召集EMT930玩家讨论电机启动电容和调速可变电阻（可变电阻的调节... [复制链接]

其中C2这个电容器（17.5uf/50hz）随着时间而老化，会造成电机工作的震动和哼声，所以必须更换，或用小容量的电容并联上去，从而使得电容值达到1.75uf。

而在电机其中的两相之间除了那个C2电容以外，还串联2个电阻，一个R2a是固定值270，另外一个R2是一个可调节电阻，按照图纸的标值为350。
问题来了，按照图纸标注总的电阻值是620，而我今天测量后的结果总值是485，要请教各位了，图纸上那个电阻值是建议值还是必须是620，那么现在实际测量结果为总值485，是否有问题，另外这两个电阻的作用是什么。
请教各位930用家。

我是否应该将可调节电阻的阻值调整到350，从而使得2个电阻的总和等于图纸所标注的620。

按照郎兄的说法，厂标485应该是出厂值，除非被上家用家动过，否则应该不用去调整。
刚才打电话给另外一个930用家，说测出来的电阻总值是484，说明上面的说法是应该对的，谢谢。

现在就是要求证如果485是厂标，那么是不是每台930都是一样的，还是根据马达情况有不同的出厂值。
另外，按照资料，那个C2电容如果数值发生变化，就要通过并联小数值电容来提高电容值，并用示波器进行马达哼声测试。

那么为何要采用并联小电容，而不是直接将1.75电容更换呢。

以下为转载

Technical Information EMT 930

Adjusting the motor capacitor

The drive motor for the EMT 930 uses 3 phases. As the motor is driven directly with the mains

voltage, which normally uses Ground and one phase, there must be a created an additional

auxiliary phase. This is done with a resistor and a capacitor.

The capacitor (normally 1.75μF) is adjusted in the factory to a value, which gives a minimum

of hum in the machine. The adjustment is done by adding small capacitors.

During live time, the value of the original capacitor will change. This can be recognized by an

increasing hum, by a rising motor temperature and by feeling the motor vibrating.

Adjustment

Tools needed:

Millivoltmeter, Oscilloscope

How to adjust?

BE CAREFUL, BECAUSE YOU WORK WITH MAINS VOLTAGE!!!

DON’T ADJUST THE VARIABLE RESISTOR!!!

First, if your unit is equipped with a basket at the motor, unscrew the basket, to get access to

the capacitor.

Connect the voltmeter and/or the oscilloscope the output.

Put the needle in an empty groove. Now set the main switch in a position, which is normally

not fixed, between the leftmost position and the middle position (that makes the motor

running, but the turntable is not rotating). Now one can see the hum on the

voltmeter/oscilloscope.

A cheap way will be, just to add small capacitors to the large one, to find a minimum of hum.

But in some cases the value of the capacitor has grown, so that the hum will enlarge.

In that case you have to go a less cheep way and you might order a complete kit of capacitors

(including the large one) with the order number 9 930 902.

Then exchange the large capacitor, solder small capacitors in parallel to the large one, until

you reach the minimum of hum. Then fix the basket again and enjoy your hum free EMT 930.

EMT有一套维护组件，编号为9 930 902，其实是一套不同数值的电容，包括
Capacitor 0,015 μF 4 132 632
Capacitor 0,022 μF 4 132 630
Capacitor 0,047 μF 4 132 240
Capacitor 0,068 μF 4 132 621
Capacitor 0,1 μF 4 132 624
Capacitor 0,15 μF 4 132 628
Capacitor 1,75μF 4 136 081
按照资料解释，一旦测试出C2电容老化等问题，就可以在连接示波器的同时，将套件中的电容从小到大依次并联到原本的1.75uf上面，进行调整，直到马达额震动和哼声最低。