ECM motors can be cooled passively or actively by air or water. Water-cooled ECM motors have demonstrated remarkable performance. But conventional TEFC or passive cooling is normal for an ECM machine.
- What are safe operational voltage ranges for ECM motors?
The ECM motor controller determines safe operation ranges and therefore ECM machines can be designed to accommodate any input operation and/or power conditioning.
- Do ECM machines produce harmonics and how is it compared to BLDC?
The E-circuit motor windings are staggered on layers throughout the PCB in such a way that the EMF is very nearly sinusoidal. Conventional BLDC motors with flux concentrating iron tend to produce a pronounced trapezoidal waveform.
- What is the lifetime operation of the ECM motor compared to BLDC?
End-turn insulation failures and bearing failures are the primary modes of failure in BLDC motors. Bearings are a matter of initial quality and environment, but the end-turns are where the windings in a BLDC are least supported and where the insulation is subject to the greatest stress as a matter of construction.
In contrast, ECM machines have windings that are completely constrained and encapsulated, including the end-turns. These end-turns experience no insulation stress as a matter of construction. In the event that an ECM machine stator does fail, it is a single component that can be replaced.
- What is the ECM machine’s speed and torque motor curve/characteristics? How does it compare to others?
When an ECM machine is commutated in the same fashion as a brushed DC motor, based on shaft position, the torque-speed curve is flat and linear. This curve is similar to a conventional brushless DC motor, but without the intermittent cogging torque zone.
Complete absence of cogging torque is an outstanding feature of the ECM machine.
- What are the benefits and advantages of using ECM compared to other machines?
For low-power applications, the ECM machine offers distinct efficiency and noise advantages over typical capacitor-start induction machines. Relative to BLDC motors, the advantages are durability of the windings, lack of cogging torque for applications using turn-down and efficiency. The efficiency advantage is due to the lack of iron loss. Enhanced efficiency and turn-down capability may translate to systems-level improvements such as smaller connected equipment, reduced peak loads and similar advantages.