某工厂有1台同步电动机，电气参数为：额定功率1250kW，额定交流_爱下问搜题

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问题单项选择题

某工厂有1台同步电动机，电气参数为：额定功率1250kW，额定交流三相电压6kV，额定电流0.144kA，额定起动电流倍数6倍，额定转速375r/min，电动机起动转矩与额定转矩之比为1.1，6kV母线短路容量为40MV.A，母线上预接负荷的无功功率为1Mvar，要求起动时母线电压不低于额定电压的85%。计算采用全压起动和采用电抗器降压起动的有关参数。

验算全压起动时6kV母线电压相对值为()，()采用全压起动。

A．0.87，可以

B．0.87，不能

C．0.82，可以

D．0.82，不能

答案

参考答案：D

单项选择题

从同一正态总体中随机抽取多个样本，用样本均数来猜测总体均数的可信度，下列()得到的可信度高

A．标准误大的样本

B．标准差小的样本

C．标准误小的样本

D．均数大的样本

E．均数小的样本

完形填空

Birthdays often bring surprises. But this year’s surprise on the birthday of the great British playwright William Shakespeare is __21__ one of the most surprising.
On April 22, one day before his 441^st birthday anniversary, experts __22__ that one of the most recognizable __23__ of William Shakespeare is a fake (赝品).
This __24__ that we no longer have a good __25__ of what Shakespeare looked like. “It’s very possible that many pictures of Shakespeare are unreliable because many of them are __26__ of this one,” said an expert from Britain’s National Portrait Gallery.
The _27_ comes after four months of testing. Experts from the gallery say the image — commonly known as the “Flower portrait” — was actually __28__ in the 1800s, two centuries __29_ Shakespeare’s death.
The art experts who work at the gallery say they used modern chemistry technology to __30__ the paint on the picture. These checks found traces (痕迹) of paint deep in the picture __31__ about 1814.
Shakespeare __32__ in 1616, and the date that appears on the portrait is 1609.
“We now think the portrait dates back to around 1818 to 1840. This was __33__ there was a new interest in Shakespeare’s__ 34__ ,” Tanya Cooper, the gallery’s 16^th century curator (馆长) said.
The __35__ picture has often been used as a cover for __36__ of his plays. It is called the “Flower portrait” because one of its __37__, Desmond Flower, gave it to the Royal Shakespeare Company.
“There have always been __38__ about the authenticity (真实性) of the painting,” said David Howells, curator for the Royal Shakespeare Company.
“Now we know the truth, we can put the image in its proper place in the history of Shakespearean portraiture (画像技法),” he said.
Two other images of Shakespeare are also being studied as part of the investigation and the results will __39__later in May. But for now what Shakespeare really looked like will remain a __40__.

B．masterpieces

B．productions

A．looking back

B．dating from

C．getting along

D．starting with

A．requirements

B．collections

C．consequences

D．playwrights